2024/04/08 更新

写真a

オオツカ ユウイチ
大塚 雄一
OTSUKA, Yuichi
所属
宇宙地球環境研究所 基盤研究部門 電磁気圏研究部 准教授
大学院担当
大学院理学研究科
職名
准教授
連絡先
メールアドレス
外部リンク

学位 1

  1. 博士(工) ( 1999年3月   京都大学 ) 

研究キーワード 3

  1. 電離圏 大気光 全電子数 GPS GNSS

  2. 電離圏物理学

  3. 超高層大気物理学

研究分野 3

  1. その他 / その他  / 超高層物理学

  2. 自然科学一般 / 宇宙惑星科学

  3. その他 / その他  / 超高層物理学

現在の研究課題とSDGs 2

  1. GPS・レーダー・光学観測による中低緯度電離圏の研究

  2. 電離圏のGNSSへの影響に関する研究

経歴 1

  1. 名古屋大学 宇宙地球環境研究所・准教授

    2015年10月 - 現在

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    国名:日本国

学歴 2

  1. 京都大学   工学研究科

    1996年4月 - 1999年3月

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    国名: 日本国

  2. 京都大学   大学院工学研究科

    1996年4月 - 1998年3月

所属学協会 5

  1. 地球電磁気・地球惑星圏学会

  2. 米国地球物理学連合

  3. 測位航法学会

  4. 測位航法学会

  5. 地球電磁気・地球惑星圏学会

受賞 13

  1. Excellent Reviewers 2021

    2022年1月   Earth, Planets and Space  

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    受賞区分:学会誌・学術雑誌による顕彰 

  2. Excellent Reviewers 2020

    2021年1月   Earth, Planets and Space  

  3. Advances in Space Research: Top Reviewer 2019

    2020年6月   Committee on Space Research  

  4. 田中舘賞

    2019年10月   地球電磁気・地球惑星圏学会  

  5. AGU’s Outstanding Reviewers of 2018, Radio Science

    2019年5月   米国地球物理学連合  

  6. Advances in Space Research: Top Reviewers of 2017

    2018年8月  

  7. Editors' Citations for Excellence in Refereeing, Radio Science

    2012年10月   米国地球物理学連合  

    大塚 雄一

  8. 2011年 Radio Science 誌優秀論文審査賞

    2011年   米国地球物理連合  

  9. 2009年 Geophysical Research Letters誌優秀論文審査賞

    2010年9月   米国地球物理連合  

  10. Editors' Citations for Excellence in Refereeing, Geophysical Research Letters

    2010年5月   米国地球物理学連合  

    大塚 雄一

  11. EPS Award

    2009年5月   Earth, Planets and Space (EPS)  

    大塚 雄一

  12. 地球電磁気・地球惑星圏学会 大林奨励賞

    2005年9月   地球電磁気・地球惑星圏学会  

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    受賞国:日本国

  13. 大林奨励賞

    2005年9月   地球電磁気・地球惑星圏学会   熱圏電離圏における大気・プラズマ結合の研究

    大塚 雄一

▼全件表示

 

論文 466

  1. Spatial relationship of nighttime medium-scale traveling ionospheric disturbances and F region field-aligned irregularities observed with two spaced all-sky airglow imagers and the middle and upper atmosphere radar 査読有り

    Otsuka, Y., K. Shiokawa, T. Ogawa, T. Yokoyama, and M. Yamamoto

    J. Geophys. Res.   114 巻   頁: A05302, doi:10.1029/2008JA013902   2009年5月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) and field-aligned irregularities (FAIs) in the F region by using two all-sky airglow imagers and the MU radar. MSTIDs propagating southwestward were observed simultaneously in 630-nm airglow images over Sakata (39.0N, 139.9E) and Shigaraki (34.9N, 136.1E), Japan on the night of June 16, 2004. By using all-sky images over both sites, we estimated the altitude of the airglow layer to be 260 km by the triangulation method.
    During the MSTID event, FAIs in the F region were observed
    by making multibeam measurements with the MU radar at Shigaraki. In order to investigate the spatial relationship between the MSTIDs and FAIs, the FAIs were mapped onto the 630-nm airglow layer (altitude: 260 km) along the geomagnetic field lines. We found that FAIs with intense (weak) signal-to-noise ratio (SNR) coincided with the airglow depletion (enhancement) caused by the MSTIDs. FAI velocity obtained from a combination of the Doppler velocities on the three radar beams oscillated in the NW-SE direction with an amplitude of approximately 82 m/s. The FAI velocity was northwestward (southeastward) at the airglow depletion (enhancement). The directions of the FAI velocity
    were consistent with those of the ExB drifts caused by the polarized electric fields associated with the MSTIDs.
    The northeastward polarized electric field at the airglow depletion region strengthened the background eastward
    effective electric field, and drove the gradient drift instability generating FAIs. This might be the reason why the FAIs preferred to occur at the airglow depletion region.

  2. VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia 査読有り

    Otsuka, Y., T. Ogawa, and Effendy

    Earth Planets Space   61 巻   頁: 431-437   2009年5月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report the response of the ionosphere to the large erthquake that occurred in West Sumatra, Indonesia, at 0058 UT on December 26, 2004. We have analyzed Global Positioning System (GPS) data obtained at two sites in Sumatra and at three sites in Thailand to investigate total electron content (TEC) variations. Between 14 and 40 min after the earthquake,
    TEC enhancements of 1.6--6.9 TEC units (TECU) were observed
    at subionospheric points located 360-2000 km north of the epicenter. From the time delays of the observed TEC enhancements, we find that the TEC enhancements propagated northward from the epicenter. The time delays between the earthquake and rapid increases in TEC, which occurred near the epicenter, are consistent with the idea that acoustic waves generated by the earthquake propagated into the ionosphere at the speed of sound to cause the TEC variations.
    A small TEC enhancement of 0.6 TECU was observed south of the epicenter, while no TEC enhancements were seen east of the epicenter. From a model calculation, we find that this directivity of the TEC variations with respect to the azimuth from the epicenter could be caused partially by the directivity in the response of the electron density variation
    to the acoustic waves in the neutral atmosphere.

  3. GPS detection of total electron content variations over Indonesia and Thailand following the 26 December 2004 earthquake 査読有り

    Otsuka, Y., N. Kotake, T. Tsugawa, K. Shiokawa, T. Ogawa, Effendy, S. Saito, M. Kawamura, T. Maruyama, N. Hemmakorn, and T. Komolmis

    Earth, Planets and Space   58 巻   頁: 159-165   2006年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  4. *Geomagnetic conjugate observations of medium-scale traveling ionospheric disturbances at midlatitude using all-sky airglow imagers 査読有り

    Otsuka, Y., K. Shiokawa, T. Ogawa, and P. Wilkinson

    Geophys. Res. Lett.   31 巻 ( L15803 ) 頁: doi:10.1029/2004GL020262   2004年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report for the first time simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) at geomagnetic conjugate points in both hemispheres, using two all-sky airglow imagers at midlatitudes. A 630-nm all-sky CCD imager at Sata, Japan, detected MSTIDs with a wavefront elongated from NW to SE on the night of August 9, 2002. During this event, MSTIDs with a wavefront elongated from SW to NE were observed at the geomagnetic conjugate point, Darwin, Australia. The MSTID structures mapped from Darwin to its magnetic conjugate points along the geomagnetic field lines B coincide closely with those in the Sata images. This result suggests that polarization electric field (Ep) plays an important role in the generation of MSTIDs. Ep maps along B and moves the F region plasma upward or downward by ExB drifts, causing plasma density perturbations with structures mirrored in the northern and southern hemispheres.

  5. *A new technique for mapping of total electron content using GPS network in Japan 査読有り

    Otsuka, Y., T. Ogawa, A. Saito, T. Tsugawa, S. Fukao, and S. Miyazaki

    Earth, Planets, and Space   54 巻   頁: 63-70   2002年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  6. Performance of the double-thin-shell approach for studying nighttime medium-scale traveling ionospheric disturbances using two dense GNSS observation networks in Japan

    Fu, WZ; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S

    EARTH PLANETS AND SPACE   76 巻 ( 1 )   2024年1月

  7. Statistical Analysis of Global and Regional Ionospheric Total Electron Content (TEC) Using Extreme Value Distributions

    Emmela, S; Ratnam, DV; Otsuka, Y; Shinbori, A; Sori, T; Nishioka, M; Perwitasari, S

    IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING   62 巻   2024年

  8. Assessing the potential of ionosonde for forecasting post-sunset equatorial spread F: an observational experiment in Southeast Asia

    Abadi, P; Ahmad, UA; Otsuka, Y; Jamjareegulgarn, P; Almahi, A; Perwitasari, S; Supriadi, S; Harjupa, W; Septiawan, RR

    EARTH PLANETS AND SPACE   75 巻 ( 1 )   2023年12月

  9. An Extreme Value Analysis of Long-Term GNSS Ionospheric Total Electron Content Data Observed at Japan Grid Point Location (34.95° N and 134.05° E) 査読有り

    Emmela, S; Ratnam, DV; Otsuka, Y; Shinbori, A; Sori, T; Nishioka, M; Perwitasari, S

    IEEE GEOSCIENCE AND REMOTE SENSING LETTERS   20 巻   2023年11月

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    記述言語:英語  

    DOI: 10.1109/LGRS.2023.3292593

    Web of Science

  10. Equinoctial asymmetry of plasma bubble occurrence and electric field at evening: GPS and ionosonde measurements in Southeast Asia 査読有り

    Otsuka, Y; Abadi, P; Hozumi, K; Almahi, A

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   252 巻   2023年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2023.106136

    Web of Science

  11. Daytime Medium Scale Traveling Ionospheric Disturbances (MSTIDS) Over the Andes Mountains at Equatorial and Low Magnetic Latitudes

    Figueiredo, CAOB; Wrasse, CM; Vadas, S; Takahashi, H; Otsuka, Y; Nyassor, PK; Shiokawa, K; Paulino, I; Barros, D

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 10 )   2023年10月

  12. Responses of the African-European equatorial-, low-, mid-, and high-latitude ionosphere to geomagnetic storms of 2013, 2015 St Patrick's Days, 1 June 2013, and 7 October 2015 査読有り

    Akala, AO; Afolabi, RO; Otsuka, Y

    ADVANCES IN SPACE RESEARCH   72 巻 ( 3 ) 頁: 775 - 789   2023年8月

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    記述言語:英語  

    DOI: 10.1016/j.asr.2022.10.029

    Web of Science

  13. Equatorial plasma bubble intensities across longitudinal sectors of the globe using GNSS observations 査読有り

    Okoh, D; Shiokawa, K; Otsuka, Y; Rabiu, B; Habarulema, JB; Migoya-Orue, Y; Cesaroni, C

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   249 巻   2023年8月

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    記述言語:英語  

    DOI: 10.1016/j.jastp.2023.106097

    Web of Science

  14. Ionospheric disturbances over South America related to Tonga volcanic eruption 査読有り

    Takahashi, H; Figueiredo, CAOB; Barros, D; Wrasse, CM; Giongo, GA; Honda, RH; Vital, LFR; Resende, LCA; Nyassor, PK; Ayorinde, TT; Carmo, CS; Padua, MB; Otsuka, Y

    EARTH PLANETS AND SPACE   75 巻 ( 1 )   2023年5月

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    記述言語:英語  

    DOI: 10.1186/s40623-023-01844-1

    Web of Science

  15. Day-to-day variability of the equatorial ionosphere in Asian sector during August-October 2019 査読有り

    Liu, HX; Otsuka, Y; Hozumi, K; Yu, T

    FRONTIERS IN ASTRONOMY AND SPACE SCIENCES   10 巻   2023年5月

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    記述言語:英語  

    DOI: 10.3389/fspas.2023.1198739

    Web of Science

  16. First Detection of Midlatitude Plasma Bubble by SuperDARN During a Geomagnetic Storm on May 27 and 28, 2017 査読有り

    Sori, T; Shinbori, A; Otsuka, Y; Nishioka, M; Perwitasari, S; Nishitani, N

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 4 )   2023年4月

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    記述言語:英語  

    DOI: 10.1029/2022JA031157

    Web of Science

  17. Multi-Event Conjugate Measurements of the SAR Arc Detachment From the Auroral Oval Using DMSP Satellites and an All-Sky Camera at Athabasca, Canada 査読有り

    Gololobov, A; Shiokawa, K; Baishev, D; Inaba, Y; Otsuka, Y; Connors, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 4 )   2023年4月

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    記述言語:英語  

    DOI: 10.1029/2022JA030544

    Web of Science

  18. Dependence of Ionospheric Responses on Solar Wind Dynamic Pressure During Geomagnetic Storms Using Global Long-Term GNSS-TEC Data 査読有り

    Sori, T; Shinbori, A; Otsuka, Y; Nishioka, M; Perwitasari, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 3 )   2023年3月

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    記述言語:英語  

    DOI: 10.1029/2022JA030913

    Web of Science

  19. Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes 査読有り

    Chau, JL; Longley, WJ; Reyes, PM; Pedatella, NM; Otsuka, Y; Stolle, C; Liu, H; England, SL; Vierinen, JP; Milla, MA; Hysell, DL; Oppenheim, MM; Patra, A; Lehmacher, G; Kudeki, E

    FRONTIERS IN ASTRONOMY AND SPACE SCIENCES   10 巻   2023年2月

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    記述言語:英語  

    DOI: 10.3389/fspas.2023.1091319

    Web of Science

  20. Tandem Observations of Nighttime Mid-Latitude Topside Ionospheric Perturbations 査読有り

    Song, H; Park, J; Jin, YQ; Otsuka, Y; Buchert, S; Lee, J; Yi, Y

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   21 巻 ( 2 )   2023年2月

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    記述言語:英語  

    DOI: 10.1029/2022SW003312

    Web of Science

  21. Ionospheric Modulation by EMIC Wave-Driven Proton Precipitation: Observations and Simulations

    Tian, XB; Yu, YQ; Gong, F; Ma, LX; Cao, JB; Solomon, SC; Shreedevi, PR; Shiokawa, K; Otsuka, Y; Oyama, S; Miyoshi, Y

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 1 )   2023年1月

  22. Relationship between geomagnetic storms and occurrence of ionospheric irregularities in the west sector of Africa during the peak of the 24th solar cycle

    Ondede, GO; Rabiu, AB; Okoh, D; Baki, P; Olwendo, J; Shiokawa, K; Otsuka, Y

    FRONTIERS IN ASTRONOMY AND SPACE SCIENCES   9 巻   2022年11月

  23. Localized mesospheric ozone destruction corresponding to isolated proton aurora coming from Earth's radiation belt

    Ozaki Mitsunori, Shiokawa Kazuo, Kataoka Ryuho, Mlynczak Martin, Paxton Larry, Connors Martin, Yagitani Satoshi, Hashimoto Shion, Otsuka Yuichi, Nakahira Satoshi, Mann Ian

    SCIENTIFIC REPORTS   12 巻 ( 1 )   2022年10月

  24. Three-Dimensional Fourier Analysis of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances Observed in Airglow Images in Hawaii Over Three Years

    Naito Hideto, Shiokawa Kazuo, Otsuka Yuichi, Fujinami Hatsuki, Tsuboi Takuma, Sakanoi Takeshi, Saito Akinori, Nakamura Takuji

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   127 巻 ( 10 )   2022年10月

  25. Statistical Study of Subauroral Arc Detachment at Athabasca, Canada: New Insights on STEVE

    Yadav, S; Shiokawa, K; Otsuka, Y; Connors, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   127 巻 ( 9 )   2022年9月

  26. Geomagnetic conjugacy of plasma bubbles extending to mid-latitudes during a geomagnetic storm on March 1, 2013

    Sori, T; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S

    EARTH PLANETS AND SPACE   74 巻 ( 1 )   2022年8月

  27. Electromagnetic conjugacy of ionospheric disturbances after the 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption as seen in GNSS-TEC and SuperDARN Hokkaido pair of radars observations

    Shinbori Atsuki, Otsuka Yuichi, Sori Takuya, Nishioka Michi, Perwitasari Septi, Tsuda Takuo, Nishitani Nozomu

    EARTH PLANETS AND SPACE   74 巻 ( 1 )   2022年7月

  28. A confirmation of vertical acoustic resonance and field-aligned current generation just after the 2022 Hunga Tonga Hunga Ha'apai volcanic eruption

    Iyemori, T; Nishioka, M; Otsuka, Y; Shinbori, A

    EARTH PLANETS AND SPACE   74 巻 ( 1 )   2022年6月

  29. On the Role of E-F Region Coupling in the Generation of Nighttime MSTIDs During Summer and Equinox: Case Studies Over Northern Germany

    Sivakandan, M; Martinis, C; Otsuka, Y; Chau, JL; Norrell, J; Mielich, J; Conte, JF; Stolle, C; Rodríguez-Zuluaga, J; Shinbori, A; Nishioka, M; Tsugawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   127 巻 ( 5 )   2022年5月

  30. Modeling Post-Sunset Equatorial Spread-F Occurrence as a Function of Evening Upward Plasma Drift Using Logistic Regression, Deduced from Ionosondes in Southeast Asia

    Abadi, P; Ahmad, UA; Otsuka, Y; Jamjareegulgarn, P; Martiningrum, DR; Faturahman, A; Perwitasari, S; Saputra, RE; Septiawan, RR

    REMOTE SENSING   14 巻 ( 8 )   2022年4月

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  31. Statistical Behavior of Large-Scale Ionospheric Disturbances From High Latitudes to Mid-Latitudes During Geomagnetic Storms Using 20-yr GNSS-TEC Data: Dependence on Season and Storm Intensity

    Shinbori, A; Otsuka, Y; Sori, T; Tsugawa, T; Nishioka, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   127 巻 ( 1 )   2022年1月

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    記述言語:日本語  

    DOI: 10.1029/2021JA029687

    Web of Science

  32. Variations of Zonal Wind Velocity in the Thermosphere Observed at Southeast Asian Sector During Quiet and Active Geomagnetic Days

    Sarudin, I; Hamid, NSA; Abdullah, M; Rusli, FNSM; Otsuka, Y; Shiokawa, K; Yatini, C; Komonjinda, S; Somboon, E

    JURNAL FIZIK MALAYSIA   43 巻 ( 1 ) 頁: 10025 - 10035   2022年

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  33. Xtend, the Soft X-ray Imaging Telescope for the X-ray Imaging and Spectroscopy Mission (XRISM)

    Mori, K; Tomida, H; Nakajima, H; Okajima, T; Noda, H; Tanaka, T; Uchida, H; Hagino, K; Kobayashi, SB; Suzuki, H; Yoshida, T; Murakami, H; Uchiyama, H; Nobukawa, M; Nobukawa, KK; Yoneyama, T; Matsumoto, H; Tsuru, TG; Yamauchi, M; Hatsukade, I; Ishida, M; Maeda, Y; Hayashi, T; Tamura, K; Boissay-Malaquin, R; Sato, T; Hiraga, J; Kohmura, T; Yamaoka, K; Dotani, T; Ozaki, M; Tsunemi, H; Kanemaru, Y; Sato, J; Takaki, T; Terada, Y; Miyazaki, K; Kusunoki, K; Otsuka, Y; Yokosu, H; Yonemaru, W; Asahina, Y; Asakura, K; Yoshimoto, M; Ode, Y; Sato, J; Hakamata, T; Aoyagi, M; Aoki, Y; Tsunomachi, S; Doi, T; Aoki, D; Fujisawa, K; Kitajima, M; Hayashida, K

    SPACE TELESCOPES AND INSTRUMENTATION 2022: ULTRAVIOLET TO GAMMA RAY   12181 巻   2022年

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  34. An experimental investigation into the possible connections between the zonal neutral wind speeds and equatorial plasma bubble drift velocities over the African equatorial region

    Okoh, DI; Rabiu, AB; Shiokawa, K; Otsuka, Y; Wu, Q; Seemala, GK; Katamzi-Joseph, ZT

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   220 巻   2021年9月

  35. Preface to the Special Issue on recent advances in the study of Equatorial Plasma Bubbles and Ionospheric Scintillation

    Otsuka, Y; Spogli, L; Ram, ST; Li, GZ

    EARTH AND PLANETARY PHYSICS   5 巻 ( 5 ) 頁: 365 - 367   2021年9月

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    記述言語:日本語  

    DOI: 10.26464/epp2021050

    Web of Science

  36. Plasma depletions lasting into daytime during the recovery phase of a geomagnetic storm in May 2017: Analysis and simulation of GPS total electron content observations

    Otsuka, Y; Shinbori, A; Sori, T; Tsugawa, T; Nishioka, M; Huba, JD

    EARTH AND PLANETARY PHYSICS   5 巻 ( 5 ) 頁: 427 - 434   2021年9月

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    記述言語:日本語  

    DOI: 10.26464/epp2021046

    Web of Science

  37. Multi-instrument study of longitudinal wave structures for plasma bubble seeding in the equatorial ionosphere

    Takahashi, H; Essien, P; Figueiredo, CAO; Wrasse, CM; Barros, D; Abdu, MA; Otsuka, Y; Shiokawa, K; Li, GZ

    EARTH AND PLANETARY PHYSICS   5 巻 ( 5 ) 頁: 368 - 377   2021年9月

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    記述言語:日本語  

    DOI: 10.26464/epp2021047

    Web of Science

  38. L-Band Synthetic Aperture Radar Observation of Ionospheric Density Irregularities at Equatorial Plasma Depletion Region

    Sato, H; Kim, JS; Otsuka, Y; Wrasse, CM; de Paula, ER; de Souza, JR

    GEOPHYSICAL RESEARCH LETTERS   48 巻 ( 16 )   2021年8月

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    記述言語:日本語  

    DOI: 10.1029/2021GL093541

    Web of Science

  39. PSTEP: project for solar-terrestrial environment prediction

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  76. Label-free observation of tissues by high-speed stimulated Raman spectral microscopy and independent component analysis

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  77. Small-scale ionospheric delay variation associated with plasma bubbles studied with GNSS and optical measurements and its impact on GBAS

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    PROCEEDINGS OF THE 26TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS 2013)     頁: 1869 - 1874   2013年

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  78. High-speed molecular spectral imaging of tissue with stimulated Raman scattering

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  79. A comparative study of equatorial daytime vertical E x B drift in the Indian and Indonesian sectors based on 150 km echoes

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年11月

  80. Observation of equatorial nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow images over 7 years

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  81. Motion of high-latitude nighttime medium-scale traveling ionospheric disturbances associated with auroral brightening

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  82. Response of low-latitude ionosphere to medium-term changes of solar and geomagnetic activity

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年8月

  83. Significance of C4d deposition in antibody-mediated rejection

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  84. GPS total electron content variations associated with poleward moving Sun-aligned arcs

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年5月

  85. Polarization of Pc1/EMIC waves and related proton auroras observed at subauroral latitudes

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年2月

  86. Ionospheric and thermospheric storms at equatorial latitudes observed by CHAMP, ROCSAT, and DMSP

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年1月

  87. On postmidnight low-latitude ionospheric irregularities during solar minimum: 2. C/NOFS observations and comparisons with the Equatorial Atmosphere Radar

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年11月

  88. New aspects of thermospheric and ionospheric storms revealed by CHAMP

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年7月

  89. Decay of polar cap patch

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年5月

  90. Vertical connection from the tropospheric activities to the ionospheric longitudinal structure simulated by a new Earth's whole atmosphere-ionosphere coupled model

    Jin H., Miyoshi Y., Fujiwara H., Shinagawa H., Terada K., Terada N., Ishii M., Otsuka Y., Saito A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年1月

  91. Dynamic temporal evolution of polar cap tongue of ionization during magnetic storm

    Hosokawa K., Tsugawa T., Shiokawa K., Otsuka Y., Nishitani N., Ogawa T., Hairston M. R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年12月

  92. Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年9月

  93. Finite-Temperature Properties across the Charge Ordering Transition-Combined Bosonization, Renormalization Group, and Numerical Methods-

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    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 巻 ( 9 )   2010年9月

  94. Large-scale traveling ionospheric disturbance observed by superDARN Hokkaido HF radar and GPS networks on 15 December 2006

    Hayashi H., Nishitani N., Ogawa T., Otsuka Y., Tsugawa T., Hosokawa K., Saito A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年6月

  95. A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年2月

  96. Reorganization of polar cap patches through shears in the background plasma convection

    Hosokawa K., St-Maurice J. -P., Sofko G. J., Shiokawa K., Otsuka Y., Ogawa T.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年1月

  97. Spatial relationship of nighttime medium-scale traveling ionospheric disturbances and F region field-aligned irregularities observed with two spaced all-sky airglow imagers and the middle and upper atmosphere radar

    Otsuka Y., Shiokawa K., Ogawa T., Yokoyama T., Yamamoto M.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年5月

  98. Motion of polar cap patches: A statistical study with all-sky airglow imager at Resolute Bay, Canada

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年4月

  99. Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities

    Ogawa T., Nishitani N., Otsuka Y., Shiokawa K., Tsugawa T., Hosokawa K.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

  100. Super plasma fountain and equatorial ionization anomaly during penetration electric field

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

  101. Relationship between polar cap patches and field-aligned irregularities as observed with an all-sky airglow imager at Resolute Bay and the PolarDARN radar at Rankin Inlet

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

  102. Three-dimensional simulation of the coupled Perkins and E-s-layer instabilities in the nighttime midlatitude ionosphere

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

  103. Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations

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    ANNALES GEOPHYSICAE   27 巻 ( 4 ) 頁: 1625 - 1629   2009年

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    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 397 - 410   2009年

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    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 479 - 491   2009年

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  106. Relative effects of electric field and neutral wind on positive ionospheric storms

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    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 439 - 445   2009年

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    FUTURE PERSPECTIVES OF SPACE PLASMA AND PARTICLE INSTRUMENTATION AND INTERNATIONAL COLLABORATIONS   1144 巻   頁: 212 - +   2009年

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  108. Zonal asymmetry of daytime 150-km echoes observed by Equatorial Atmosphere Radar in Indonesia

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    ANNALES GEOPHYSICAE   27 巻 ( 3 ) 頁: 967 - 974   2009年

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  109. VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia

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    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 431 - 437   2009年

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  110. Prospective multicenter trial comparing repeated immunosuppressive therapy with stem-cell transplantation from an alternative donor as second-line treatment for children with severe and very severe aplastic anemia

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  111. Quantum dot sensitized solar cells

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    2008 2ND IEEE INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1-3     頁: 160 - +   2008年

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  112. Efficacy of STI571 for a patient with metastatic gastrointestinal stromal tumor

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  113. Inhibition of platelet adherence to mononuclear cells by alpha-tocopherol - Role of P-selectin

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  114. Usefulness of magnifying endoscopy in the diagnosis of early gastric cancer

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  115. Novel gene encoding a Ca2+-binding protein and under hexokinase-dependent sugar regulation

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    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY   67 巻 ( 2 ) 頁: 347 - 353   2003年2月

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  116. Vitamin E inhibits lysophosphatidylcholine-induced endothelial dysfunction and platelet activation

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    ANTIOXIDANTS & REDOX SIGNALING   4 巻 ( 5 ) 頁: 791 - 798   2002年10月

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  117. Platelet GPIIb/IIIa is activated and platelet-leukocyte coaggregates formed in vivo during hemodialysis

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    NEPHRON   90 巻 ( 4 ) 頁: 391 - 400   2002年4月

  118. Changes in Mac-1 and CD14 expression on monocytes and serum soluble CD14 level during push/pull hemodiafiltration

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    NEPHRON   90 巻 ( 3 ) 頁: 273 - 281   2002年3月

  119. Numerical simulation of gas flow through sand core

    Maeda, Y; Nomura, H; Otsuka, Y; Tomishige, H; Mori, Y

    INTERNATIONAL JOURNAL OF CAST METALS RESEARCH   15 巻 ( 4 ) 頁: 441 - 444   2002年

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  120. Imaging observations of midlatitude ionospheric disturbances during the geomagnetic storm of February 12, 2000

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A11 ) 頁: 24481 - 24492   2001年11月

  121. CD31 expression on leukocytes is downregulated in vivo during hemodialysis

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    NEPHRON   89 巻 ( 2 ) 頁: 153 - 160   2001年10月

  122. The assessment of vertical and lateral invasion of early gastric cancer by magnifying endoscopy

    Otsuka, Y; Goto, H; Niwa, Y; Ohmiya, N; Kamiya, K; Sakata, T; Ando, N; Ito, B; Sasaki, Y; Hayakawa, T

    GASTROINTESTINAL ENDOSCOPY   53 巻 ( 5 ) 頁: AB212 - AB212   2001年4月

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  123. The assessment of vertical and lateral invasion of early gastric cancer by magnifying endoscopy

    Otsuka Y, Goto H, Niwa Y, Ohmiya N, Kamiya K, Sakata T, Ando N, Ito B, Sasaki Y, Hayakawa T

    GASTROINTESTINAL ENDOSCOPY   53 巻 ( 5 ) 頁: AB212 - AB212   2001年4月

  124. Diagnosis of gastrointestinal stromal tumor using endscopic ultrasonography-guided fine needle aspiration biopsy.

    Ando, N; Goto, H; Niwa, Y; Hirooka, Y; Koijima, S; Hosoi, T; Shinkai, M; Sakata, T; Otsuka, Y; Hayakawa, T

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  125. Statistical Analysis of the Horizontal Phase Velocity Distribution of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances in Airglow Images Over Sata (31.0°N, 130.7°E), Japan 査読有り

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    Journal of Geophysical Research: Space Physics   128 巻 ( 12 )   2023年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: https://doi.org/10.1029/2023JA031600

    DOI: https://doi.org/10.1029/2023JA031600

  126. Machine learning approach for ionospheric scintillation prediction on ROTI parameter over the African region during solar cycle 24 査読有り

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    Advances in Space Research     2023年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: https://doi.org/10.1016/j.asr.2023.12.026

    DOI: https://doi.org/10.1016/j.asr.2023.12.026

  127. New aspects of the upper atmospheric disturbances caused by the explosive eruption of the 2022 Hunga Tonga-Hunga Ha'apai volcano 招待有り 査読有り

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    EARTH PLANETS AND SPACE   75 巻 ( 1 ) 頁: 175   2023年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  128. Periodic oscillations of Doppler frequency excited by the traveling ionospheric disturbances associated with the Tonga eruption in 2022 査読有り

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    EARTH PLANETS AND SPACE   75 巻 ( 1 )   2023年10月

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    DOI: 10.1186/s40623-023-01914-4

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  129. Statistical Analysis of the Horizontal Phase Velocity Distribution of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances in Airglow Images Over Darwin (12.4°S, 131.0°E) 査読有り 国際共著

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    Journal of Geophysical Research: Space Physics   128 巻 ( 8 )   2023年8月

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    DOI: https://doi.org/10.1029/2022JA030769

    DOI: https://doi.org/10.1029/2022JA030769

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  130. Spatio-Temporal Characteristics of IPDP-Type EMIC Waves on April 19, 2017: Implications for Loss of Relativistic Electrons in the Outer Belt 査読有り

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  131. Generation of equatorial plasma bubble after the 2022 Tonga volcanic eruption 査読有り

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    SCIENTIFIC REPORTS   13 巻 ( 1 ) 頁: 6450   2023年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  132. Statistical analysis for EUV dynamic spectra and their impact on the ionosphere during solar flares 査読有り

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    EARTH PLANETS AND SPACE   75 巻 ( 1 )   2023年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-023-01788-6

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  133. Multi-Event Analysis of Magnetosphere-Ionosphere Coupling of Nighttime Medium-Scale Traveling Ionospheric Disturbances From the Ground and the Arase Satellite 査読有り

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 2 )   2023年2月

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  134. A Statistical Study of Longitudinal Extent of Pc1 Pulsations Using Seven PWING Ground Stations at Subauroral Latitudes 査読有り

    Liu, J; Shiokawa, K; Oyama, SI; Otsuka, Y; Jun, CW; Nose, M; Nagatsuma, T; Sakaguchi, K; Kadokura, A; Ozaki, M; Connors, M; Baishev, D; Nishitani, N; Oinats, A; Kurkin, V; Raita, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   128 巻 ( 1 )   2023年1月

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    DOI: 10.1029/2021JA029987

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  135. Generation Mechanisms of Plasma Density Irregularity in the Equatorial Ionosphere During a Geomagnetic Storm on 21-22 December 2014

    Sori, T; Shinbori, A; Otsuka, Y; Tsugawa, T; Nishioka, M; Yoshikawa, A

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   127 巻 ( 5 )   2022年5月

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  136. Propagation characteristics of sporadic E and medium-scale traveling ionospheric disturbances (MSTIDs): statistics using HF Doppler and GPS-TEC data in Japan

    Matsushima, R; Hosokawa, K; Sakai, J; Otsuka, Y; Ejiri, MK; Nishioka, M; Tsugawa, T

    EARTH PLANETS AND SPACE   74 巻 ( 1 )   2022年4月

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  137. Propagation Direction Analyses of Medium-Scale Traveling Ionospheric Disturbances Observed Over North America With GPS-TEC Perturbation Maps by Three-Dimensional Spectral Analysis Method

    Perwitasari, S; Nakamura, T; Tsugawa, T; Nishioka, M; Tomikawa, Y; Ejiri, MK; Kogure, M; Otsuka, Y; Shinbori, A; Jin, H; Tao, C

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   127 巻 ( 1 )   2022年1月

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  138. Propagation Mechanism of Medium Wave Broadcasting Waves Observed by the Arase Satellite: Hectometric Line Spectra

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 11 )   2021年11月

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    DOI: 10.1029/2021JA029813

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  139. Isolated Proton Aurora Driven by EMIC Pc1 Wave: PWING, Swarm, and NOAA POES Multi-Instrument Observations

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    GEOPHYSICAL RESEARCH LETTERS   48 巻 ( 18 )   2021年9月

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    DOI: 10.1029/2021GL095090

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  140. First Simultaneous Observation of a Night Time Medium-Scale Traveling Ionospheric Disturbance From the Ground and a Magnetospheric Satellite

    Kawai, K; Shiokawa, K; Otsuka, Y; Oyama, S; Kasaba, Y; Kasahara, Y; Tsuchiya, F; Kumamoto, A; Nakamura, S; Matsuoka, A; Imajo, S; Kazama, Y; Wang, SY; Tam, SWY; Chang, TF; Wang, BJ; Asamura, K; Kasahara, S; Yokota, S; Keika, K; Hori, T; Miyoshi, Y; Jun, C; Shoji, M; Shinohara, I

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 9 )   2021年9月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2020JA029086

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  141. Coupled investigations of ionosphere variations over European and Japanese regions: observations, comparative analysis, and validation of models and facilities

    Panasenko, SV; Kotov, DV; Otsuka, Y; Yamamoto, M; Hashiguchi, H; Richards, PG; Truhlik, V; Bogomaz, OV; Shulha, MO; Zhivolup, TG; Domnin, IF

    PROGRESS IN EARTH AND PLANETARY SCIENCE   8 巻 ( 1 )   2021年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40645-021-00441-8

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  142. Model-based reproduction and validation of the total spectra of a solar flare and their impact on the global environment at the X9.3 event of September 6, 2017

    Watanabe, K; Jin, H; Nishimoto, S; Imada, S; Kawai, T; Kawate, T; Otsuka, Y; Shinbori, A; Tsugawa, T; Nishioka, M

    EARTH PLANETS AND SPACE   73 巻 ( 1 )   2021年4月

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  143. Multi-Event Analysis of Plasma and Field Variations in Source of Stable Auroral Red (SAR) Arcs in Inner Magnetosphere During Non-Storm-Time Substorms

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 4 )   2021年4月

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    DOI: 10.1029/2020JA029081

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  144. Formation of an additional density peak in the bottom side of the sodium layer associated with the passage of multiple mesospheric frontal systems

    Narayanan, VL; Nozawa, S; Oyama, SI; Mann, I; Shiokawa, K; Otsuka, Y; Saito, N; Wada, S; Kawahara, TD; Takahashi, T

    ATMOSPHERIC CHEMISTRY AND PHYSICS   21 巻 ( 4 ) 頁: 2343 - 2361   2021年2月

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    DOI: 10.5194/acp-21-2343-2021

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  145. Comparison of seasonal and longitudinal variation of daytime MSTID activity using GPS observation and GAIA simulations

    Sivakandan, M; Otsuka, Y; Ghosh, P; Shinagawa, H; Shinbori, A; Miyoshi, Y

    EARTH PLANETS AND SPACE   73 巻 ( 1 )   2021年2月

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    DOI: 10.1186/s40623-021-01369-5

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  146. On the Generation of an Unseasonal EPB Over South East Asia

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    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 2 )   2021年2月

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  147. Solar activity dependence of medium-scale traveling ionospheric disturbances using GPS receivers in Japan

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    EARTH PLANETS AND SPACE   73 巻 ( 1 )   2021年1月

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    DOI: 10.1186/s40623-020-01353-5

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  148. Challenges to Equatorial Plasma Bubble and Ionospheric Scintillation Short-Term Forecasting and Future Aspects in East and Southeast Asia

    Li, GZ; Ning, BQ; Otsuka, Y; Abdu, MA; Abadi, P; Liu, ZZ; Spogli, L; Wan, WX

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  149. Plasma and Field Observations in the Magnetospheric Source Region of a Stable Auroral Red (SAR) Arc by the Arase Satellite on 28 March 2017

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  150. Dilatory and Downward Development of 3-m Scale Irregularities in the Funnel-Like Region of a Rapidly Rising Equatorial Plasma Bubble

    Ram, ST; Ajith, KK; Yokoyama, T; Yamamoto, M; Hozumi, K; Shiokawa, K; Otsuka, Y; Li, G

    GEOPHYSICAL RESEARCH LETTERS   47 巻 ( 13 )   2020年7月

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  151. Day-to-day variation of pre-reversal enhancement in the equatorial ionosphere based on GAIA model simulations

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    EARTH PLANETS AND SPACE   72 巻 ( 1 )   2020年7月

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    DOI: 10.1186/s40623-020-01228-9

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  152. Observations of equatorial plasma bubbles using a low-cost 630.0-nm all-sky imager in Ishigaki Island, Japan

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    EARTH PLANETS AND SPACE   72 巻 ( 1 )   2020年5月

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  153. Probability of Ionospheric Plasma Bubble Occurrence as a Function of Pre-Reversal Enhancement Deduced from Ionosondes in Southeast Asia

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    7TH INTERNATIONAL SEMINAR ON AEROSPACE SCIENCE AND TECHNOLOGY (ISAST 2019)   2226 巻   2020年

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  154. New observations of the total electron content and ionospheric scintillations over Ho Chi Minh city

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  155. Capability of Geomagnetic Storm Parameters to Identify Severe Space Weather

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  156. A Neural Network-Based Ionospheric Model Over Africa From Constellation Observing System for Meteorology, Ionosphere, and Climate and Ground Global Positioning System Observations

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  157. Investigation of Spatiotemporal Morphology of Plasma Bubbles Based on EAR Observations 査読有り

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  158. Three-Dimensional Fourier Analysis of the Phase Velocity Distributions of Mesospheric and Ionospheric Waves Based on Airglow Images Collected Over 10 Years: Comparison of Magadan, Russia, and Athabasca, Canada 査読有り

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  159. Observation and characterization of traveling ionospheric disturbances induced by solar eclipse of 20 March 2015 using incoherent scatter radars and GPS networks 査読有り

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    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   191 巻   2019年9月

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  160. Thermospheric wind variations observed by a Fabry-Perot interferometer at Tromso, Norway, at substorm onsets 査読有り

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  161. Direct Observations of Traveling Ionospheric Disturbances as Focusers of Solar Radiation: Spectral Caustics 査読有り

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  162. Response of the Ionosphere-Plasmasphere Coupling to the September 2017 Storm:What Erodes the Plasmasphere so Severley? 査読有り

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  163. Spatiotemporal development of pulsating auroral patch associated with discrete chorus elements: Arase and PWING observations 査読有り

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  164. Development of multivariate ionospheric TEC forecasting algorithm using linear time series model and ARMA over low-latitude GNSS station 査読有り

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  165. Multicomponent Analysis of Ionospheric Scintillation Effects Using the Synchrosqueezing Technique for Monitoring and Mitigating their Impact on GNSS Signals 査読有り

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  166. Daytime Periodic Wave-like Structures in the Ionosphere Observed at Low Latitudes over the Asian-Australian Sector Using Total Electron Content from Beidou Geostationary Satellites 査読有り

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  167. Observations of Low-Latitude Traveling Ionospheric Disturbances by a 630.0-nm Airglow Imager and the CHAMP Satellite Over Indonesia 査読有り

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  168. Visualization of rapid electron precipitation via chorus element wave-particle interactions 査読有り

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  169. Implementation of Hybrid Ionospheric TEC Forecasting Algorithm Using PCA-NN Method 査読有り

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  170. Rapid Loss of Relativistic Electrons by EMIC Waves in the Outer Radiation Belt Observed by Arase, Van Allen Probes, and the PWING Ground Stations 査読有り

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    DOI: 10.1029/2018GL080262

    Web of Science

    その他リンク: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2018GL080262

  171. Microscopic Observations of Pulsating Aurora Associated With Chorus Element Structures: Coordinated Arase Satellite-PWING Observations 査読有り

    Ozaki, M; Shiokawa, K; Miyoshi, Y; Hosokawa, K; Oyama, S; Yagitani, S; Kasahara, Y; Kasaba, Y; Matsuda, S; Kataoka, R; Ebihara, Y; Ogawa, Y; Otsuka, Y; Kurita, S; Moore, RC; Tanaka, YM; Nosé, M; Nagatsuma, T; Connors, M; Nishitani, N; Katoh, Y; Hikishima, M; Kumamoto, A; Tsuchiya, F; Kadokura, A; Nishiyama, T; Inoue, T; Imamura, K; Matsuoka, A; Shinohara, I

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 22 ) 頁: 12125 - 12134   2018年11月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018GL079812

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  172. Statistical Analysis of SAR Arc Detachment From the Main Oval Based on 11-Year, AII-sky Imaging Observation at Athabasca, Canada 査読有り

    Takagi, Y; Shiokawa, K; Otsuka, Y; Connors, M; Schofield, I

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 21 ) 頁: 11539 - 11546   2018年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018GL079615

    Web of Science

  173. Review of the generation mechanisms of post-midnight irregularities in the equatorial and low-latitude ionosphere 査読有り

    Otsuka, Y

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5 巻   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40645-018-0212-7

    Web of Science

  174. Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering 査読有り

    Figueiredo, CAOB; Takahashi, H; Wrasse, CM; Otsuka, Y; Shiokawa, K; Barros, D

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 9 ) 頁: 7843 - 7857   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018JA025438

    Web of Science

  175. Storm-Enhanced Development of Postsunset Equatorial Plasma Bubbles Around the Meridian 120 degrees E/60 degrees W on 7-8 September 2017 査読有り

    Li Guozhu, Ning Baiqi, Wang Chi, Abdu M. A., Otsuka Yuichi, Yamamoto M., Wu Jian, Chen Jinsong

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 9 ) 頁: 7985 - 7998   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018JA025871

    Web of Science

  176. Temporal and Spatial Variations of Storm Time Midlatitude Ionospheric Trough Based on Global GNSS-TEC and Arase Satellite Observations 査読有り

    Shinbori, A; Otsuka, Y; Tsugawa, T; Nishioka, M; Kumamoto, A; Tsuchiya, F; Matsuda, S; Kasahara, Y; Matsuoka, A; Ruohoniemi, JM; Shepherd, SG; Nishitani, N

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 15 ) 頁: 7362 - 7370   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018GL078723

    Web of Science

  177. On the Role of Thermospheric Winds and Sporadic E Layers in the Formation and Evolution of Electrified MSTIDs in Geomagnetic Conjugate Regions 査読有り

    Narayanan V. L., Shiokawa K., Otsuka Y., Neudegg D.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 8 ) 頁: 6957 - 6980   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018JA025261

    Web of Science

  178. On the Solstice Maxima and Azimuth-Dependent Characteristics of the 150-km Echoes Observed Using the Equatorial Atmosphere Radar 査読有り

    Chaitanya, PP; Patra, AK; Otsuka, Y; Yokoyama, T; Yamamoto, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 8 ) 頁: 6752 - 6759   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018JA025491

    Web of Science

  179. Statistical Analysis of the Phase Velocity Distribution of Mesospheric and Ionospheric Waves Observed in Airglow Images Over a 16-Year Period: Comparison Between Rikubetsu and Shigaraki, Japan 査読有り

    Tsuchiya, S; Shiokawa, K; Fujinami, H; Otsuka, Y; Nakamura, T; Yamamoto, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 8 ) 頁: 6930 - 6947   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018JA025585

    Web of Science

  180. Quantum criticality in the metal-superconductor transition of interacting Dirac fermions on a triangular lattice 査読有り

    Otsuka Yuichi, Seki Kazuhiro, Sorella Sandro, Yunoki Seiji

    PHYSICAL REVIEW B   98 巻 ( 3 )   2018年7月

  181. Equatorial plasma bubble seeding by MSTIDs in the ionosphere 査読有り

    Takahashi, H; Wrasse, CM; Figueiredo, CAOB; Barros, D; Abdu, MA; Otsuka, Y; Shiokawa, K

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5 巻 ( 1 )   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40645-018-0189-2

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  182. Total Electron Content Observations by Dense Regional and Worldwide International Networks of GNSS

    Tsugawa Takuya, Nishioka Michi, Ishii Mamoru, Hozumi Kornyanat, Saito Susumu, Shinbori Atsuki, Otsuka Yuichi, Saito Akinori, Buhari Suhaila M., Abdullah Mardina, Supnithi Pornchai

    JOURNAL OF DISASTER RESEARCH   13 巻 ( 3 ) 頁: 535-545   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  183. Total Electron Content Observations by Dense Regional and Worldwide International Networks of GNSS 査読有り

    Tsugawa Takuya, Nishioka Michi, Ishii Mamoru, Hozumi Kornyanat, Saito Susumu, Shinbori Atsuki, Otsuka Yuichi, Saito Akinori, Buhari Suhaila M, Abdullah Mardina, Supnithi Pornchai

    JOURNAL OF DISASTER RESEARCH   13 巻 ( 3 ) 頁: 535 - 545   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.20965/jdr.2018.p0535

    Web of Science

  184. Relationship between day-to-day variability of equatorial plasma bubble activity from GPS scintillation and atmospheric properties from Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) assimilation 査読有り

    Yamamoto, M; Otsuka, Y; Jin, H; Miyoshi, Y

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5 巻   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40645-018-0184-7

    Web of Science

  185. Spatial and temporal characteristics of ionospheric total electron content over Indian equatorial and low-latitude GNSS stations 査読有り

    G. Sivavaraprasad, Yuichi Otsuka, Nitin Kumar Tripathi, V Rajesh Chowdhary, D Venkata Ratnam, Mohammed Afzal Khan

    2018 Conference on Signal Processing And Communication Engineering Systems, SPACES 2018   2018- 巻   頁: 105 - 108   2018年3月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Electrical and Electronics Engineers Inc.  

    The study and understanding of the intermittent characteristics of equatorial and low latitude ionosphere is crucial for modelling and forecasting the ionosphere and space weather conditions. The performance of space-based navigation systems such as Global Positioning System (GPS) is affected by the sporadic temporal and spatial variations of ionospheric Total Electron Content (TEC). The variability of ionospheric electron density over Indian low latitude sector is difficult to model due to Equatorial Ionization Anomaly (EIA). In this paper, Multi-fractal aspects of the GPS measured TEC is investigated during both high and low solar activity periods of 24th solar cycle. The vertical TEC (VTEC) data sets are obtained from two Indian low latitude stations namely, Bangalore (Geographical Latitude: 13.020 N, Geographical Longitude: 77.57o E), and Lucknow (Geographical Latitude: 26.830 N, Geographical Longitude: 80.92o E) for two year long period 2013 and 2015. The experimental results shows that the respective geographic sites have important scaling differences as well as similarities when their Multi-fractal signatures for VTEC are compared. These differences and similarities are interpreted in terms of the EIA conditions, where this phenomenon is an important source of intermittence due to the presence of the VTEC peaks at ±300 geomagnetic latitudes. During the high solar activity period, the intermittence characteristics of VTEC over EIA region (Lucknow) are relatively more complex than equatorial (Bengaluru) station, whereas during low solar activity period the scenario is reciprocal.

    DOI: 10.1109/SPACES.2018.8316326

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  186. Daily and seasonal variations in the linear growth rate of the Rayleigh-Taylor instability in the ionosphere obtained with GAIA 査読有り

    Shinagawa, H; Jin, H; Miyoshi, Y; Fujiwara, H; Yokoyama, T; Otsuka, Y

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5 巻   2018年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40645-018-0175-8

    Web of Science

  187. Medium-Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil 査読有り

    Figueiredo, CAOB; Takahashi, H; Wrasse, CM; Otsuka, Y; Shiokawa, K; Barros, D

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 3 ) 頁: 2215 - 2227   2018年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA025021

    Web of Science

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  188. Daytime F-region irregularity triggered by rocket-induced ionospheric hole over low latitude 査読有り

    Li, GZ; Ning, BQ; Abdu, MA; Wang, C; Otsuka, Y; Wan, WX; Lei, JH; Nishioka, M; Tsugawa, T; Hu, LH; Yang, GT; Yan, CX

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5 巻 ( 1 )   2018年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40645-018-0172-y

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  189. Discovery of 1Hz Range Modulation of Isolated Proton Aurora at Subauroral Latitudes 査読有り

    Ozaki, M; Shiokawa, K; Miyoshi, Y; Kataoka, R; Connors, M; Inoue, T; Yagitani, S; Ebihara, Y; Jun, CW; Nomura, R; Sakaguchi, K; Otsuka, Y; Uchida, HA; Schofield, I; Danskin, DW

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 3 ) 頁: 1209 - 1217   2018年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017GL076486

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  190. Observations of Ultrawideband Signals in GPS TEC Variations over Europe during Solar Eclipse 査読有り

    Panasenko Sergii V, Chernogor Leonid F, Lazorenko Oleg V, Otsuka Yuichi, van de Kamp Max

    2018 9TH INTERNATIONAL CONFERENCE ON ULTRAWIDEBAND AND ULTRASHORT IMPULSE SIGNALS (UWBUSIS)     頁: 115 - 118   2018年

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  191. Temporal and spatial variations of mid-latitude ionospheric trough during a geomagnetic storm based on global GNSS-TEC and Arase satellite observations 査読有り

    2018 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC)     2018年

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  192. First Study on the Occurrence Frequency of Equatorial Plasma Bubbles over West Africa Using an All-Sky Airglow Imager and GNSS Receivers 査読有り

    Okoh, D; Rabiu, B; Shiokawa, K; Otsuka, Y; Segun, B; Falayi, E; Onwuneme, S; Kaka, R

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 12 ) 頁: 12430 - 12444   2017年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA024602

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  193. Ground-based instruments of the PWING project to investigate dynamics of the inner magnetosphere at subauroral latitudes as a part of the ERG-ground coordinated observation network 査読有り

    Shiokawa, K; Katoh, Y; Hamaguchi, Y; Yamamoto, Y; Adachi, T; Ozaki, M; Oyama, SI; Nosé, M; Nagatsuma, T; Tanaka, Y; Otsuka, Y; Miyoshi, Y; Kataoka, R; Takagi, Y; Takeshita, Y; Shinbori, A; Kurita, S; Hori, T; Nishitani, N; Shinohara, I; Tsuchiya, F; Obana, Y; Suzuki, S; Takahashi, N; Seki, K; Kadokura, A; Hosokawa, K; Ogawa, Y; Connors, M; Ruohoniemi, JM; Engebretson, M; Turunen, E; Ulich, T; Manninen, J; Raita, T; Kero, A; Oksanen, A; Back, M; Kauristie, K; Mattanen, J; Baishev, D; Kurkin, V; Oinats, A; Pashinin, A; Vasilyev, R; Rakhmatulin, R; Bristow, W; Karjala, M

    EARTH PLANETS AND SPACE   69 巻   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-017-0745-9

    Web of Science

  194. The Solar Flux Dependence of Ionospheric 150 km Radar Echoes and Implications 査読有り

    Patra, AK; Chaitanya, PP; St-Maurice, JP; Otsuka, Y; Yokoyama, T; Yamamoto, M

    GEOPHYSICAL RESEARCH LETTERS   44 巻 ( 22 ) 頁: 11257 - 11264   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017GL074678

    Web of Science

  195. On the effect of thermospheric neutral winds on post-midnight field-aligned irregularities at low latitudes 査読有り

    Tam Dao, Yuichi Otsuka, Kazuo Shiokawa, Michi Nishioka, Mamoru Yamamoto, Suhaila M. Buhari, Mardina Abdullah, Asnawi Husin

    2017 32nd General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2017   2017- 巻   頁: 1 - 4   2017年11月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Electrical and Electronics Engineers Inc.  

    We investigated a post-midnight Field-Aligned Irregularities (FAIs) event observed with the Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S, 100.3°E, dip lat. 10.4°S) in Indonesia on the night of 9 July 2010, using a comprehensive dataset of both neutral and plasma parameters. We compared FAI echoes collocated with 630 nm airglow depletion detected by an all-sky imager. The thermospheric neutral winds and temperatures obtained by a Fabry-Perot interferometer at Kototabang and the altitudes of F-layer (h'F) observed with ionosondes at Kototabang, Chiang Mai, and Chumphon were also examined. We found that the 3-m scale post-midnight FAIs occurred within plasma bubbles. The convergence of the equatorward neutral winds happened in this particular event related to midnight temperature maximum (MTM) and that the equatorward winds in both northern and southern hemispheres could be responsible for the growth of plasma bubbles around midnight. The uplift of F-layer at low latitudes could increase the growth rate of the Rayleigh-Taylor instability. Eastward electric currents driven by the equatorward winds could also contribute to the generation of the irregularities at post-midnight.

    DOI: 10.23919/URSIGASS.2017.8105106

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  196. Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied by a midnight brightness wave at low latitudes (vol 69, 112, 2017) 査読有り

    Fukushima, D; Shiokawa, K; Otsuka, Y; Kubota, M; Yokoyama, T; Nishioka, M; Komonjinda, S; Yatini, CY

    EARTH PLANETS AND SPACE   69 巻   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-017-0729-9

    Web of Science

  197. Characteristics of Seasonal Variation and Solar Activity Dependence of the Geomagnetic Solar Quiet Daily Variation 査読有り

    Shinbori, A; Koyama, Y; Nosé, M; Hori, T; Otsuka, Y

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 10 ) 頁: 10796 - 10810   2017年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA024342

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  198. Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied by a midnight brightness wave at low latitudes 査読有り

    Fukushima, D; Shiokawa, K; Otsuka, Y; Kubota, M; Yokoyama, T; Nishioka, M; Komonjinda, S; Yatini, CY

    EARTH PLANETS AND SPACE   69 巻   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-017-0698-z

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  199. Daytime zonal drifts in the ionospheric 150km and E regions estimated using EAR observations 査読有り

    Pavan Chaitanya P., Patra A. K., Otsuka Y., Yokoyama T., Yamamoto M., Stoneback R. A., Heelis R. A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 8 ) 頁: 9045 - 9055   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA024589

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  200. Sixteen year variation of horizontal phase velocity and propagation direction of mesospheric and thermospheric waves in airglow images at Shigaraki, Japan 査読有り

    Takeo, D; Shiokawa, K; Fujinami, H; Otsuka, Y; Matsuda, TS; Ejiri, MK; Nakamura, T; Yamamoto, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 8 ) 頁: 8770 - 8780   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA023919

    Web of Science

  201. Equinoctial asymmetry in the zonal distribution of scintillation as observed by GPS receivers in Indonesia 査読有り

    Abadi, P; Otsuka, Y; Shiokawa, K; Husin, A; Liu, HX; Saito, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 8 ) 頁: 8947 - 8958   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA024146

    Web of Science

  202. Sixteen-year variation of horizontal phase velocity and propagation direction of mesospheric and thermospheric waves in airglow images at Shigaraki 査読有り

    Takeo, D, K. Shiokawa, H. Fujinami, Y. Otsuka, T. S. Matsuda, M. K. Ejiri, T. Nakamura, M. Yamamoto

    Journal of Geophysical Research -Atmospheres   122 巻   頁: 8770-8780   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We analyzed the horizontal phase velocity of gravity waves and medium-scale traveling ionospheric disturbances (MSTIDs) by using the three-dimensional fast Fourier transform method developed by Matsuda et al. (2014) for 557.7 nm (altitude: 90–100 km) and 630.0 nm (altitude: 200–300 km) airglow images obtained at Shigaraki MU Observatory (34.8°N, 136.1°E, dip angle: 49°) over ∼16 years from 16 March 1999 to 20 February 2015. The analysis of 557.7 nm airglow images shows clear seasonal variation of the propagation direction of gravity waves in the mesopause region. In spring, summer, fall, and winter, the peak directions are northeastward, northeastward, northwestward, and southwestward, respectively. The difference in east-west propagation direction between summer and winter is probably caused by the wind filtering effect due to the zonal mesospheric jet. Comparison with tropospheric reanalysis data shows that the difference in north-south propagation direction between summer and winter is caused by differences in the latitudinal location of wave sources due to convective activity in the troposphere relative to Shigaraki. The analysis of 630.0 nm airglow images shows that t

    DOI: 10.0002/2017JA023919

  203. Coordinated observations of postmidnight irregularities and thermospheric neutral winds and temperatures at low latitudes 査読有り

    Dao, T; Otsuka, Y; Shiokawa, K; Nishioka, M; Yamamoto, M; Buhari, SM; Abdullah, M; Husin, A

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 7 ) 頁: 7504 - 7518   2017年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2017JA024048

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  204. Detection of Plasma Bubble in Ionosphere using GPS Receivers in Southeast Asia 査読有り

    Buhari, SM; Abdullah, M; Otsuka, Y; Yokoyama, T; Nishioka, M; Hasbi, AM; Tsugawa, T

    SAINS MALAYSIANA   46 巻 ( 6 ) 頁: 879 - 885   2017年6月

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    記述言語:マレー語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.17576/jsm-2017-4606-06

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  205. Measurement of thermospheric temperatures using OMTI Fabry-Perot interferometers with 70-mm etalon 査読有り

    Nakamura, Y; Shiokawa, K; Otsuka, Y; Oyama, S; Nozawa, S; Komolmis, T; Komonjida, S; Neudegg, D; Yuile, C; Meriwether, J; Shinagawa, H; Jin, H

    EARTH PLANETS AND SPACE   69 巻   2017年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-017-0643-1

    Web of Science

  206. Large-scale traveling ionospheric disturbances observed by GPS dTEC maps over North and South America on Saint Patrick's Day storm in 2015 査読有り

    Figueiredo, CAOB; Wrasse, CM; Takahashi, H; Otsuka, Y; Shiokawa, K; Barros, D

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 4 ) 頁: 4755 - 4763   2017年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016JA023417

    Web of Science

  207. Climatology of successive equatorial plasma bubbles observed by GPS ROTI over Malaysia 査読有り

    Buhari, SM; Abdullah, M; Yokoyama, T; Otsuka, Y; Nishioka, M; Hasbi, AM; Bahari, SA; Tsugawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   122 巻 ( 2 ) 頁: 2174 - 2184   2017年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016JA023202

    Web of Science

  208. STATISTICAL ANALYSIS OF THE OCCURRENCES OF MSTIDs OBSERVED BY ALL-SKY IMAGER IN LOW MAGNETIC LATITUDE 査読有り

    2017 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS)     頁: 4425 - 4428   2017年

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  209. The first long-term all-sky imager observation of lunar sodium tail 査読有り

    Nishino, MN; Shiokawa, K; Otsuka, Y

    ICARUS   280 巻   頁: 199 - 204   2016年12月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.icarus.2016.08.004

    Web of Science

  210. Three years of concentric gravity wave variability in the mesopause as observed by IMAP/VISI 査読有り

    Perwitasari, S; Sakanoi, T; Nakamura, T; Ejiri, MK; Tsutsumi, M; Tomikawa, Y; Otsuka, Y; Yamazaki, A; Saito, A

    GEOPHYSICAL RESEARCH LETTERS   43 巻 ( 22 ) 頁: 11528 - 11535   2016年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016GL071511

    Web of Science

  211. Ionospheric TEC Weather Map Over South America 査読有り

    Takahashi, H; Wrasse, CM; Denardini, CM; Pádua, MB; de Paula, ER; Costa, SMA; Otsuka, Y; Shiokawa, K; Monico, JFG; Ivo, A; Sant'Anna, N

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   14 巻 ( 11 ) 頁: 937 - 949   2016年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016SW001474

    Web of Science

  212. On the fresh development of equatorial plasma bubbles around the midnight hours of June solstice 査読有り

    Ajith, KK; Ram, ST; Yamamoto, M; Otsuka, Y; Niranjan, K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 9 ) 頁: 9051 - 9062   2016年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016JA023024

    Web of Science

  213. Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes 査読有り

    Ozaki, M; Shiokawa, K; Miyoshi, Y; Kataoka, R; Yagitani, S; Inoue, T; Ebihara, Y; Jun, CW; Nomura, R; Sakaguchi, K; Otsuka, Y; Shoji, M; Schofield, I; Connors, M; Jordanova, VK

    GEOPHYSICAL RESEARCH LETTERS   43 巻 ( 15 ) 頁: 7859 - 7866   2016年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016GL070008

    Web of Science

  214. Enhanced ionospheric plasma bubble generation in more active ITCZ 査読有り

    Li, GZ; Otsuka, Y; Ning, BQ; Abdu, MA; Yamamoto, M; Wan, WX; Liu, LB; Abadi, P

    GEOPHYSICAL RESEARCH LETTERS   43 巻 ( 6 ) 頁: 2389 - 2395   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016GL068145

    Web of Science

  215. Altitude development of postmidnight F region field-aligned irregularities observed using Equatorial Atmosphere Radar in Indonesia 査読有り

    Tam Dao, Otsuka Yuichi, Shiokawa Kazuo, Ram S. Tulasi, Yamamoto Mamoru

    GEOPHYSICAL RESEARCH LETTERS   43 巻 ( 3 ) 頁: 1015 - 1022   2016年2月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015GL067432

    Web of Science

  216. Pulsating proton aurora caused by rising tone Pc1 waves 査読有り

    Nomura, R; Shiokawa, K; Omura, Y; Ebihara, Y; Miyoshi, Y; Sakaguchi, K; Otsuka, Y; Connors, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 2 ) 頁: 1608 - 1618   2016年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021681

    Web of Science

  217. Duskside enhancement of equatorial zonal electric field response to convection electric fields during the St. Patrick's Day storm on 17 March 2015 査読有り

    Ram, ST; Yokoyama, T; Otsuka, Y; Shiokawa, K; Sripathi, S; Veenadhari, B; Heelis, R; Ajith, KK; Gowtam, VS; Gurubaran, S; Supnithi, P; Le Huy, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 1 ) 頁: 538 - 548   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021932

    Web of Science

  218. ISS-IMAPによる大気光波状構造の観測

    齊藤昭則, 穂積裕太, 坂野井健, S. Perwitasari, 吉川一朗, 山崎敦, 大塚雄一, 山本衛

    第29回大気圏シンポジウム: 講演集録     2016年

  219. TEC variation during high and low solar activities over South American sector 査読有り

    Jonah, OF; de Paula, ER; Muella, MTAH; Dutra, SLG; Kherani, EA; Negreti, PMS; Otsuka, Y

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   135 巻   頁: 22 - 35   2015年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2015.10.005

    Web of Science

  220. A direct link between chorus emissions and pulsating aurora on timescales from milliseconds to minutes: A case study at subauroral latitudes 査読有り

    Ozaki, M; Yagitani, S; Sawai, K; Shiokawa, K; Miyoshi, Y; Kataoka, R; Ieda, A; Ebihara, Y; Connors, M; Schofield, I; Katoh, Y; Otsuka, Y; Sunagawa, N; Jordanova, VK

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 11 ) 頁: 9617 - 9631   2015年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021381

    Web of Science

  221. Coordinated airglow observations between IMAP/VISI and a ground-based all-sky imager on concentric gravity wave in the mesopause 査読有り

    Perwitasari, S; Sakanoi, T; Yamazaki, A; Otsuka, Y; Hozumi, Y; Akiya, Y; Saito, A; Shiokawa, K; Kawamura, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 11 ) 頁: 9706 - 9721   2015年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021424

    Web of Science

  222. Multi-instrument, high-resolution imaging of polar cap patch transportation 査読有り

    Thomas, EG; Hosokawa, K; Sakai, J; Baker, JBH; Ruohoniemi, JM; Taguchi, S; Shiokawa, K; Otsuka, Y; Coster, AJ; St-Maurice, JP; McWilliams, KA

    RADIO SCIENCE   50 巻 ( 9 ) 頁: 904 - 915   2015年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015RS005672

    Web of Science

  223. Plasma bubble monitoring by TEC map and 630 nm airglow image 査読有り

    Takahashi, H; Wrasse, CM; Otsuka, Y; Ivo, A; Gomes, V; Paulino, I; Medeiros, AF; Denardini, CM; Sant'Anna, N; Shiokawa, K

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   130 巻   頁: 151 - 158   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2015.06.003

    Web of Science

  224. Statistical study of auroral fragmentation into patches 査読有り

    Hashimoto, A; Shiokawa, K; Otsuka, Y; Oyama, S; Nozawa, S; Hori, T; Lester, M; Johnsen, MG

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 8 ) 頁: 6207 - 6217   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021000

    Web of Science

  225. Fresh and evolutionary-type field-aligned irregularities generated near sunrise terminator due to overshielding electric fields 査読有り

    Ram, ST; Ajith, KK; Yamamoto, M; Otsuka, Y; Yokoyama, T; Niranjan, K; Gurubaran, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 7 ) 頁: 5922 - 5930   2015年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021427

    Web of Science

  226. Effects of pre-reversal enhancement of E x B drift on the latitudinal extension of plasma bubble in Southeast Asia 査読有り

    Abadi, P; Otsuka, Y; Tsugawa, T

    EARTH PLANETS AND SPACE   67 巻   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-015-0246-7

    Web of Science

  227. Airglow-imaging observation of plasma bubble disappearance at geomagnetically conjugate points 査読有り

    Shiokawa, K; Otsuka, Y; Lynn, KJW; Wilkinson, P; Tsugawa, T

    EARTH PLANETS AND SPACE   67 巻   頁: 1 - 12   2015年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-015-0202-6

    Web of Science

  228. Geomagnetically conjugate observation of plasma bubbles and thermospheric neutral winds at low latitudes 査読有り

    Fukushima, D; Shiokawa, K; Otsuka, Y; Nishioka, M; Kubota, M; Tsugawa, T; Nagatsuma, T; Komonjinda, S; Yatini, CY

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 3 ) 頁: 2222 - 2231   2015年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020398

    Web of Science

  229. Explicit characteristics of evolutionary-type plasma bubbles observed from Equatorial Atmosphere Radar during the low to moderate solar activity years 2010-2012 査読有り

    Ajith, KK; Ram, ST; Yamamoto, M; Yokoyama, T; Gowtam, VS; Otsuka, Y; Tsugawa, T; Niranjan, K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 2 ) 頁: 1371 - 1382   2015年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020878

    Web of Science

  230. CDF data archive and integrated data analysis platform for ERG-related ground data developed by ERG Science Center (ERG-SC) 査読有り

    Hori, T, Y. Miyashita, Y. Miyoshi, K. Seki, T. Segawa, Y.-M. Tanaka, K. Keika, M. Shoji, I. Shinohara, K. Shiokawa, Y. Otsuka, S. Abe, A. Yoshikawa, K. Yumoto, Y. Obana, N. Nishitani, A. S. Yukimatu, T. Nagatsuma, M. Kunitake, K. Hosokawa, Y. Ogawa, K. T. Murata, M. Nosé, H. Kawano, T. Sakanoi

    宇宙科学情報解析論文誌   JAXA-RR-14-009 巻   頁: 75 - 90   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  231. Climatology of Equatorial Plasma Bubble Observed by MyRTKnet over the Years 2008-2013 査読有り

    S. M. Buhari, M. Abdullah, T. Yokoyama, A. M. Hasbi, Y. Otsuka, M. Nishioka, S. A. Bahari, T. Tsugawa

    2015 INTERNATIONAL CONFERENCE ON SPACE SCIENCE AND COMMUNICATION (ICONSPACE)     頁: 101 - 105   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Malaysia Real-Time Kinematics GNSS Network (MyRTKnet) which consists of 78 GPS receivers was used to investigate the occurrence of equatorial plasma bubble (EPB) along 96 degrees E - 120 degrees E longitude. In this study, we present the monthly occurrence rate of EPB along the geographical longitudes of 96 degrees E - 120 degrees E for a half of solar cycle period (2008 - 2013). A 2D map of rate of TEC change index (ROTI) projected at 300 km altitude was derived from the signal paths between GPS satellites and the receivers. A ROTI keogram for one day period was obtained from the east-west cross section of the 2D ROTI maps at 4 degrees N for every 5 min. The occurrence day of EPB was determined from the keogram by the existence of ROTI larger than 0.1 TECU/min within the 96 degrees E - 120 degrees E longitude. The results show that the occurrence of EPB along the 96 degrees E - 120 degrees E has maximum during equinoctial months and is consistent with previous studies. The occurrence rate of EPB during equinoctial months shows similar characteristics in low and high solar activity due to the broad observational coverage of the MyRTKnet. In contrast, the occurrence rate of EPB during solstice months shows significant relation with solar activity. Solstice months recorded high occurrence rate of EPB in high solar activity that might be attributed to post-midnight irregularities.

    DOI: 10.1109/IconSpace.2015.7283752

    Web of Science

  232. Direct observations of blob deformation during a substorm 査読有り

    T. Ishida, Y. Ogawa, A. Kadokura, K. Hosokawa, Y. Otsuka

    ANNALES GEOPHYSICAE   33 巻 ( 5 ) 頁: 525 - 530   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:COPERNICUS GESELLSCHAFT MBH  

    Ionospheric blobs are localized plasma density enhancements, which are mainly produced by the transportation process of plasma. To understand the deformation process of a blob, observations of plasma parameters with good spatial-temporal resolution are desirable. Thus, we conducted the European Incoherent Scatter radar observations with high-speed meridional scans (60-80 s) during October and December 2013, and observed the temporal evolution of a blob during a substorm on 4 December 2013. This paper is the first report of direct observations of blob deformation during a substorm. The blob deformation arose from an enhanced plasma flow shear during the substorm expansion phase, and then the blob split into two smaller-scale blobs, whose scale sizes were more than similar to 100 km in latitude. Our analysis indicates that the Kelvin-Helmholtz instability and dissociative recombination could have deformed the blob structure.

    DOI: 10.5194/angeocom-33-525-2015

    Web of Science

  233. GAST-D flight experiment results with disturbed and quiet ionospheric conditions 査読有り

    Susumu Saito, Takayuki Yoshihara, Atsushi Kezuka, Shinji Saitoh, Sonosuke Fukushima, Yuichi Otsuka

    PROCEEDINGS OF THE 28TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS+ 2015)     頁: 1494 - 1499   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:INST NAVIGATION  

    GAST-D ground prototype and and GAST-D airborne experimental subsystem have been developed. The GAST-D ground prototype was installed at New Ishigaki Airport located in the low magnetic latitude region. With the ground prototype and the airborne experimental system, GAST-D flight experiments in the low magnetic latitude region under ionospheric quiet and disturbed conditions for the first time in the world.
    Two flight campaigns were conducted in March and September 2014. In the campaign carried out in September 2014, the vertical error performances were comparable between ionospheric quiet and disturbed condition. However, availability degradation during the severely disturbed condition is an issue. The DSIGMA monitor which is one of the airborne integrity monitors was confirmed by all-sky airglow measurements to react ionospheric disturbance.
    The next steps of the study include parameter tuning of the ground prototype and airborne experimental system to enhance service availability during ionospheric disturbed conditions.

    Web of Science

  234. Long-term variation in the upper atmosphere as seen in the geomagnetic solar quiet daily variation 査読有り

    Shinbori, A; Koyama, Y; Nose, M; Hori, T; Otsuka, Y; Yatagai, A

    EARTH PLANETS AND SPACE   66 巻   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-014-0155-1

    Web of Science

  235. CME front and severe space weather 査読有り

    Balan, N; Skoug, R; Ram, ST; Rajesh, PK; Shiokawa, K; Otsuka, Y; Batista, IS; Ebihara, Y; Nakamura, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 12 )   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020151

    Web of Science

  236. Continuous generation and two-dimensional structure of equatorial plasma bubbles observed by high-density GPS receivers in Southeast Asia 査読有り

    Buhari, SM; Abdullah, M; Hasbi, AM; Otsuka, Y; Yokoyama, T; Nishioka, M; Tsugawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 12 )   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020433

    Web of Science

  237. Airglow observations of nighttime medium-scale traveling ionospheric disturbances from Yonaguni: Statistical characteristics and low-latitude limit 査読有り

    Narayanan, VL; Shiokawa, K; Otsuka, Y; Saito, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 11 ) 頁: 9268 - 9282   2014年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020368

    Web of Science

  238. First spaceborne observation of the entire concentric airglow structure caused by tropospheric disturbance 査読有り

    Akiya, Y; Saito, A; Sakanoi, T; Hozumi, Y; Yamazaki, A; Otsuka, Y; Nishioka, M; Tsugawa, T

    GEOPHYSICAL RESEARCH LETTERS   41 巻 ( 19 ) 頁: 6943 - 6948   2014年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014GL061403

    Web of Science

  239. Auroral fragmentation into patches 査読有り

    Shiokawa, K; Hashimoto, A; Hori, T; Sakaguchi, K; Ogawa, Y; Donovan, E; Spanswick, E; Connors, M; Otsuka, Y; Oyama, SI; Nozawa, S; McWilliams, K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 10 ) 頁: 8249 - 8261   2014年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020050

    Web of Science

  240. Diagnostics of equatorial and low latitude ionosphere by TEC mapping over Brazil 査読有り

    Takahashi, H; Costa, S; Otsuka, Y; Shiokawa, K; Monico, JFG; Paula, E; Nogueira, P; Denardini, CM; Becker-Guedes, F; Wrasse, CM; Ivo, AS; Gomes, VCF; Gargarela, W; Sant'Anna, N; Gatto, R

    ADVANCES IN SPACE RESEARCH   54 巻 ( 3 ) 頁: 385 - 394   2014年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.asr.2014.01.032

    Web of Science

  241. Observations of GPS scintillation during an isolated auroral substorm 査読有り

    Hosokawa, K, Y. Otsuka, Y. Ogawa, T. Tsugawa

    Progress in Earth and Planetary Sciencs   96693290710.1186/2197-4284-1-1 巻   2014年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  242. Vertical ExB drifts from radar and C/NOFS observations in the Indian and Indonesian sectors: Consistency of observations and model 査読有り

    A. K. Patra, P. Pavan Chaitanya, Y. Otsuka, T. Yokoyama, M. Yamamoto, R. A. Stoneback, R. A. Heelis

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 5 ) 頁: 3777 - 3788   2014年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    In this paper, we analyze vertical ExB drifts obtained from the Doppler shifts of the daytime 150km radar echoes from two radar stations located off the magnetic equator, namely, Gadanki in India and Kototabang in Indonesia, and compare those with corresponding Coupled Ion Neutral Dynamics Investigation (CINDI) observations onboard the C/NOFS satellite and the Scherliess-Fejer model in an effort to understand to what extent the low-latitude vertical ExB drifts of the 150km region represent the F region vertical ExB drifts. The radar observations were made during 9-16 LT in January, June, July, and December 2009. A detailed comparison reveals that vertical ExB drifts observed by the radars at both locations agree well with those of CINDI and differ remarkably from those of the model. Importantly, the model and observed drifts show large disagreement when the observed drifts are either large or downward. Further, while the CINDI as well as the radar observations from the two longitudes are found to agree with each other on the average, they differ remarkably on several occasions when compared on a one-to-one basis. The observed difference in detail is due to measurements made in different volumes linked with latitudinal and/or longitudinal differences and underlines the role of neutral dynamics linked with tides and gravity waves in the two longitude sectors on the respective vertical ExB drifts. The results presented here are the first of their kind and are expected to have wider applications in furthering our understanding on fine-scale longitudinal variabilities in the ionosphere in general and ionospheric electrodynamics in the Indian and Indonesian sectors in particular.

    DOI: 10.1002/2013JA019732

    Web of Science

  243. Global imaging of polar cap patches with dual airglow imagers 査読有り

    Hosokawa, K; Taguchi, S; Shiokawa, K; Otsuka, Y; Ogawa, Y; Nicolls, M

    GEOPHYSICAL RESEARCH LETTERS   41 巻 ( 1 ) 頁: 1 - 6   2014年1月

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    記述言語:英語  

    DOI: 10.1002/2013GL058748

    Web of Science

  244. 赤道大気レーダーを用いた高度150km沿磁力線不規則構造のドリフト速度に関する研究 査読有り

    大塚雄一, 水谷徳仁, 塩川和夫, Amit Patra, 横山竜宏, 山本衛

    南極資料     頁: 印刷中   2014年

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)  

  245. The observation of equatorial plasma bubble using all sky imager and GPS TEC measurement 査読有り

    Suhaila M. Buhari, Mardina Abdullah, Alina Marie Hasbi, Yuichi Otsuka, Siti Aminah Bahari, Mohd Hezri Mokhtar, Michi Nishioka, Takuya Tsugawa

    2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS)     2014年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    In this study, the two-dimensional horizontal structure of EPB was observed using GPS total electron content (TEC) measurement in South East Asia region. Rate of TEC index (ROTI) is calculated from GPS TEC measurement and plotted onto two-dimensional map in geographic coordinate. Depletion of The OI 630.0 nm emission is completely coincided with ROTI enhancement region from GPS TEC measurement. Therefore, the observation using GPS TEC measurement is able to provide spatial and temporal properties of EPB in SEA region.

    Web of Science

  246. 国際宇宙ステーションからの超高層大気撮像観測ミッションISS-IMAPの現状

    齊藤 昭則, 秋谷祐亮, 穂積裕太, 山崎 敦, 阿部 琢美, 鈴木 睦, 村上豪, 坂野井 健, 吉川 一朗, 大塚 雄一, 藤原 均, 田口 真, 山本 衛, 中村 卓司, 江尻 省, 菊池 雅行, 河野 英昭, Huixin Liu, 石井 守, 久保田 実, 津川 卓也, 星野尾 一明, 坂野井 和代, IMAPワーキンググループ

    第14回宇宙科学シンポジウム 講演集     2014年

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  247. 国際宇宙ステーションからの大気光観測による赤道域電離圏擾乱の研究

    山田貴宣, 大塚雄一, 坂野井健, 山崎敦, 齊藤昭則, 秋谷祐亮

    第28回大気圏シンポジウム講演集     2014年

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  248. Vertical ExB drifts from radar and C/NOFS observations in the Indian and Indonesian sectors: Consistency of observations and model 査読有り

    A. K. Patra, P. Pavan Chaitanya, Y. Otsuka, T. Yokoyama, M. Yamamoto, R. A. Stoneback, R. A. Heelis

    Journal of Geophysical Research: Space Physics   119 巻 ( 5 ) 頁: 3777 - 3788   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    In this paper, we analyze vertical ExB drifts obtained from the Doppler shifts of the daytime 150 km radar echoes from two radar stations located off the magnetic equator, namely, Gadanki in India and Kototabang in Indonesia, and compare those with corresponding Coupled Ion Neutral Dynamics Investigation (CINDI) observations onboard the C/NOFS satellite and the Scherliess-Fejer model in an effort to understand to what extent the low-latitude vertical ExB drifts of the 150 km region represent the F region vertical ExB drifts. The radar observations were made during 9-16 LT in January, June, July, and December 2009. A detailed comparison reveals that vertical ExB drifts observed by the radars at both locations agree well with those of CINDI and differ remarkably from those of the model. Importantly, the model and observed drifts show large disagreement when the observed drifts are either large or downward. Further, while the CINDI as well as the radar observations from the two longitudes are found to agree with each other on the average, they differ remarkably on several occasions when compared on a one-to-one basis. The observed difference in detail is due to measurements made in different volumes linked with latitudinal and/or longitudinal differences and underlines the role of neutral dynamics linked with tides and gravity waves in the two longitude sectors on the respective vertical ExB drifts. The results presented here are the first of their kind and are expected to have wider applications in furthering our understanding on fine-scale longitudinal variabilities in the ionosphere in general and ionospheric electrodynamics in the Indian and Indonesian sectors in particular. Key Points First comparison of 150 km echo and C/NOFS ExB drifts over India and Indonesia These observations agree at both locations and show some longitudinal difference Radar and C/NOFS observations differ remarkably from model ©2014. American Geophysical Union. All Rights Reserved.

    DOI: 10.1002/2013JA019732

    Scopus

  249. Two-dimensional structure of equatorial plasma bubble observed using GPS networks in South East Asia region 査読有り

    Suhaila M. Buhari, Mardina Abdullah, Alina Marie Hasbi, Yuichi Otsuka

    2014 International Conference on Electronics, Information and Communications (ICEIC)     2014年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Malaysia is located at equatorial region, which is from 3 degrees to 8 degrees South of the magnetic equator where equatorial plasma bubbles (EPBs) frequently occur. EPBs could disrupt radio communication and navigational systems in this region. We present the two-dimensional structure of EPBs observed using GPS networks over South East Asia (SEA) near the equatorial region. 59 days with EPB structure were observed using GPS networks in 2011. The results show that; 1) the initial EPBs onset time occurs mostly after post-sunset between 1900 to 2100 local time (LT); 2) the duration of the occurrences of EPB is mostly from 3 to 6 hours; 3) the GPS networks in SEA region are able to observe east-west size of EPBs from 50 km to 650 km with accuracy +/-50 km.

    Web of Science

  250. 赤道大気レーダーを用いた高度150km沿磁力線不規則構造のドリフト速度に関する研究 査読有り

    大塚雄一, 水谷徳仁, 塩川和夫, Amit Patra, 横山竜宏, 山本衛

    南極資料   57 巻 ( 3 ) 頁: 369-378   2013年11月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)  

  251. Typhoon-induced concentric airglow structures in the mesopause region 査読有り

    S. Suzuki, S. L. Vadas, K. Shiokawa, Y. Otsuka, S. Kawamura, Y. Murayama

    Geophysical Research Letters   40 巻 ( 22 ) 頁: 5983 - 5987   2013年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We present the first reported gravity wave patterns in the mesopause region caused by a typhoon in the troposphere. On 10 December 2002, concentric rings of gravity waves in OH airglow were observed simultaneously by all-sky imagers in the Optical Mesosphere and Thermosphere Imager system in Japan, located at Rikubetsu (43.5°N, 143.8°E), Shigaraki (34.9°N, 136.1°E), and Sata (31.0°N, 130.7°E). The airglow structures, which were well defined and formed a coherent wave pattern expanding concentrically, were identified over 8 h (2135-2947 LT). We estimate the horizontal wavelength, horizontal phase speed, and wave period as 34.5 km, 50.2 m s-1, and 11.5 min, respectively. Infrared cloud images from the Geostationary Meteorological Satellite show that the center of the rings estimated from the airglow data corresponds to a spiral band of Typhoon Pongsona (T0226). This unique event provides new insight into coupling between the lower and upper atmosphere. ©2013. American Geophysical Union. All Rights Reserved.

    DOI: 10.1002/2013GL058087

    Scopus

  252. Typhoon-induced concentric airglow structures in the mesopause region 査読有り

    S. Suzuki, S. L. Vadas, K. Shiokawa, Y. Otsuka, S. Kawamura, Y. Murayama

    GEOPHYSICAL RESEARCH LETTERS   40 巻 ( 22 ) 頁: 5983 - 5987   2013年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We present the first reported gravity wave patterns in the mesopause region caused by a typhoon in the troposphere. On 10 December 2002, concentric rings of gravity waves in OH airglow were observed simultaneously by all-sky imagers in the Optical Mesosphere and Thermosphere Imager system in Japan, located at Rikubetsu (43.5 degrees N, 143.8 degrees E), Shigaraki (34.9 degrees N, 136.1 degrees E), and Sata (31.0 degrees N, 130.7 degrees E). The airglow structures, which were well defined and formed a coherent wave pattern expanding concentrically, were identified over 8 h (2135-2947 LT). We estimate the horizontal wavelength, horizontal phase speed, and wave period as 34.5 km, 50.2 m s(-1), and 11.5 min, respectively. Infrared cloud images from the Geostationary Meteorological Satellite show that the center of the rings estimated from the airglow data corresponds to a spiral band of Typhoon Pongsona (T0226). This unique event provides new insight into coupling between the lower and upper atmosphere.

    DOI: 10.1002/2013GL058087

    Web of Science

  253. Two-dimensional simulation of ionospheric variations in the vicinity of the epicenter of the Tohoku-oki earthquake on 11 March 2011 査読有り

    Shinagawa, H; Tsugawa, T; Matsumura, M; Iyemori, T; Saito, A; Maruyama, T; Jin, H; Nishioka, M; Otsuka, Y

    GEOPHYSICAL RESEARCH LETTERS   40 巻 ( 19 ) 頁: 5009 - 5013   2013年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2013GL057627

    Web of Science

  254. Longitudinal characteristics of spread F backscatter plumes observed with the EAR and Sanya VHF radar in Southeast Asia 査読有り

    Guozhu Li, Baiqi Ning, M. A. Abdu, Yuchi Otsuka, T. Yokoyama, M. Yamamoto, Libo Liu

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   118 巻 ( 10 ) 頁: 6544 - 6557   2013年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The development of equatorial plasma irregularity plumes can be well recorded by steerable backscatter radars operated at and off the magnetic equator due to the fact that the vertically extended plume structures are tracers of magnetically north-south aligned larger scale structures. From observations during March 2012, using two low latitude steerable backscatter radars in Southeast Asia, the Equatorial Atmosphere Radar (EAR) (0.2 degrees S, 100.3 degrees E; dip lat 10.4 degrees S) and the Sanya VHF radar (18.4 degrees N, 109.6 degrees E; dip lat 12.8 degrees N), the characteristics of backscatter plumes over the two sites separated in longitude by similar to 1000 km were simultaneously investigated. The beam steering measurements reveal frequent occurrences of multiple plumes over both radar sites, of which two cases are analyzed here. The observations on 30 March 2012 show plume structures initiated within the radar scanned area, followed by others drifting from the west of the radar beam over both stations. A tracing analysis on the onset locations of plasma plumes reveals spatially well-separated backscatter plumes, with a maximum east-west wavelength of about 1000 km, periodically generated in longitudes between 85 degrees E and 110 degrees E. The postsunset backscatter plumes seen by the Sanya VHF radar are found to be due to the passage of sunset plumes initiated around the longitude of EAR. Most interestingly, the EAR measurements on the night of 21 March 2012 show multiple plume structures that developed successively in the radar scanned area with east-west separation of similar to 50 km, with however no sunset plasma plume over Sanya. Colocated ionogram measurements show that spread F irregularities occurred mainly in the bottomside F region at Sanya, whereas satellite traces in ionograms that are indications of large-scale wave structures were observed on that night at both stations. Possible causes for the longitudinal difference in the characteristics of radar backscatter plumes are discussed.

    DOI: 10.1002/jgra.50581

    Web of Science

  255. Observation of nighttime medium-scale travelling ionospheric disturbances by two 630-nm airglow imagers near the auroral zone 査読有り

    Shiokawa, K; Mori, M; Otsuka, Y; Oyama, S; Nozawa, S; Suzuki, S; Connors, M

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   103 巻   頁: 184 - 194   2013年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2013.03.024

    Web of Science

  256. Ionogram-based range-time displays for observing relationships between ionosonde satellite traces, spread F and drifting optical plasma depletions 査読有り

    Lynn, KJW; Otsuka, Y; Shiokawa, K

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   98 巻   頁: 105 - 112   2013年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2013.03.020

    Web of Science

  257. Physical mechanisms of the ionospheric storms at equatorial and higher latitudes during the recovery phase of geomagnetic storms 査読有り

    Balan, N; Otsuka, Y; Nishioka, M; Liu, JY; Bailey, GJ

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   118 巻 ( 5 ) 頁: 2660 - 2669   2013年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/jgra.50275

    Web of Science

    Scopus

  258. Evidence of gravity wave ducting in the mesopause region from airglow network observations 査読有り

    Suzuki, S; Shiokawa, K; Otsuka, Y; Kawamura, S; Murayama, Y

    GEOPHYSICAL RESEARCH LETTERS   40 巻 ( 3 ) 頁: 601 - 605   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2012GL054605

    Web of Science

    Scopus

  259. GPS observations of medium-scale traveling ionospheric disturbances over Europe 査読有り

    Otsuka, Y., Suzuki, K., Nakagawa, S., Nishioka, M., Shiokawa, K., and Tsugawa, T.

    Ann. Geophys.   31 巻   頁: 163-172   2013年2月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Two-dimensional structures of medium-scale traveling ionospheric disturbances (MSTIDs) over Europe have been revealed, for the first time, by using maps of the total electron content (TEC) obtained from more than 800 GPS receivers of the European GPS receiver networks. From statistical analysis of the TEC maps obtained 2008, we have found that the observed MSTIDs can be categorized into two groups: daytime MSTID and nighttime MSTID. The daytime MSTID frequently occurs in winter. Its maximum occurrence rate in monthly and hourly bin exceeds 70% at lower latitudes over Europe, whereas it is approximately 45% at higher latitudes. Since most of the daytime MSTIDs propagate southward, we speculate that they could be caused by atmospheric gravity waves in the thermosphere. The nighttime MSTIDs also frequently occur in winter but most of them propagate southwestward, in a direction consistent with the theory that polarization electric fields play an important role in generating the nighttime MSTIDs. The nighttime MSTID occurrence rate shows distinct latitudinal difference: The maximum of the occurrence rate in monthly and hourly bin is approximately 50% at lower latitudes in Europe, whereas the nighttime MSTID was rarely observed at higher latitudes. We have performed model calculations of the plasma density perturbations caused by a gravity wave and an oscillating electric field to reproduce the daytime and nighttime MSTIDs, respectively. We find that TEC perturbations caused by gravity waves do not show dip angle dependencies, while those caused by the oscillating electric field have a larger amplitude at lower latitudes. These dip angle dependencies of the TEC perturbation amplitude could contribute to the latitudinal variation of the MSTID occurrence rate. Comparing with previous studies, we discuss the longitudinal difference of the nighttime MSTID occurrence rate, along with the E- and F-region coupling processes. The seasonal variation, of the nighttime MSTID occurrence rate in Europe, is not consistent with the theory that the longitudinal and seasonal variations of the nighttime MSTID occurrence could be attributed to those of the Es layer occurrence.

    DOI: doi:10.5194/angeo-31-163-2013

  260. Drift velocities of 150-km field-aligned irregularities observed by the equatorial atmosphere radar 査読有り

    Otsuka Y, Mizutani N, Shiokawa K, Patra A, Yokoyama T, Yamamoto M

    Antarctic Record   57 巻 ( 3 ) 頁: 369 - 378   2013年

  261. IMAP-WG国際宇宙ステーションからの地球超高層大気撮像観測ISS-IMAPミッションの初期成果

    齊藤昭則, 山崎 敦, 阿部琢美, 鈴木 睦, 坂野井 健, 吉川一朗, 大塚雄一, 藤原 均, 田口 真, 山本 衛, 中村卓司, 江尻 省, 菊池雅行, 河野英昭, Huixin Liu, 石井 守, 久保田 実, 津川卓也, 星野尾一明, 坂野井和代

    第13回宇宙科学シンポジウム     2013年

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  262. GPS observations of medium-scale traveling ionospheric disturbances over Europe 査読有り

    Otsuka, Y; Suzuki, K; Nakagawa, S; Nishioka, M; Shiokawa, K; Tsugawa, T

    ANNALES GEOPHYSICAE   31 巻 ( 2 ) 頁: 163 - 172   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-31-163-2013

    Web of Science

  263. Longitudinal characteristics of spread F backscatter plumes observed with the EAR and Sanya VHF radar in Southeast Asia 査読有り

    Guozhu Li, Baiqi Ning, M. A. Abdu, Yuchi Otsuka, T. Yokoyama, M. Yamamoto, Libo Liu

    Journal of Geophysical Research: Space Physics   118 巻 ( 10 ) 頁: 6544 - 6557   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    The development of equatorial plasma irregularity plumes can be well recorded by steerable backscatter radars operated at and off the magnetic equator due to the fact that the vertically extended plume structures are tracers of magnetically north-south aligned larger scale structures. From observations during March 2012, using two low latitude steerable backscatter radars in Southeast Asia, the Equatorial Atmosphere Radar (EAR) (0.2°S, 100.3°E
    dip lat 10.4°S) and the Sanya VHF radar (18.4°N, 109.6°E
    dip lat 12.8°N), the characteristics of backscatter plumes over the two sites separated in longitude by ~1000 km were simultaneously investigated. The beam steering measurements reveal frequent occurrences of multiple plumes over both radar sites, of which two cases are analyzed here. The observations on 30 March 2012 show plume structures initiated within the radar scanned area, followed by others drifting from the west of the radar beam over both stations. A tracing analysis on the onset locations of plasma plumes reveals spatially well-separated backscatter plumes, with a maximum east-west wavelength of about 1000 km, periodically generated in longitudes between 85°E and 110°E. The postsunset backscatter plumes seen by the Sanya VHF radar are found to be due to the passage of sunset plumes initiated around the longitude of EAR. Most interestingly, the EAR measurements on the night of 21 March 2012 show multiple plume structures that developed successively in the radar scanned area with east-west separation of ~50 km, with however no sunset plasma plume over Sanya. Colocated ionogram measurements show that spread F irregularities occurred mainly in the bottomside F region at Sanya, whereas satellite traces in ionograms that are indications of large-scale wave structures were observed on that night at both stations. Possible causes for the longitudinal difference in the characteristics of radar backscatter plumes are discussed. Key Points Simultaneous measurements of ESF plumes by two closely located radars Sunset plume onset and post-sunset periodic plumes are detected by both radars Smaller scale longitudinal differences in the plume occurrence are presented ©2013. American Geophysical Union. All Rights Reserved.

    DOI: 10.1002/jgra.50581

    Scopus

  264. Small-scale ionospheric delay variation associated with plasma bubbles studied with GNSS and optical measurements and its impact on GBAS 査読有り

    S. Saito, T. Yoshihara, Y. Otsuka

    PROCEEDINGS OF THE 26TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS 2013)     頁: 1869 - 1874   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:INST NAVIGATION  

    For differential GNSS systems such as the ground-based augmentation system (GBAS), spatial variation (or spatial gradient) in ionospheric delay is a critical issue.
    In the low latitude region, the dominant ionospheric disturbance is the plasma bubble. Plasma bubbles are local ionospheric depletions that often occur after sunset. They accompany ionospheric irregularities with various scale sizes from 100 km down to a meter. However, the characteristics of the low latitude ionospheric variations in teens of a specific threat to GBAS have not been well studied yet.
    This paper studies the spatial relationship between the ionospheric delay gradients and the large-scale plasma bubble structure. The ionospheric delay gradients are measured with spaced receivers at Ishigaki, Japan. Large-scale plasma bubble structures are measured with an all-sky airglow images observed at Yonaguni, Japan.
    The ionospheric delay gradients are shown to have large values at the edges of plasma bubbles, and theeir directions are consistent with the direction of the electron density gradient inferred from the airglow images as well as the expectation that the gradient.
    In some cases, however, the ionospheric delay gradients have large values had large values at locations other than the plasma bubble edges. The absolute ionospheric delay with dual-frequency measurements and the drift velocity will be analyzed to investigate the scale size and the amplitude of the irregularities that cause the ionospheric delay gradients. Co-site observations of the ionospheric delay gradient and the airglow at Ishigaki to have nearly common line of sights for both the measurements.

    Web of Science

  265. A comparative study of equatorial daytime vertical E x B drift in the Indian and Indonesian sectors based on 150 km echoes 査読有り

    A. K. Patra, P. Pavan Chaitanya, N. Mizutani, Y. Otsuka, T. Yokoyama, M. Yamamoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    In this paper, we study for the first time the daytime vertical E x B drift velocities from Gadanki and Kototabang using the Doppler shifts of the 150-km echoes observed during 2008-2010, a period of low solar activity. Drift velocities are mostly positive and confined to 35 m s(-1) at both the locations, except for Gadanki where on a few occasions negative drift velocities have been observed in the afternoon hours. Drift velocities generally show a decreasing trend with local time and the largest drift is generally observed in the forenoon hours consistent with extensively reported observations and models of E x B drift. Drift velocities from Gadanki and Kototabang compared exceeding well on some days and differed remarkably on many days despite the fact that they are longitudinally separated by only 20 degrees. The day-to-day variation in the drift velocity could be as high as 15 m s(-1) at Gadanki and 7 m s(-1) at Kototabang. Seasonal mean drifts over Gadanki are found to be generally larger than those of Kototabang. The observations have been compared in detail with those reported earlier based on ground- and satellite- based observations and also with the Scherliess-Fejer model. The observed differences in the drifts at the two locations, including the downward drifts, have been discussed in the light of current understanding of the longitudinal variability of E x B drift.

    DOI: 10.1029/2012JA018053

    Web of Science

  266. Motion of high-latitude nighttime medium-scale traveling ionospheric disturbances associated with auroral brightening 査読有り

    Shiokawa, K, Mori, M, Otsuka, Y, Oyama, S, Nozawa, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年10月

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  267. Motion of high-latitude nighttime medium-scale traveling ionospheric disturbances associated with auroral brightening 査読有り

    Shiokawa K, Mori M, Otsuka Y, Oyama S, Nozawa S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年10月

  268. Observation of equatorial nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow images over 7 years 査読有り

    D. Fukushima, K. Shiokawa, Y. Otsuka, T. Ogawa

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We report on nighttime medium- scale traveling ionospheric disturbances (MSTIDs) observed at Kototabang, Indonesia (geographic longitude: 100.3 degrees E; geographic latitude: 0.2 degrees S; and geomagnetic latitude: 10.6 degrees S) during a 7-year period from October 2002 to October 2009. MSTIDs were observed in 630-nm nighttime airglow images by using a highly sensitive all-sky airglow imager at Kototabang. The averages and standard deviations of horizontal phase velocity, period, and horizontal wavelength of MSTIDs observed during the 7 years were 320 +/- 170 m/s, 42 +/- 11 min, and 790 +/- 440 km, respectively. The occurrence rate of the observed MSTIDs decreased with decreasing solar activity. The average horizontal wavelength of MSTIDs increased with decreasing solar activity. Southward MSTIDs were dominant throughout the 7 years of observations. These facts are consistent with the hypothesis that the observed MSTIDs are caused by gravity waves in the thermosphere. Moreover, we compared the propagation directions of the observed MSTIDs with the locations of tropospheric convection activity for the events where gravity waves producing the observed MSTIDs could have existed in the lower atmosphere. Strong tropospheric convection was found within +/- 30 degrees from the source directions of MSTIDs in 81% of the MSTID events. In such events, gravity waves were possibly generated from deep convection in the troposphere and directly propagated into the thermosphere.

    DOI: 10.1029/2012JA017758

    Web of Science

  269. On post-midnight field-aligned irregularities observed with a 30.8-MHz radar at a low latitude: Comparison with F-layer altitude near the geomagnetic equator 査読有り

    M. Nishioka, Y. Otsuka, K. Shiokawa, T. Tsugawa, Effendy, P. Supnithi, T. Nagatsuma, K. T. Murata

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We investigated the relationship between post-midnight F-region field aligned irregularities (FAIs) and F-layer altitude by analyzing data of a 30.8-MHz radar installed 5at Kototabang, Indonesia (0.2 degrees S, 100.3 degrees E; geomagnetic latitude 10.4 degrees S) and an ionosonde installed at Chumphon, Thailand (10.7 degrees N, 99.4 degrees E; geomagnetic latitude 3.3 degrees N). Chumphon is located near the geomagnetic equator on approximately the same meridian as Kototabang. Case studies show that the altitude of the F-layer rose at Chumphon a half hour before the post-midnight FAIs appeared at Kototabang. The Doppler velocity of the E-region FAIs observed simultaneously by the 30.8-MHz radar was downward, indicating that the F-layer uplift was not caused by the electric field. We also investigated seasonal variations of the post-midnight FAI occurrence and the F-layer altitude. Both the post-midnight FAIs and the uplift of the F-layer were frequently seen around midnight between May and August. The seasonal variation of the midnight F-layer uplift around the geomagnetic equator coincided with that of the post-midnight FAI occurrence at Kototabang. These results suggest that the uplift of the F-layer would play an important role in the generation of post-midnight FAIs. We evaluated the linear growth rate of the Rayleigh-Taylor instability based on the altitude of the F-layer observed at Chumphon. The result shows that the uplift of the F-layer can enhance the growth rate because gravity-driven eastward electric current increases. Therefore, we interpret that the observed FAIs were accompanied by plasma bubble, the growth rate of which was reinforced by the uplifted F-layer.

    DOI: 10.1029/2012JA017692

    Web of Science

  270. Response of low-latitude ionosphere to medium-term changes of solar and geomagnetic activity 査読有り

    Ivan Kutiev, Yuichi Otsuka, Dora Pancheva, Rod Heelis

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The paper presents the medium-term quasi periodic (similar to 9-27 day) response of middle and low-latitude ionosphere to solar [F10.7) and geomagnetic (Kp-index) forcing. The ionospheric response is examined by wavelet analysis of the relative deviations of TEC over Japan for the period of time 2000-2008. It is found that the similar to 27-day rTEC oscillations correlate well with the same oscillations of the solar index F10.7 particularly in the solar maximum and its early declining phase (2001-2005). During the declining phase of solar activity (for example, year of 2005) the Kp-index variability exhibits additionally strong oscillations with periods 13.5- and 9-days. Similar oscillations are found in rTEC as well but they do not follow the geomagnetic forcing as faithfully as those associated with F10.7. During solar minimum the quasi periodic rTEC variability is shaped mainly by the recurrent geomagnetic activity. An attempt is made to investigate the latitudinal dependence of the similar to 9-27-day rTEC response over Japan as well as the phase relationship between the forcing and response.

    DOI: 10.1029/2012JA017641

    Web of Science

  271. Disappearance of equatorial plasma bubble after interaction with mid-latitude medium-scale traveling ionospheric disturbance 査読有り

    Otsuka, Y., K. Shiokawa, and T. Ogawa

    Geophys. Res. Lett.   39 巻 ( L14105 )   2012年7月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: doi:10.1029/2012GL052286

  272. Disappearance of equatorial plasma bubble after interaction with mid-latitude medium-scale traveling ionospheric disturbance 査読有り

    Otsuka, Y; Shiokawa, K; Ogawa, T

    GEOPHYSICAL RESEARCH LETTERS   39 巻   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2012GL052286

    Web of Science

  273. Overview of Nighttime Ionospheric Instabilities at Low- and Mid-Latitudes: Coupling Aspects Resulting in Structuring at the Mesoscale 査読有り

    Makela, JJ; Otsuka, Y

    SPACE SCIENCE REVIEWS   168 巻 ( 1-4 ) 頁: 419 - 440   2012年6月

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    記述言語:英語  

    DOI: 10.1007/s11214-011-9816-6

    Web of Science

  274. GPS total electron content variations associated with poleward moving Sun-aligned arcs 査読有り

    P. T. Jayachandran, K. Hosokawa, K. Shiokawa, Y. Otsuka, C. Watson, S. C. Mushini, J. W. MacDougall, P. Prikryl, R. Chadwick, T. D. Kelly

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    GPS total electron content (TEC) has shown quasiperiodic oscillations of varying amplitude associated with poleward moving Sun-aligned arcs. The amplitude of TEC variations showed a maximum of similar to 3 TECU and seemed to decrease as the arcs moved poleward from the source/generation region. Simultaneous DMSP data showed that fluctuations in TEC and optical intensification were caused by precipitation of high-energy (>500 eV) particles. Concurrent ionosonde observations also exhibited quasiperiodic variations (within limit of the resolution of the data) in peak ionospheric electron density of the ionosphere. Bottom height of the ionospheric layers produced by precipitating particles varied between 130 km (upper E region) and 300 km (F region), indicating variable particle precipitation energy. Frequency analysis of high-resolution TEC data showed a broad range of discrete frequency components from 1.60 mHz to 22.80 mHz present in the TEC oscillations, which may provide insight into the energization/modulation of precipitating particles by these oscillations. A broad distribution of equivalent vertical thickness of arcs was calculated using GPS TEC and ionosonde measurements of peak electron density. This distribution showed a minimum thickness of 21 km, a maximum of 84 km, and an average of 49 km. The equivalent vertical thickness also showed a linear relationship with bottomside height of the ionospheric layer (auroral arc). The relationship showed an increase in the vertical thickness with an increase in bottomside height of the layer. This relationship is a consequence of variations in the energy of the precipitating particles causing different ionospheric production profiles.

    DOI: 10.1029/2011JA017423

    Web of Science

  275. VHF Radar Observations of Post-Midnight F-Region Field-Aligned Irregularities over Indonesia during Solar Minimum 査読有り

    Otsuka, Y., K. Shiokawa, M. Nishioka and Effendy

    Indian Journal of Radio and Space Physics (IJRSP)   ( 41 ) 頁: 199-207   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  276. VHF Radar Observations of Post-Midnight F-Region Field-Aligned Irregularities over Indonesia during Solar Minimum 査読有り

    Otsuka, Y, K. Shiokawa, M. Nishioka, Effendy

    Indian Journal of Radio and Space Physics (IJRSP)   ( 41 ) 頁: 199-207   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  277. Seasonal and Local Time Variations of E-Region Field-Aligned Irregularities Observed with 30.8-MHz Radar at Kototabang, Indonesia 査読有り

    Otsuka, Y.

    International Journal of Geophysics   2012 巻 ( 695793 )   2012年3月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: doi:10.1155/2012/695793

  278. Polarization of Pc1/EMIC waves and related proton auroras observed at subauroral latitudes 査読有り

    R. Nomura, K. Shiokawa, K. Sakaguchi, Y. Otsuka, M. Connors

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We have investigated the polarization of Pc1 geomagnetic pulsations and related proton auroras at subauroral latitudes, using an induction magnetometer and an all-sky camera at Athabasca, Canada (54.7 degrees N, 246.7 degrees E, magnetic latitude (mlat) 61.7 degrees N). Isolated proton auroras often appear in association with Pc1 pulsations, because of proton scattering by electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. We used the proton aurora as a proxy for the location and size of the Pc1 ionospheric source. For 27 Pc1 events with simultaneously observed proton auroras over 4 years from September 7, 2005 to September 6, 2009, we calculated the distances between the Pc1 ionospheric source and the observation site, normalized by the scale size of the source. We tried three different definitions of the scale size of Pc1 ionospheric source to calculate the normalized distances. We found that the rotation angle theta between the Pc1 polarization ellipse and the direction to the proton aurora changes from 90 degrees to 0 degrees as the normalized distance increases. For the definition of the scale sizes that gives most clear theta-transition from 90 degrees to 0 degrees, the transition occurs at the normalized distance similar to 2.0-4.0, while it was similar to 1.0-2.0 by the model calculation of Fujita and Tamao (1988). The averaged major axes tend to point toward the proton aurora at larger distances. The difference of the transition location may imply that the Pc1 ionospheric sources are larger than the isolated proton auroras, or that the inhomogenuity of the ionospheric conductivity by the proton precipitation affects the transition distances.

    DOI: 10.1029/2011JA017241

    Web of Science

  279. Ionospheric and thermospheric storms at equatorial latitudes observed by CHAMP, ROCSAT, and DMSP 査読有り

    N. Balan, J. Y. Liu, Y. Otsuka, S. Tulasi Ram, H. Luehr

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻   2012年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Analysis of the dayside electron density (Ne) and neutral mass density (N) at 400 km height measured by CHAMP during 12 intense geomagnetic storms in 2000-2004, and ion densities at 600 km and 840 km heights measured by ROCSAT and DMSP during a few of the intense storms, reveal some new aspects. Thermospheric storms (change of N) reach the equator within 1.5 to 3 hours from the main phase (MP) onset of intense storms having short and steady MPs. The responses of the equatorial ionosphere (at CHAMP) to both MPs and RPs (recovery phases) of the storms are generally opposite to those at higher latitudes. In addition to the known opposite responses during MPs, the analysis reveals that positive ionospheric storms develop at equatorial latitudes (within about +/- 15 degrees magnetic latitudes) during daytime RPs, while conventional negative storms occur at higher latitudes. Ionospheric storms also extend to the topside ionosphere beyond 850 km height and are generally positive (at DMSP), especially during MPs. The positive storms around the equatorial ionospheric peak during RPs are interpreted in terms of the potential sources such as (1) zero or westward electric fields due to disturbance dynamo and/or prompt penetration, (2) plasma convergence due to the mechanical effects of storm-time equatorward neutral winds and waves, (3) increase of atomic oxygen density and decrease of molecular nitrogen density due to the downwelling effect of the winds, and (4) photoionization. The positive storms in the topside ionosphere during MPs involve the rapid upward drift of plasma due to eastward PPEFs, reduction in the downward diffusion of plasma along the field lines, and plasma convergence due to equatorward winds and waves.

    DOI: 10.1029/2011JA016903

    Web of Science

  280. A comparative study of equatorial daytime vertical e × B drift in the Indian and Indonesian sectors based on 150 km echoes 査読有り

    A. K. Patra, P. Pavan Chaitanya, N. Mizutani, Y. Otsuka, T. Yokoyama, M. Yamamoto

    Journal of Geophysical Research: Space Physics   117 巻 ( 11 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In this paper, we study for the first time the daytime vertical E × B drift velocities from Gadanki and Kototabang using the Doppler shifts of the 150-km echoes observed during 2008-2010, a period of low solar activity. Drift velocities are mostly positive and confined to 35 m s-1 at both the locations, except for Gadanki where on a few occasions negative drift velocities have been observed in the afternoon hours. Drift velocities generally show a decreasing trend with local time and the largest drift is generally observed in the forenoon hours consistent with extensively reported observations and models of E × B drift. Drift velocities from Gadanki and Kototabang compared exceeding well on some days and differed remarkably on many days despite the fact that they are longitudinally separated by only 20. The day-to-day variation in the drift velocity could be as high as 15 m s-1 at Gadanki and 7 m s-1 at Kototabang. Seasonal mean drifts over Gadanki are found to be generally larger than those of Kototabang. The observations have been compared in detail with those reported earlier based on ground-and satellite-based observations and also with the Scherliess-Fejer model. The observed differences in the drifts at the two locations, including the downward drifts, have been discussed in the light of current understanding of the longitudinal variability of E × B drift.

    DOI: 10.1029/2012JA018053

    Scopus

  281. Development of low-cost sky-scanning Fabry-Perot interferometers for airglow and auroral studies 査読有り

    Shiokawa, K; Otsuka, Y; Oyama, S; Nozawa, S; Satoh, M; Katoh, Y; Hamaguchi, Y; Yamamoto, Y; Meriwether, J

    EARTH PLANETS AND SPACE   64 巻 ( 11 ) 頁: 1033 - 1046   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2012.05.004

    Web of Science

  282. GPS total electron content variations associated with poleward moving Sun-aligned arcs 査読有り

    P. T. Jayachandran, K. Hosokawa, K. Shiokawa, Y. Otsuka, C. Watson, S. C. Mushini, J. W. MacDougall, P. Prikryl, R. Chadwick, T. D. Kelly

    Journal of Geophysical Research: Space Physics   117 巻 ( 5 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    GPS total electron content (TEC) has shown quasiperiodic oscillations of varying amplitude associated with poleward moving Sun-aligned arcs. The amplitude of TEC variations showed a maximum of ∼3 TECU and seemed to decrease as the arcs moved poleward from the source/generation region. Simultaneous DMSP data showed that fluctuations in TEC and optical intensification were caused by precipitation of high-energy (&gt
    500 eV) particles. Concurrent ionosonde observations also exhibited quasiperiodic variations (within limit of the resolution of the data) in peak ionospheric electron density of the ionosphere. Bottom height of the ionospheric layers produced by precipitating particles varied between 130km (upper E region) and 300km (F region), indicating variable particle precipitation energy. Frequency analysis of high-resolution TEC data showed a broad range of discrete frequency components from 1.60 mHz to 22.80 mHz present in the TEC oscillations, which may provide insight into the energization/modulation of precipitating particles by these oscillations. A broad distribution of equivalent vertical thickness of arcs was calculated using GPS TEC and ionosonde measurements of peak electron density. This distribution showed a minimum thickness of 21km, a maximum of 84km, and an average of 49km. The equivalent vertical thickness also showed a linear relationship with bottomside height of the ionospheric layer (auroral arc). The relationship showed an increase in the vertical thickness with an increase in bottomside height of the layer. This relationship is a consequence of variations in the energy of the precipitating particles causing different ionospheric production profiles. Copyright 2012 by the American Geophysical Union.

    DOI: 10.1029/2011JA017423

    Scopus

  283. Early observation and future plan of the Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere mapping observation mission

    SAITO Akinori, YAMAZAKI Atsushi, SAKANOI Takeshi, YOSHIKAWA Ichiro, ABE Takumi, OTSUKA Yuichi, TAGUCHI Makoto, SUZUKI Makoto, KIKUCHI Masayuki, NAKAMURA Takuji, YAMAMOTO Mamoru, KAWANO Hideaki, LIU Huixin, ISHII Mamoru, TSUGAWA Takuya, SAKANOI Kazuyo, FUJIWARA Hitoshi, KUBOTA Minoru, EJIRI Mitsumu K, SAITO Akinori

    地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM)   132nd 巻   頁: ROMBUNNO.B005-18   2012年

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    記述言語:英語  

    J-GLOBAL

  284. Ionospheric and thermospheric storms at equatorial latitudes observed by CHAMP, ROCSAT, and DMSP 査読有り

    N. Balan, J. Y. Liu, Y. Otsuka, S. Tulasi Ram, H. Lühr

    Journal of Geophysical Research: Space Physics   117 巻 ( 1 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    Analysis of the dayside electron density (Ne) and neutral mass density (N) at 400km height measured by CHAMP during 12 intense geomagnetic storms in 2000-2004, and ion densities at 600km and 840km heights measured by ROCSAT and DMSP during a few of the intense storms, reveal some new aspects. Thermospheric storms (change of N) reach the equator within 1.5 to 3 hours from the main phase (MP) onset of intense storms having short and steady MPs. The responses of the equatorial ionosphere (at CHAMP) to both MPs and RPs (recovery phases) of the storms are generally opposite to those at higher latitudes. In addition to the known opposite responses during MPs, the analysis reveals that positive ionospheric storms develop at equatorial latitudes (within about ±15° magnetic latitudes) during daytime RPs, while conventional negative storms occur at higher latitudes. Ionospheric storms also extend to the topside ionosphere beyond 850km height and are generally positive (at DMSP), especially during MPs. The positive storms around the equatorial ionospheric peak during RPs are interpreted in terms of the potential sources such as (1) zero or westward electric fields due to disturbance dynamo and/or prompt penetration, (2) plasma convergence due to the mechanical effects of storm-time equatorward neutral winds and waves, (3) increase of atomic oxygen density and decrease of molecular nitrogen density due to the downwelling effect of the winds, and (4) photoionization. The positive storms in the topside ionosphere during MPs involve the rapid upward drift of plasma due to eastward PPEFs, reduction in the downward diffusion of plasma along the field lines, and plasma convergence due to equatorward winds and waves.

    DOI: 10.1029/2011JA016903

    Scopus

  285. On post-midnight field-aligned irregularities observed with a 30.8-MHz radar at a low latitude: Comparison with F-layer altitude near the geomagnetic equator 査読有り

    M. Nishioka, Y. Otsuka, K. Shiokawa, T. Tsugawa, Null Effendy, P. Supnithi, T. Nagatsuma, K. T. Murata

    Journal of Geophysical Research: Space Physics   117 巻 ( 8 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    We investigated the relationship between post-midnight F-region field aligned irregularities (FAIs) and F-layer altitude by analyzing data of a 30.8-MHz radar installed 5at Kototabang, Indonesia (0.2S, 100.3E
    geomagnetic latitude 10.4S) and an ionosonde installed at Chumphon, Thailand (10.7N, 99.4E
    geomagnetic latitude 3.3N). Chumphon is located near the geomagnetic equator on approximately the same meridian as Kototabang. Case studies show that the altitude of the F-layer rose at Chumphon a half hour before the post-midnight FAIs appeared at Kototabang. The Doppler velocity of the E-region FAIs observed simultaneously by the 30.8-MHz radar was downward, indicating that the F-layer uplift was not caused by the electric field. We also investigated seasonal variations of the post-midnight FAI occurrence and the F-layer altitude. Both the post-midnight FAIs and the uplift of the F-layer were frequently seen around midnight between May and August. The seasonal variation of the midnight F-layer uplift around the geomagnetic equator coincided with that of the post-midnight FAI occurrence at Kototabang. These results suggest that the uplift of the F-layer would play an important role in the generation of post-midnight FAIs. We evaluated the linear growth rate of the Rayleigh-Taylor instability based on the altitude of the F-layer observed at Chumphon. The result shows that the uplift of the F-layer can enhance the growth rate because gravity-driven eastward electric current increases. Therefore, we interpret that the observed FAIs were accompanied by plasma bubble, the growth rate of which was reinforced by the uplifted F-layer. © 2012. American Geophysical Union. All Rights Reserved.

    DOI: 10.1029/2012JA017692

    Scopus

  286. Observation of equatorial nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow images over 7 years 査読有り

    D. Fukushima, K. Shiokawa, Y. Otsuka, T. Ogawa

    Journal of Geophysical Research: Space Physics   117 巻 ( 10 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    [1] We report on nighttime medium-scale traveling ionospheric disturbances (MSTIDs) observed at Kototabang, Indonesia (geographic longitude: 100.3°E
    geographic latitude: 0.2°S
    and geomagnetic latitude: 10.6°S) during a 7-year period from October 2002 to October 2009. MSTIDs were observed in 630-nm nighttime airglow images by using a highly sensitive all-sky airglow imager at Kototabang. The averages and standard deviations of horizontal phase velocity, period, and horizontal wavelength of MSTIDs observed during the 7 years were 320 ±170 m/s, 42 ±11 min, and 790 ± 440 km, respectively. The occurrence rate of the observed MSTIDs decreased with decreasing solar activity. The average horizontal wavelength of MSTIDs increased with decreasing solar activity. Southward MSTIDs were dominant throughout the 7 years of observations. These facts are consistent with the hypothesis that the observed MSTIDs are caused by gravity waves in the thermosphere. Moreover, we compared the propagation directions of the observed MSTIDs with the locations of tropospheric convection activity for the events where gravity waves producing the observed MSTIDs could have existed in the lower atmosphere. Strong tropospheric convection was found within ±30 degrees from the source directions of MSTIDs in 81% of the MSTID events. In such events, gravity waves were possibly generated from deep convection in the troposphere and directly propagated into the thermosphere. © 2012. American Geophysical Union. All Rights Reserved.

    DOI: 10.1029/2012JA017758

    Scopus

  287. Motion of high-latitude nighttime medium-scale traveling ionospheric disturbances associated with auroral brightening 査読有り

    K. Shiokawa, M. Mori, Y. Otsuka, S. Oyama, S. Nozawa

    Journal of Geophysical Research: Space Physics   117 巻 ( 10 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    We report for the first time the rapid oscillating motion of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) based on airglow imaging observations at Troms (magnetic latitude: 67.1N), Norway on 8 December, 2009. The MSTIDs appeared in 630-nm airglow images at 1530 UT as wave-like structures south of Troms with a horizontal wavelength of ∼200km and a phase surface of north to south. They moved eastward with velocities of 30-60m/s. The velocity was faster in the poleward-side of the MSTIDs, forming a northeast-southwest phase surface at later times. This phase surface direction is opposite to that of midlatitude MSTIDs. The MSTIDs show sudden oscillations and phase jump in the east-west direction with a timescale of ∼10min at 1730 UT. The oscillations were associated with an auroral brightening observed at the poleward edge of the images and small magnetic field perturbations observed by ground magnetometers. The Doppler measurement of the 630-nm airglow by a Fabry-Perot interferometer at Troms showed a stable southeastward thermospheric wind with a velocity of ∼150m/s. These observations indicate that the MSTID oscillations were linked to auroral electric field in the ionosphere, implying that the observed MSTIDs are ionospheric plasma structures. We suggest that the observed MSTIDs were created by atmospheric gravity waves at the beginning, left as fossil plasma structures even after the gravity wave packet dissipated in the thermosphere, moved eastward according to the background electric field driven by the F-region dynamo, and oscillated associated with the auroral electric field. © 2012. American Geophysical Union. All Rights Reserved.

    DOI: 10.1029/2012JA017928

    Scopus

  288. Low-latitude mesosphere, thermosphere, and ionosphere 査読有り

    Y. Sahai, R. S. Dabas, Y. Otsuka, M. Klimenko

    International Journal of Geophysics   2012 巻   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1155/2012/671240

    Scopus

  289. Polarization of Pc1/EMIC waves and related proton auroras observed at subauroral latitudes 査読有り

    R. Nomura, K. Shiokawa, K. Sakaguchi, Y. Otsuka, M. Connors

    Journal of Geophysical Research: Space Physics   117 巻 ( 2 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    We have investigated the polarization of Pc1 geomagnetic pulsations and related proton auroras at subauroral latitudes, using an induction magnetometer and an all-sky camera at Athabasca, Canada (54.7°N, 246.7°E, magnetic latitude (mlat) 61.7°N). Isolated proton auroras often appear in association with Pc1 pulsations, because of proton scattering by electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. We used the proton aurora as a proxy for the location and size of the Pc1 ionospheric source. For 27 Pc1 events with simultaneously observed proton auroras over 4years from September 7, 2005 to September 6, 2009, we calculated the distances between the Pc1 ionospheric source and the observation site, normalized by the scale size of the source. We tried three different definitions of the scale size of Pc1 ionospheric source to calculate the normalized distances. We found that the rotation angle θ between the Pc1 polarization ellipse and the direction to the proton aurora changes from 90° to 0° as the normalized distance increases. For the definition of the scale sizes that gives most clear θ-transition from 90° to 0°, the transition occurs at the normalized distance ∼2.0-4.0, while it was ∼1.0-2.0 by the model calculation of Fujita and Tamao (1988). The averaged major axes tend to point toward the proton aurora at larger distances. The difference of the transition location may imply that the Pc1 ionospheric sources are larger than the isolated proton auroras, or that the inhomogenuity of the ionospheric conductivity by the proton precipitation affects the transition distances. Copyright 2012 by the American Geophysical Union.

    DOI: 10.1029/2011JA017241

    Scopus

  290. Seasonal and local time variations of e -Region field-aligned irregularities observed with 30.8-mhz radar at kototabang, indonesia 査読有り

    Y. Otsuka

    International Journal of Geophysics   2012 巻   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A VHF backscatter radar with operating frequency 30.8 MHz has been operated at Kototabang (0.20°S, 100.32°E
    dip latitude 10.36°S), Indonesia, since February 2006. We analyzed E-region field-aligned irregularities (FAIs) observed by this radar through a year of 2007 and found that the E-region FAI observed at Kototabang can be classified into two groups. One is "descending FAI". Altitude of the FAI echo region descends with time from 102 km to 88 km altitude during 0700-1000 and 1900-0000 LT in June solstice season. The other is "low-altitude FAI", which is observed in an altitude range from 88 to 94 km mainly during nighttime. The observed Doppler velocity show distinct local time and altitude dependence. The seasonally averaged zonal velocity above (below) approximately 94 km altitude is westward (eastward) during daytime and eastward (westward) during nighttime. Meridional/vertical velocity perpendicular to the geomagnetic fields is upward during daytime and downward during nighttime. The direction of the FAI velocity above approximately 94 km altitude is consistent with that of the background E × B plasma drifts reported previously. © 2012 Y. Otsuka.

    DOI: 10.1155/2012/695793

    Scopus

  291. Response of low-latitude ionosphere to medium-term changes of solar and geomagnetic activity 査読有り

    Ivan Kutiev, Yuichi Otsuka, Dora Pancheva, Rod Heelis

    Journal of Geophysical Research: Space Physics   117 巻 ( 8 )   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    The paper presents the medium-term quasi periodic (∼9-27 day) response of middle and low-latitude ionosphere to solar [F10.7) and geomagnetic (Kp-index) forcing. The ionospheric response is examined by wavelet analysis of the relative deviations of TEC over Japan for the period of time 2000-2008. It is found that the ∼27-day rTEC oscillations correlate well with the same oscillations of the solar index F10.7 particularly in the solar maximum and its early declining phase (2001-2005). During the declining phase of solar activity (for example, year of 2005) the Kp-index variability exhibits additionally strong oscillations with periods 13.5- and 9-days. Similar oscillations are found in rTEC as well but they do not follow the geomagnetic forcing as faithfully as those associated with F10.7. During solar minimum the quasi periodic rTEC variability is shaped mainly by the recurrent geomagnetic activity. An attempt is made to investigate the latitudinal dependence of the ∼9-27-day rTEC response over Japan as well as the phase relationship between the forcing and response. © 2012. American Geophysical Union. All Rights Reserved.

    DOI: 10.1029/2012JA017641

    Scopus

  292. Simultaneous observations at Darwin of equatorial bubbles by ionosonde-based range/time displays and airglow imaging 査読有り

    Lynn, KJW; Otsuka, Y; Shiokawa, K

    GEOPHYSICAL RESEARCH LETTERS   38 巻   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2011GL049856

    Web of Science

  293. On postmidnight low-latitude ionospheric irregularities during solar minimum: 1. Equatorial Atmosphere Radar and GPS-TEC observations in Indonesia 査読有り

    T. Yokoyama, M. Yamamoto, Y. Otsuka, M. Nishioka, T. Tsugawa, S. Watanabe, R. F. Pfaff

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Using the 47 MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (10.36 degrees S dip latitude), it is shown that postmidnight irregularities during solar minimum are morphologically different from those detected during solar maximum and are quite similar to those observed with the middle and upper atmosphere (MU) radar in midlatitudes (29.3 degrees N dip latitude). Utilizing the rapid beam-steering capability of the EAR, the spatial structure of the postmidnight irregularities is clearly presented for the first time. It is found that they usually propagate westward and can be categorized into two types. One shows sharp upwelling plumes near local midnight, which should not be a mere passage of fossil plasma bubbles. The other has successive tilted structures which have the same orientation as medium-scale traveling ionospheric disturbances typically observed at midlatitudes. We suggest that the convergence of the equatorward thermospheric wind which is believed to be responsible for the midnight temperature maximum may be an important factor to produce a preferable condition for the upwelling plumes in the postmidnight sector. The displacement between geographic and magnetic equators may also be important for seasonal/longitudinal variation of the postmidnight irregularities.

    DOI: 10.1029/2011JA016797

    Web of Science

  294. On postmidnight low-latitude ionospheric irregularities during solar minimum: 2. C/NOFS observations and comparisons with the Equatorial Atmosphere Radar 査読有り

    T. Yokoyama, R. F. Pfaff, P. A. Roddy, M. Yamamoto, Y. Otsuka

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    A detailed comparison between the observations of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite and the 47 MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (10.36 degrees S dip latitude) on the postmidnight irregularities is presented. The zonal and meridional E x B drift velocities measured by the vector electric field instrument on the C/NOFS are consistent with the westward propagation of backscatter echoes and the line-of-sight Doppler velocities observed with the EAR, respectively. The plasma density depletions are observed in the postmidnight sector for several consecutive orbits, which suggests the depletions grow slowly during the premidnight period and reach the spacecraft altitude around local midnight. The convergence of the equatorward wind which could be responsible for the midnight temperature maximum may produce a preferable condition for the growth of the Rayleigh-Taylor instability around midnight. Electric field fluctuations of medium-scale traveling ionospheric disturbances may play an important role in seeding the instability. Both equatorial and midlatitude-type plasma instabilities could be operational at the EAR latitude sector, which together would foster a high occurrence of postmidnight irregularities during solar minimum.

    DOI: 10.1029/2011JA016798

    Web of Science

  295. Equatorial electrodynamics and neutral background in the Asian sector during the 2009 stratospheric sudden warming 査読有り

    Huixin Liu, Mamoru Yamamoto, S. Tulasi Ram, Takuya Tsugawa, Yuichi Otsuka, Claudia Stolle, Eelco Doornbos, Kiyohumi Yumoto, Tsutomu Nagatsuma

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Using ground observations of total electron content (TEC) and equatorial electrojet (EEJ) in the Asian sector, along with plasma and neutral densities obtained from the CHAMP satellite, we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major stratospheric sudden warming (SSW) in January 2009. Our analysis reveals the following prominent features. First, the TEC response in tropical regions is strongly latitude dependent, with monotonic depletion at the dip equator but a semidiurnal perturbation at low latitudes. Second, the TEC semidiurnal perturbation possesses a significant hemispheric asymmetry in terms of onset date and magnitude. It starts on the same day as the SSW peak in the Northern Hemisphere but 2 days later in the Southern Hemisphere. Its magnitude is twice as strong in the north than in the south. Third, strong counter electrojet occurs in the afternoon, following the strengthening of the eastward EEJ in the morning. Fourth, semidiurnal perturbation in both TEC and EEJ possesses a phase shift, at a rate of about 0.7 h/day. Comparisons with results reported in the Peruvian sector reveal clear longitude dependence in the amplitude and hemispheric asymmetry of the semidiurnal perturbation. Finally, thermospheric density undergoes similar to 25% decrease at low latitudes in the afternoon local time sector during the SSW, indicating significant cooling effects in the tropical upper thermosphere.

    DOI: 10.1029/2011JA016607

    Web of Science

  296. New aspects of thermospheric and ionospheric storms revealed by CHAMP 査読有り

    N. Balan, M. Yamamoto, J. Y. Liu, Y. Otsuka, H. Liu, H. Luehr

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The neutral mass density N and electron density Ne at 400 km height measured by CHAMP during nine intense geomagnetic storms bring out some new aspects of the thermospheric and ionospheric storms. The thermospheric storms (increase of N) develop with the onset of the main phases (MP) of the geomagnetic storms and reach their peak phases before or by the end of the MPs. The ionospheric storms (change of Ne) in general undergo an initial negative phase (with the equatorial ionization anomaly (EIA) crests shifting poleward) before turning positive, and the positive storms reach their peak strengths (or phases) centered at +/- 25 degrees-30 degrees magnetic latitudes; in some (4) cases the positive storms develop without an initial negative phase and with the EIA crests shifting equatorward; in all cases the positive storms reach their peak phases before the end of the MPs and turn to conventional negative storms by the end of the MPs. The observations agree with the different aspects of a physical mechanism of the positive storms. The observations also reveal that the Halloween storms of 30 October 2003 with a short MP without fluctuations produced the strongest positive ionospheric storms through impulsive response, and there is strong equinoctial asymmetry in the ionosphere and thermosphere during geomagnetic storms.

    DOI: 10.1029/2010JA016399

    Web of Science

  297. Decay of polar cap patch 査読有り

    K. Hosokawa, J. I. Moen, K. Shiokawa, Y. Otsuka

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We report an event in which a polar cap patch was detected with an all-sky imager (ASI) at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E; AACGM latitude 82.9 degrees), on the nightside. The patch stopped its antisunward motion associated with a northward turning of interplanetary magnetic field and stayed within the field of view of the ASI for more than 1 h. When the patch stagnated, its luminosity decreased gradually, which allows us to investigate how the patch plasma decayed in a quantitative manner. The decay of the patch can be quantitatively explained by the loss through recombinations of O(+) with ambient N(2) and O(2) molecules, if we assume the altitude of the optical patch to be around 295 km. The derived altitude of the patch around 295 km is much higher than the nominal value at 235 km obtained from the MSIS-E90 and IRI-2007 models, indicating that climatological models such as IRI are not suitable for describing the actual density profile of patches. This is probably because the loss process was much faster in the lower-altitude part of the patch; thus, the peak altitude of the patch increased as it traveled across the polar cap because of rapid recombination at the bottomside of the F region. This suggests that we should employ higher emission altitude when we investigate optical patches transported deep into the nightside polar cap. Such information is important when we compare the optical data with other instruments such as coherent radars and GPS scintillation measurements by mapping the all-sky image on the geographic coordinate system with an assumption of the patch emission altitude.

    DOI: 10.1029/2010JA016297

    Web of Science

  298. A statistical study of the response of the dayside equatorial F-2 layer to the main phase of intense geomagnetic storms as an indicator of penetration electric field 査読有り

    N. Balan, M. Yamamoto, V. Sreeja, I. S. Batista, K. J. W. Lynn, M. A. Abdu, S. Ravindran, T. Kikuchi, Y. Otsuka, K. Shokawa, S. Alex

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The response of the dayside equatorial F-2 layer to the main phases of the 22 intense geomagnetic storms (Dst < -150 nT) in 1998-2008 is investigated using the digital ionosonde data from the equatorial stations in Brazilian, Indian, and Australian longitudes together with equatorial electrojet strength and IMF B-z; the storms include 15 superstorms (Dst < -200 nT). The observations show that there is a period during all MPs when the F-2 layer peak rises (and falls) rapidly with large peak electron density (Nmax) reduction, the rise velocity strongly correlates with the intensity (Dst) of the storms, and the duration of the Nmax reduction corresponds to that of strong eastward electrojet when IMF Bz remains highly negative. The observations indicate the occurrence of strong eastward prompt penetration electric fields (PPEF) during the rapid F-2 layer response. The PPEF drives the F-2 layer peak rapidly upward, which reduces Nmax due to vertical expansion and diffusion. The results therefore suggest that the rapid F-2 layer response (rapid rise (and fall) of peak height (hmax) with large Nmax reduction) observed by ionosondes can be used to detect the occurrence of the daytime eastward PPEF during intense geomagnetic storms irrespective of season and level of solar activity. The data also show two rare events of strong daytime westward electric fields due to disturbance dynamo and/or prompt penetration. The results are important when radars are not available to monitor the occurrence of the PPEF.

    DOI: 10.1029/2010JA016001

    Web of Science

  299. First satellite-imaging observation of medium-scale traveling ionospheric disturbances by FORMOSAT-2/ISUAL 査読有り

    Adachi, T; Otsuka, Y; Yamaoka, M; Yamamoto, M; Shiokawa, K; Chen, AB; Hsu, RR

    GEOPHYSICAL RESEARCH LETTERS   38 巻   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010GL046268

    Web of Science

  300. Vertical connection from the tropospheric activities to the ionospheric longitudinal structure simulated by a new Earth's whole atmosphere-ionosphere coupled model 査読有り

    H. Jin, Y. Miyoshi, H. Fujiwara, H. Shinagawa, K. Terada, N. Terada, M. Ishii, Y. Otsuka, A. Saito

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    This paper introduces a new Earth's atmosphere-ionosphere coupled model that treats seamlessly the neutral atmospheric region from the troposphere to the thermosphere as well as the thermosphere-ionosphere interaction including the electrodynamics self-consistently. The model is especially useful for the study of vertical connection between the meteorological phenomena and the upper atmospheric behaviors. As an initial simulation using the coupled model, we have carried out a 30 day consecutive run in September. The result reveals that the longitudinal structure of the F-region ionosphere varies on a day-to-day basis in a highly complex way and that a four-peak structure of the daytime equatorial ionization anomaly (EIA) similar to the recent observations appears as an averaged feature. The simulation reproduces and thus confirms the vertical coupling processes proposed so far with respect to the formation of the averaged EIA longitudinal structure; the excitation of solar nonmigrating tides in the troposphere, their propagation through the middle atmosphere, and the modulation of ionospheric dynamo, which in turn affects EIA generation. The simulation result indicates that not only the ionospheric averaged longitudinal structure but also the day-to-day variation can be modulated significantly by the lower atmospheric effect.

    DOI: 10.1029/2010JA015925

    Web of Science

  301. Statistical Study of Medium-Scale Traveling Ionospheric Disturbances Observed with a GPS Receiver Network in Japan 査読有り

    Otsuka, Y; Kotake, N; Shiokawa, K; Ogawa, T; Tsugawa, T; Saito, A

    AERONOMY OF THE EARTH'S ATMOSPHERE AND IONOSPHERE   2 巻 ( 3 ) 頁: 291 - 299   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1007/978-94-007-0326-1_21

    Web of Science

  302. A statistical study of the response of the dayside equatorial F2 layer to the main phase of intense geomagnetic storms as an indicator of penetration electric field 査読有り

    N. Balan, M. Yamamoto, V. Sreeja, I. S. Batista, K. J.W. Lynn, M. A. Abdu, S. Ravindran, T. Kikuchi, Y. Otsuka, K. Shokawa, S. Alex

    Journal of Geophysical Research: Space Physics   116 巻 ( 3 )   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    The response of the dayside equatorial F2 layer to the main phases of the 22 intense geomagnetic storms (Dst &lt
    -150 nT) in 1998-2008 is investigated using the digital ionosonde data from the equatorial stations in Brazilian, Indian, and Australian longitudes together with equatorial electrojet strength and IMF Bz
    the storms include 15 superstorms (Dst &lt
    -200 nT). The observations show that there is a period during all MPs when the F2 layer peak rises (and falls) rapidly with large peak electron density (Nmax) reduction, the rise velocity strongly correlates with the intensity (Dst) of the storms, and the duration of the Nmax reduction corresponds to that of strong eastward electrojet when IMF Bz remains highly negative. The observations indicate the occurrence of strong eastward prompt penetration electric fields (PPEF) during the rapid F2 layer response. The PPEF drives the F2 layer peak rapidly upward, which reduces Nmax due to vertical expansion and diffusion. The results therefore suggest that the rapid F2 layer response (rapid rise (and fall) of peak height (hmax) with large Nmax reduction) observed by ionosondes can be used to detect the occurrence of the daytime eastward PPEF during intense geomagnetic storms irrespective of season and level of solar activity. The data also show two rare events of strong daytime westward electric fields due to disturbance dynamo and/or prompt penetration. The results are important when radars are not available to monitor the occurrence of the PPEF. Copyright 2011 by the American Geophysical Union.

    DOI: 10.1029/2010JA016001

    Scopus

  303. Acoustic resonance and plasma depletion detected by GPS total electron content observation after the 2011 off the Pacific coast of Tohoku Earthquake 査読有り

    Saito, A; Tsugawa, T; Otsuka, Y; Nishioka, M; Iyemori, T; Matsumura, M; Saito, S; Chen, CH; Goi, Y; Choosakul, N

    EARTH PLANETS AND SPACE   63 巻 ( 7 ) 頁: 863 - 867   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.034

    Web of Science

  304. Decay of polar cap patch 査読有り

    K. Hosokawa, J. I. Moen, K. Shiokawa, Y. Otsuka

    Journal of Geophysical Research: Space Physics   116 巻 ( 5 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    We report an event in which a polar cap patch was detected with an all-sky imager (ASI) at Resolute Bay, Canada (74.73° N, 265.07° E
    AACGM latitude 82.9°), on the nightside. The patch stopped its antisunward motion associated with a northward turning of interplanetary magnetic field and stayed within the field of view of the ASI for more than 1 h. When the patch stagnated, its luminosity decreased gradually, which allows us to investigate how the patch plasma decayed in a quantitative manner. The decay of the patch can be quantitatively explained by the loss through recombinations of O+ with ambient N2 and O2 molecules, if we assume the altitude of the optical patch to be around 295 km. The derived altitude of the patch around 295 km is much higher than the nominal value at 235 km obtained from the MSIS-E90 and IRI-2007 models, indicating that climatological models such as IRI are not suitable for describing the actual density profile of patches. This is probably because the loss process was much faster in the lower-altitude part of the patch
    thus, the peak altitude of the patch increased as it traveled across the polar cap because of rapid recombination at the bottomside of the F region. This suggests that we should employ higher emission altitude when we investigate optical patches transported deep into the nightside polar cap. Such information is important when we compare the optical data with other instruments such as coherent radars and GPS scintillation measurements by mapping the all-sky image on the geographic coordinate system with an assumption of the patch emission altitude. Copyright 2011 by the American Geophysical Union.

    DOI: 10.1029/2010JA016297

    Scopus

  305. Imaging observation of the Earth's mesosphere, thermosphere and ionosphere by VISI of ISS-IMAP on the International Space Station 査読有り

    Sakanoi, T, Akiya, Y, Yamazaki, A, Otsuka, Y, Saito, A, Yoshikawa, I

    IEEJ Transactions on Fundamentals and Materials   131 巻 ( 12 ) 頁: 983 - 988   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The Institute of Electrical Engineers of Japan  

    We present the scientific targets, instrumental design, principle of measurement, and development of the Visible and near-Infrared Spectral Imager (VISI) which will be launched onto International Space Station (ISS) in January 2012. VISI is equipped with fast optics including a grism, and a high-sensitivity CCD to obtain airglow emissions at wavelengths of O (630 nm), OH Meinel band (650 nm) and O<sub>2</sub> (0-0) atmospheric band (762 nm). VISI has two field-of-views (FOVs), 45 degrees forward and 45 degrees backward to nadir, to subtract background contaminations. The data acquisition of VISI will be continuously performed with short exposure cycle less than several seconds when ISS is orbiting in the night side of the earth, and then provide the seamless line scanning images of the airglows with a spatial resolution better than 50 km. After manufacturing VISI, we checked its performance though optical and electric function tests as well as environmental tests that are necessary to be launched.

    DOI: 10.1541/ieejfms.131.983

    CiNii Books

    その他リンク: https://jlc.jst.go.jp/DN/JALC/00383579674?from=CiNii

  306. Equatorial electrodynamics and neutral background in the Asian sector during the 2009 stratospheric sudden warming 査読有り

    Huixin Liu, Mamoru Yamamoto, S. Tulasi Ram, Takuya Tsugawa, Yuichi Otsuka, Claudia Stolle, Eelco Doornbos, Kiyohumi Yumoto, Tsutomu Nagatsuma

    Journal of Geophysical Research: Space Physics   116 巻 ( 8 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    Using ground observations of total electron content (TEC) and equatorial electrojet (EEJ) in the Asian sector, along with plasma and neutral densities obtained from the CHAMP satellite, we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major stratospheric sudden warming (SSW) in January 2009. Our analysis reveals the following prominent features. First, the TEC response in tropical regions is strongly latitude dependent, with monotonic depletion at the dip equator but a semidiurnal perturbation at low latitudes. Second, the TEC semidiurnal perturbation possesses a significant hemispheric asymmetry in terms of onset date and magnitude. It starts on the same day as the SSW peak in the Northern Hemisphere but 2 days later in the Southern Hemisphere. Its magnitude is twice as strong in the north than in the south. Third, strong counter electrojet occurs in the afternoon, following the strengthening of the eastward EEJ in the morning. Fourth, semidiurnal perturbation in both TEC and EEJ possesses a phase shift, at a rate of about 0.7 h/day. Comparisons with results reported in the Peruvian sector reveal clear longitude dependence in the amplitude and hemispheric asymmetry of the semidiurnal perturbation. Finally, thermospheric density undergoes ∼25% decrease at low latitudes in the afternoon local time sector during the SSW, indicating significant cooling effects in the tropical upper thermosphere. Copyright © 2011 by the American Geophysical Union.

    DOI: 10.1029/2011JA016607

    Scopus

  307. Ionospheric disturbances detected by GPS total electron content observation after the 2011 off the Pacific coast of Tohoku Earthquake 査読有り

    Tsugawa, T; Saito, A; Otsuka, Y; Nishioka, M; Maruyama, T; Kato, H; Nagatsuma, T; Murata, KT

    EARTH PLANETS AND SPACE   63 巻 ( 7 ) 頁: 875 - 879   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.035

    Web of Science

  308. Numerical simulations of atmospheric waves excited by the 2011 off the Pacific coast of Tohoku Earthquake 査読有り

    Matsumura, M; Saito, A; Iyemori, T; Shinagawa, H; Tsugawa, T; Otsuka, Y; Nishioka, M; Chen, CH

    EARTH PLANETS AND SPACE   63 巻 ( 7 ) 頁: 885 - 889   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.07.015

    Web of Science

  309. New aspects of thermospheric and ionospheric storms revealed by CHAMP 査読有り

    N. Balan, M. Yamamoto, J. Y. Liu, Y. Otsuka, H. Liu, H. Lühr

    Journal of Geophysical Research: Space Physics   116 巻 ( 7 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    The neutral mass density N and electron density Ne at 400 km height measured by CHAMP during nine intense geomagnetic storms bring out some new aspects of the thermospheric and ionospheric storms. The thermospheric storms (increase of N) develop with the onset of the main phases (MP) of the geomagnetic storms and reach their peak phases before or by the end of the MPs. The ionospheric storms (change of Ne) in general undergo an initial negative phase (with the equatorial ionization anomaly (EIA) crests shifting poleward) before turning positive, and the positive storms reach their peak strengths (or phases) centered at 25-30 magnetic latitudes
    in some (4) cases the positive storms develop without an initial negative phase and with the EIA crests shifting equatorward
    in all cases the positive storms reach their peak phases before the end of the MPs and turn to conventional negative storms by the end of the MPs. The observations agree with the different aspects of a physical mechanism of the positive storms. The observations also reveal that the Halloween storms of 30 October 2003 with a short MP without fluctuations produced the strongest positive ionospheric storms through impulsive response, and there is strong equinoctial asymmetry in the ionosphere and thermosphere during geomagnetic storms. Copyright 2011 by the American Geophysical Union.

    DOI: 10.1029/2010JA016399

    Scopus

  310. Motion of polar cap arcs 査読有り

    Hosokawa, K, J. I. Moen, K. Shiokawa, Y. Otsuka

    Journal of Geophysical Research   116 巻   頁: doi:10.1029/2010JA015906   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  311. Long-distance propagation of ionospheric disturbance generated by the 2011 off the Pacific coast of Tohoku Earthquake 査読有り

    Chen, CH; Saito, A; Lin, CH; Liu, JY; Tsai, HF; Tsugawa, T; Otsuka, Y; Nishioka, M; Matsumura, M

    EARTH PLANETS AND SPACE   63 巻 ( 7 ) 頁: 881 - 884   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.026

    Web of Science

  312. ISS-IMAPミッションによって明らかになる超高層大気の姿

    斎藤昭則, 山崎敦, 阿部琢美, 鈴木睦, 坂野井健, 藤原均, 吉川一朗, 大塚雄一, 田口真, 山本衛, 中村卓司, 江尻省, 菊池雅行, 河野英昭, 石井守, 久保田実, 星野尾一明, 坂野井和代

    第25回大気圏シンポジウム     2011年

     詳細を見る

    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  313. Ionospheric multiple stratifications and irregularities induced by the 2011 off the Pacific coast of Tohoku Earthquake 査読有り

    Maruyama, T; Tsugawa, T; Kato, H; Saito, A; Otsuka, Y; Nishioka, M

    EARTH PLANETS AND SPACE   63 巻 ( 7 ) 頁: 869 - 873   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.008

    Web of Science

  314. On postmidnight low-latitude ionospheric irregularities during solar minimum: 1. Equatorial Atmosphere Radar and GPS-TEC observations in Indonesia 査読有り

    T. Yokoyama, M. Yamamoto, Y. Otsuka, M. Nishioka, T. Tsugawa, S. Watanabe, R. F. Pfaff

    Journal of Geophysical Research: Space Physics   116 巻 ( 11 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    Using the 47 MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (10.36S dip latitude), it is shown that postmidnight irregularities during solar minimum are morphologically different from those detected during solar maximum and are quite similar to those observed with the middle and upper atmosphere (MU) radar in midlatitudes (29.3N dip latitude). Utilizing the rapid beam-steering capability of the EAR, the spatial structure of the postmidnight irregularities is clearly presented for the first time. It is found that they usually propagate westward and can be categorized into two types. One shows sharp upwelling plumes near local midnight, which should not be a mere passage of fossil plasma bubbles. The other has successive tilted structures which have the same orientation as medium-scale traveling ionospheric disturbances typically observed at midlatitudes. We suggest that the convergence of the equatorward thermospheric wind which is believed to be responsible for the midnight temperature maximum may be an important factor to produce a preferable condition for the upwelling plumes in the postmidnight sector. The displacement between geographic and magnetic equators may also be important for seasonal/longitudinal variation of the postmidnight irregularities. © 2011 by the American Geophysical Union.

    DOI: 10.1029/2011JA016797

    Scopus

  315. Propagation of large amplitude ionospheric disturbances with velocity dispersion observed by the SuperDARN Hokkaido radar after the 2011 off the Pacific coast of Tohoku Earthquake 査読有り

    Nishitani, N; Ogawa, T; Otsuka, Y; Hosokawa, K; Hori, T

    EARTH PLANETS AND SPACE   63 巻 ( 7 ) 頁: 891 - 896   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.07.003

    Web of Science

  316. On postmidnight low-latitude ionospheric irregularities during solar minimum: 2. C/NOFS observations and comparisons with the Equatorial Atmosphere Radar 査読有り

    T. Yokoyama, R. F. Pfaff, P. A. Roddy, M. Yamamoto, Y. Otsuka

    Journal of Geophysical Research: Space Physics   116 巻 ( 11 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    A detailed comparison between the observations of the Communication/ Navigation Outage Forecasting System (C/NOFS) satellite and the 47 MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (10.36S dip latitude) on the postmidnight irregularities is presented. The zonal and meridional E × B drift velocities measured by the vector electric field instrument on the C/NOFS are consistent with the westward propagation of backscatter echoes and the line-of-sight Doppler velocities observed with the EAR, respectively. The plasma density depletions are observed in the postmidnight sector for several consecutive orbits, which suggests the depletions grow slowly during the premidnight period and reach the spacecraft altitude around local midnight. The convergence of the equatorward wind which could be responsible for the midnight temperature maximum may produce a preferable condition for the growth of the Rayleigh-Taylor instability around midnight. Electric field fluctuations of medium-scale traveling ionospheric disturbances may play an important role in seeding the instability. Both equatorial and midlatitude-type plasma instabilities could be operational at the EAR latitude sector, which together would foster a high occurrence of postmidnight irregularities during solar minimum. Copyright 2011 by the American Geophysical Union.

    DOI: 10.1029/2011JA016798

    Scopus

  317. Vertical connection from the tropospheric activities to the ionospheric longitudinal structure simulated by a new Earth's whole atmosphere-ionosphere coupled model 査読有り

    H. Jin, Y. Miyoshi, H. Fujiwara, H. Shinagawa, K. Terada, N. Terada, M. Ishii, Y. Otsuka, A. Saito

    Journal of Geophysical Research: Space Physics   116 巻 ( 1 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    This paper introduces a new Earth's atmosphere-ionosphere coupled model that treats seamlessly the neutral atmospheric region from the troposphere to the thermosphere as well as the thermosphere-ionosphere interaction including the electrodynamics self-consistently. The model is especially useful for the study of vertical connection between the meteorological phenomena and the upper atmospheric behaviors. As an initial simulation using the coupled model, we have carried out a 30 day consecutive run in September. The result reveals that the longitudinal structure of the F-region ionosphere varies on a day-to-day basis in a highly complex way and that a four-peak structure of the daytime equatorial ionization anomaly (EIA) similar to the recent observations appears as an averaged feature. The simulation reproduces and thus confirms the vertical coupling processes proposed so far with respect to the formation of the averaged EIA longitudinal structure
    the excitation of solar nonmigrating tides in the troposphere, their propagation through the middle atmosphere, and the modulation of ionospheric dynamo, which in turn affects EIA generation. The simulation result indicates that not only the ionospheric averaged longitudinal structure but also the day-to-day variation can be modulated significantly by the lower atmospheric effect. Copyright 2011 by the American Geophysical Union.

    DOI: 10.1029/2010JA015925

    Scopus

  318. Dynamic temporal evolution of polar cap tongue of ionization during magnetic storm 査読有り

    K. Hosokawa, T. Tsugawa, K. Shiokawa, Y. Otsuka, N. Nishitani, T. Ogawa, M. R. Hairston

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    During a magnetic storm on 14-16 December 2006, a polar cap tongue of ionization (TOI) was detected by an all-sky imager (ASI) at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E). We investigate the temporal evolution and spatial structure of the TOI in detail by combining the optical data with other observations (e. g., solar wind, GPS total electron content, SuperDARN, and DMSP and NOAA POES satellites). The TOI was observed as a bright and elongated 630 nm airglow plume for 4 h during the main phase of the storm. This interval corresponded to a period of prolonged stable large-amplitude southward IMF during a coronal mass ejection (CME). One to one and a half hours before the appearance of TOI, the polar cap boundary expanded rapidly far equatorward, and a positive ionospheric storm occurred. This implies that both the "expansion of the high-latitude plasma convection" and "build up of the source plasma in the midlatitudes" are necessary conditions for the formation of a TOI. Because both of them were triggered by a major southward turning of the IMF, the prolonged large-amplitude southward IMF orientation in the trailing part of the CME was primarily responsible for the generation of TOI. After its appearance, the TOI exhibited dynamic motion in the dawn to dusk direction. Simultaneous SuperDARN data suggest that a longitudinal progression of subauroral polarization stream controlled this dynamic motion. The optical TOI was found to be a continuous stream elongated in the noon-midnight direction although it contained some mesoscale patterns. Absence of large-scale temporal changes in the cusp plasma flow during the stable IMF period allowed the TOI to remain continuous without being broken into polar cap patches. The mesoscale structures within the TOI were probably produced by small-scale velocity fluctuations in the cusp plasma flow. The TOI as visualized with the all-sky airglow imager was found to be much more dynamic and much more complicated than we ever thought. The current study indicates that such a behavior of the TOI was presumably caused by a combination of temporal variations in the global-scale plasma circulation system, expansion and contraction of the polar cap area, and plasma density changes in the dayside low to midlatitudes.

    DOI: 10.1029/2010JA015848

    Web of Science

  319. Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL 査読有り

    Toru Adachi, Masashi Yamaoka, Mamoru Yamamoto, Yuichi Otsuka, Huixin Liu, Chun-Chieh Hsiao, Alfred B. Chen, Rue-Ron Hsu

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) payload on board the FORMOSAT-2 satellite carried out the first limb imaging observation of 630 nm airglow for the purpose of studying physical processes in the F region ionosphere. For a total of 14 nights in 2006-2008, ISUAL scanned the midnight latitude-altitude distribution of 630 nm airglow in the Asian sector. On two nights of relatively active conditions (Sigma Kp = 26, 30+) we found several bright airglow regions, which were highly variable each night in terms of luminosity and location. In relatively quiet conditions (Sigma Kp = 4-20) near May/June we found two bright regions which were stably located in the midlatitude region of 40 degrees S-10 degrees S (50 degrees S-20 degrees S magnetic latitude (MLAT)) and in the equatorial region of 0 degrees-10 degrees N (10 degrees S-0 degrees MLAT). On one of the quiet nights, FORMOSAT-3/COSMIC and CHAMP simultaneously measured the plasma density in the same region where ISUAL observed airglow. The plasma density data generally show good agreement, suggesting that plasma enhancements were the primary source of these two bright airglow regions. From detailed comparison with past studies we explain that the airglow in the equatorial region was due to the midnight brightness wave produced in association with the midnight temperature maximum, while that in the midlatitude region was due to the typical plasma distribution usually formed in the midnight sector. The fact that the equatorial airglow was much brighter than the midlatitude airglow and was observed on most nights during the campaign period strongly suggests the importance of further studies on the MTM/MBW phenomenology, which is not well reproduced in the current general circulation model.

    DOI: 10.1029/2009JA015147

    Web of Science

  320. Large-scale traveling ionospheric disturbance observed by superDARN Hokkaido HF radar and GPS networks on 15 December 2006 査読有り

    Hayashi, H, Nishitani, N, Ogawa, T, Otsuka, Y, Tsugawa, T, Hosokawa, K, Saito, A

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年6月

     詳細を見る

  321. Large-scale traveling ionospheric disturbance observed by superDARN Hokkaido HF radar and GPS networks on 15 December 2006 査読有り

    H. Hayashi, N. Nishitani, T. Ogawa, Y. Otsuka, T. Tsugawa, K. Hosokawa, A. Saito

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    On 15 December 2006, during the main phase of a relatively large storm, Doppler velocity data from the Super Dual Aural Radar Network (SuperDARN) Hokkaido radar, together with total electron content (TEC) data from the GPS Earth Observation Network (GEONET), recorded daytime large-scale traveling ionospheric disturbances (LSTIDs). We studied two disturbances propagating southward and one disturbance propagating northward between 0000 and 0600 UT on 15 December 2006. The former disturbances were LSTIDs typical of those reported in many previous studies, whereas the latter was confirmed as an LSTID propagating from the Southern into the Northern Hemisphere, reported in a few past studies. From comparisons of SuperDARN Hokkaido radar Doppler velocity and GEONET TEC, we found a positive correlation between downward ionospheric motion and increasing TEC. This relationship is consistent with results of model calculation. This is the first observation of LSTIDs ranging from high to low latitude combining simultaneous SuperDARN HF radar and GPS network observations.

    DOI: 10.1029/2009JA014297

    Web of Science

  322. Nighttime-like quasi periodic echoes induced by a partial solar eclipse 査読有り

    Thampi, SV; Yamamoto, M; Liu, HX; Saito, S; Otsuka, Y; Patra, AK

    GEOPHYSICAL RESEARCH LETTERS   37 巻   2010年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010GL042855

    Web of Science

  323. Longitudinal development of low-latitude ionospheric irregularities during the geomagnetic storms of July 2004 査読有り

    Li, GZ; Ning, BQ; Hu, LH; Liu, LB; Yue, XA; Wan, WX; Zhao, BQ; Igarashi, K; Kubota, M; Otsuka, Y; Xu, JS; Liu, JY

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 4 )   2010年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009JA014830

    Web of Science

    Scopus

  324. A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 査読有り

    Balan N, Shiokawa K, Otsuka Y, Kikuchi T, Lekshmi D. Vijaya, Kawamura S, Yamamoto M, Bailey G. J

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年2月

  325. Reorganization of polar cap patches through shears in the background plasma convection 査読有り

    K. Hosokawa, J. -P. St-Maurice, G. J. Sofko, K. Shiokawa, Y. Otsuka, T. Ogawa

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻   2010年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    On the night of December 20, 2006, 630 nm airglow images obtained by an all-sky camera at Resolute Bay, Canada (74.73 degrees N, 265.07 degrees E; altitude adjusted corrected geomagnetic (AACGM) latitude 82.9 degrees) showed the passage of successive polar cap patches. Shortly after convection came to a temporary halt, one of the patches was reorganized into two substructures in approximately 8 min. The two-dimensional background ionospheric convection pattern measured using the newly deployed PolarDARN radar at Rankin Inlet (62.82 degrees N, 93.11 degrees W; AACGM latitude 72.96 degrees) showed that a velocity shear of approximately 120 m s(-1)/340 km suddenly appeared in the vicinity of the patch at the time of reorganization. A qualitative analysis of the relationship between the magnitude of the velocity shear and the distance between the divided patches indicates that the shear in the background plasma convection velocity significantly contributed to the reorganization of the patch. This shear structure appeared soon after a southward turning of the interplanetary magnetic field (IMF) and was probably associated with the reconfiguration of the convection pattern from a pre-existing northward-oriented IMF pattern to a southward-oriented one. The present observations indicate that the reconfiguration/deformation of patches because of a shear in the background convection field, especially reorganization of patches into smaller substructures, may play an important role in the rapid structuring of patches.

    DOI: 10.1029/2009JA014599

    Web of Science

  326. A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 査読有り

    N. Balan, K. Shiokawa, Y. Otsuka, T. Kikuchi, D. Vijaya Lekshmi, S. Kawamura, M. Yamamoto, G. J. Bailey

    Journal of Geophysical Research: Space Physics   115 巻 ( 2 )   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    [1] A physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi-instrument observations, theoretical modeling, and basic principles. According to the mechanism, an equatorward neutral wind is required to produce positive ionospheric storms. The mechanical effects of the wind (1) reduce (or stop) the downward diffusion of plasma along the geomagnetic field lines, (2) raise the ionosphere to high altitudes of reduced chemical loss, and hence (3) accumulate the plasma at altitudes near and above the ionospheric peak centered at around ±30° magnetic latitudes. Daytime eastward prompt penetration electric field (PPEF), if it occurs, also shifts the equatorial ionization anomaly crests to higher than normal latitudes, up to approximately ±30° latitudes. The positive ionospheric storms are most likely in the longitudes where the onset of the geomagnetic storms falls in the ionization production dominated morning-noon local time sector when the plasma accumulation due to the mechanical effects of the wind largely exceeds the plasma loss due to the chemical effect of the wind. The mechanism agrees with the multi-instrument observations made during the supergeomagnetic storm of 7-8 November 2004, with 18 h long initial phase (IP) and 10 h long main phase (MP). The observations, which are mainly in the Japanese-Australian longitudes where the MP onset was in the morning (0600 LT, 2100 UT), show (1) strong positive ionospheric storms (in Ne, Nmax, hmax, Global Positioning System-total electron content (GPS-TEC), and 630 nm airglow intensity) in both Northern and Southern hemispheres started at the morning (0600 LT) MP onset and lasted for a day, (2) repeated occurrence of strong eastward PPEF events penetrated after the MP onset and superposed with westward electric field started before the MP onset, and (3) storm time equatorward neutral winds (inferred from 1 and 2). Repeated occurrence of an unusually strong F3 layer with large density depletions around the equator was also observed during the morning-noon MP. Copyright 2010 by the American Geophysical Union.

    DOI: 10.1029/2009JA014515

    Scopus

  327. Dynamic temporal evolution of polar cap tongue of ionization during magnetic storm 査読有り

    K. Hosokawa, T. Tsugawa, K. Shiokawa, Y. Otsuka, N. Nishitani, T. Ogawa, M. R. Hairston

    Journal of Geophysical Research: Space Physics   115 巻 ( 12 )   2010年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    During a magnetic storm on 14-16 December 2006, a polar cap tongue of ionization (TOI) was detected by an all-sky imager (ASI) at Resolute Bay, Canada (74.73°N, 265.07°E). We investigate the temporal evolution and spatial structure of the TOI in detail by combining the optical data with other observations (e.g., solar wind, GPS total electron content, SuperDARN, and DMSP and NOAA POES satellites). The TOI was observed as a bright and elongated 630 nm airglow plume for 4 h during the main phase of the storm. This interval corresponded to a period of prolonged stable large-amplitude southward IMF during a coronal mass ejection (CME). One to one and a half hours before the appearance of TOI, the polar cap boundary expanded rapidly far equatorward, and a positive ionospheric storm occurred. This implies that both the "expansion of the high-latitude plasma convection" and "build up of the source plasma in the midlatitudes" are necessary conditions for the formation of a TOI. Because both of them were triggered by a major southward turning of the IMF, the prolonged large-amplitude southward IMF orientation in the trailing part of the CME was primarily responsible for the generation of TOI. After its appearance, the TOI exhibited dynamic motion in the dawn to dusk direction. Simultaneous SuperDARN data suggest that a longitudinal progression of subauroral polarization stream controlled this dynamic motion. The optical TOI was found to be a continuous stream elongated in the noon-midnight direction although it contained some mesoscale patterns. Absence of large-scale temporal changes in the cusp plasma flow during the stable IMF period allowed the TOI to remain continuous without being broken into polar cap patches. The mesoscale structures within the TOI were probably produced by small-scale velocity fluctuations in the cusp plasma flow. The TOI as visualized with the all-sky airglow imager was found to be much more dynamic and much more complicated than we ever thought. The current study indicates that such a behavior of the TOI was presumably caused by a combination of temporal variations in the global-scale plasma circulation system, expansion and contraction of the polar cap area, and plasma density changes in the dayside low to midlatitudes. Copyright 2010 by the American Geophysical Union.

    DOI: 10.1029/2010JA015848

    Scopus

  328. Large-scale traveling ionospheric disturbance observed by superDARN Hokkaido HF radar and GPS networks on 15 December 2006 査読有り

    H. Hayashi, N. Nishitani, T. Ogawa, Y. Otsuka, T. Tsugawa, K. Hosokawa, A. Saito

    Journal of Geophysical Research: Space Physics   115 巻 ( 6 )   2010年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    On 15 December 2006, during the main phase of a relatively large storm, Doppler velocity data from the Super Dual Aural Radar Network (SuperDARN) Hokkaido radar, together with total electron content (TEC) data from the GPS Earth Observation Network (GEONET), recorded daytime large-scale traveling ionospheric disturbances (LSTIDs). We studied two disturbances propagating southward and one disturbance propagating northward between 0000 and 0600 UT on 15 December 2006. The former disturbances were LSTIDs typical of those reported in many previous studies, whereas the latter was confirmed as an LSTID propagating from the Southern into the Northern Hemisphere, reported in a few past studies. From comparisons of SuperDARN Hokkaido radar Doppler velocity and GEONET TEC, we found a positive correlation between downward ionospheric motion and increasing TEC. This relationship is consistent with results of model calculation. This is the first observation of LSTIDs ranging from high to low latitude combining simultaneous SuperDARN HF radar and GPS network observations. Copyright © 2010 by the American Geophysical Union.

    DOI: 10.1029/2009JA014297

    Scopus

  329. Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL 査読有り

    Toru Adachi, Masashi Yamaoka, Mamoru Yamamoto, Yuichi Otsuka, Huixin Liu, Chun-Chieh Hsiao, Alfred B. Chen, Rue-Ron Hsu

    Journal of Geophysical Research: Space Physics   115 巻 ( 9 )   2010年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) payload on board the FORMOSAT-2 satellite carried out the first limb imaging observation of 630 nm airglow for the purpose of studying physical processes in the F region ionosphere. For a total of 14 nights in 2006-2008, ISUAL scanned the midnight latitude-altitude distribution of 630 nm airglow in the Asian sector. On two nights of relatively active conditions (ΣKp = 26, 30+) we found several bright airglow regions, which were highly variable each night in terms of luminosity and location. In relatively quiet conditions (ΣKp = 4-20) near May/June we found two bright regions which were stably located in the midlatitude region of 40°S-10°S (50°S-20°S magnetic latitude (MLAT)) and in the equatorial region of 0°-10°N (10°S-0° MLAT). On one of the quiet nights, FORMOSAT-3/COSMIC and CHAMP simultaneously measured the plasma density in the same region where ISUAL observed airglow. The plasma density data generally show good agreement, suggesting that plasma enhancements were the primary source of these two bright airglow regions. From detailed comparison with past studies we explain that the airglow in the equatorial region was due to the midnight brightness wave produced in association with the midnight temperature maximum, while that in the midlatitude region was due to the typical plasma distribution usually formed in the midnight sector. The fact that the equatorial airglow was much brighter than the midlatitude airglow and was observed on most nights during the campaign period strongly suggests the importance of further studies on the MTM/MBW phenomenology, which is not well reproduced in the current general circulation model. Copyright 2010 by the American Geophysical Union.

    DOI: 10.1029/2009JA015147

    Scopus

  330. Lower-thermospheric wind fluctuations measured with an FPI during pulsating aurora at Tromso, Norway 査読有り

    Oyama, S; Shiokawa, K; Kurihara, J; Tsuda, TT; Nozawa, S; Ogawa, Y; Otsuka, Y; Watkins, BJ

    ANNALES GEOPHYSICAE   28 巻 ( 10 ) 頁: 1847 - 1857   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-28-1847-2010

    Web of Science

  331. Reorganization of polar cap patches through shears in the background plasma convection 査読有り

    K. Hosokawa, J. P. St-Maurice, G. J. Sofko, K. Shiokawa, Y. Otsuka, T. Ogawa

    Journal of Geophysical Research: Space Physics   115 巻 ( 1 )   2010年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    On the night of December 20, 2006, 630 nm airglow images obtained by an all-sky camera at Resolute Bay, Canada (74.73°N, 265.07°E
    altitude adjusted corrected geomagnetic (AACGM) latitude 82.9°) showed the passage of successive polar cap patches. Shortly after convection came to a temporary halt, one of the patches was reorganized into two substructures in approximately 8 min. The two-dimensional background ionospheric convection pattern measured using the newly deployed PolarDARN radar at Rankin Inlet (62.82°N, 93.11°W
    AACGM latitude 72.96°) showed that a velocity shear of approximately 120 m s-1/340 km suddenly appeared in the vicinity of the patch at the time of reorganization. A qualitative analysis of the relationship between the magnitude of the velocity shear and the distance between the divided patches indicates that the shear in the background plasma convection velocity significantly contributed to the reorganization of the patch. This shear structure appeared soon after a southward turning of the interplanetary magnetic field (IMF) and was probably associated with the reconfiguration of the convection pattern from a pre-existing northward-oriented IMF pattern to a southward-oriented one. The present observations indicate that the reconfiguration/deformation of patches because of a shear in the background convection field, especially reorganization of patches into smaller substructures, may play an important role in the rapid structuring of patches. Copyright 2010 by the American Geophysical Union.

    DOI: 10.1029/2009JA014599

    Scopus

  332. The STEL induction magnetometer network for observation of high-frequency geomagnetic pulsations 査読有り

    Shiokawa, K; Nomura, R; Sakaguchi, K; Otsuka, Y; Hamaguchi, Y; Satoh, M; Katoh, Y; Yamamoto, Y; Shevtsov, BM; Smirnov, S; Poddelsky, I; Connors, M

    EARTH PLANETS AND SPACE   62 巻 ( 6 ) 頁: 517 - 524   2010年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2010.05.003

    Web of Science

  333. 国際宇宙ステーションJEM曝露部からの超高層大気撮像観測計画ISS-IMAP

    齊藤昭則, 阿部琢美, 山崎敦, 鈴木睦, 坂野井健, 藤原均, 吉川一朗, 大塚雄一, 田口真, 山本衛, 中村卓司, 菊池雅行, 江尻省, 河野英昭, 石井守, 久保田実, 星野尾一明, 坂野井和代

    第10回宇宙科学シンポジウム講演集     2010年

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  334. Thermospheric temperature and density variations 査読有り

    Fujiwara, H; Miyoshi, Y; Jin, H; Shinagawa, H; Otsuka, Y; Saito, A; Ishii, M

    SOLAR AND STELLAR VARIABILITY: IMPACT ON EARTH AND PLANETS   ( 264 ) 頁: 310 - +   2010年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    DOI: 10.1017/S1743921309992857

    Web of Science

  335. Ionospheric and geomagnetic disturbances during the 2005 Sumatran earthquakes 査読有り

    Hasbi, AM; Momani, MA; Ali, MAM; Misran, N; Shiokawa, K; Otsuka, Y; Yumoto, K

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   71 巻 ( 17-18 ) 頁: 1992 - 2005   2009年12月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2009.09.004

    Web of Science

  336. On the gravity wave-driven instability of E layer at mid-latitude 査読有り

    Shalimov, S; Ogawa, T; Otsuka, Y

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   71 巻 ( 17-18 ) 頁: 1943 - 1947   2009年12月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2009.08.004

    Web of Science

  337. First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite 査読有り

    Thampi, SV; Yamamoto, M; Tsunoda, RT; Otsuka, Y; Tsugawa, T; Uemoto, J; Ishii, M

    GEOPHYSICAL RESEARCH LETTERS   36 巻   2009年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009GL039887

    Web of Science

  338. Coordinated observations of nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow and HF radar echoes at midlatitudes 査読有り

    Suzuki, S; Hosokawa, K; Otsuka, Y; Shiokawa, K; Ogawa, T; Nishitani, N; Shibata, TF; Koustov, AV; Shevtsov, BM

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   頁: A07312   2009年7月

  339. First simultaneous observations of daytime MSTIDs over North America using GPS-TEC and DEMETER satellite data 査読有り

    Onishi, T; Tsugawa, T; Otsuka, Y; Berthelier, JJ; Lebreton, JP

    GEOPHYSICAL RESEARCH LETTERS   36 巻   2009年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009GL038156

    Web of Science

  340. Spatial relationship of nighttime medium-scale traveling ionospheric disturbances and F region field-aligned irregularities observed with two spaced all-sky airglow imagers and the middle and upper atmosphere radar 査読有り

    Y. Otsuka, K. Shiokawa, T. Ogawa, T. Yokoyama, M. Yamamoto

    Journal of Geophysical Research: Space Physics   114 巻 ( 5 )   2009年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    We report simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) and field-aligned irregularities (FAls) in the F region using two all-sky airglow imagers and the middle and upper atmosphere (MU) radar. MSTIDs propagating southwestward were observed simultaneously in 630-nm airglow images over Sakata (39.0°N, 139.9°E) and Shigaraki (34.90N, 136.1°E), Japan, on the night of 16 June 2004. By using all-sky images over both sites, we estimated the altitude of the airglow layer to be 260 km by the triangulation method. During the MSTID event, FAIs in the F region were observed by making multibeam measurements with the MU radar at Shigaraki. In order to investigate the spatial relationship between the MSTIDs and FAIs, the FAIs were mapped onto the 630-nm airglow layer (altitude, 260 km) along the geomagnetic field lines. We found that FAIs with an intense (weak) signal-to-noise ratio coincided with the airglow depletion (enhancement) caused by the MSTIDs. FAI velocity obtained from a combination of the Doppler velocities on the three radar beams oscillated in the northwest-southeast direction, with an amplitude of approximately 82 m/s. The FAI velocity was northwestward (southeastward) at the airglow depletion (enhancement). The directions of the FAI velocity were consistent with those of the ExB drifts caused by the polarized electric fields associated with the MSTIDs. The northeastward polarized electric field at the airglow depletion region strengthened the background eastward effective electric field and drove the gradient drift instability generating FAIs. This might be the reason why the FAIs preferred to occur at the airglow depletion region. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013902

    Scopus

  341. Spatial relationship of nighttime medium-scale traveling ionospheric disturbances and F region field-aligned irregularities observed with two spaced all-sky airglow imagers and the middle and upper atmosphere radar 査読有り

    Y. Otsuka, K. Shiokawa, T. Ogawa, T. Yokoyama, M. Yamamoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We report simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) and field-aligned irregularities (FAIs) in the F region using two all-sky airglow imagers and the middle and upper atmosphere (MU) radar. MSTIDs propagating southwestward were observed simultaneously in 630-nm airglow images over Sakata (39.0 degrees N, 139.9 degrees E) and Shigaraki (34.9 degrees N, 136.1 degrees E), Japan, on the night of 16 June 2004. By using all-sky images over both sites, we estimated the altitude of the airglow layer to be 260 km by the triangulation method. During the MSTID event, FAIs in the F region were observed by making multibeam measurements with the MU radar at Shigaraki. In order to investigate the spatial relationship between the MSTIDs and FAIs, the FAIs were mapped onto the 630-nm airglow layer (altitude, 260 km) along the geomagnetic field lines. We found that FAIs with an intense (weak) signal-to-noise ratio coincided with the airglow depletion (enhancement) caused by the MSTIDs. FAI velocity obtained from a combination of the Doppler velocities on the three radar beams oscillated in the northwest-southeast direction, with an amplitude of approximately 82 m/s. The FAI velocity was northwestward (southeastward) at the airglow depletion (enhancement). The directions of the FAI velocity were consistent with those of the E x B drifts caused by the polarized electric fields associated with the MSTIDs. The northeastward polarized electric field at the airglow depletion region strengthened the background eastward effective electric field and drove the gradient drift instability generating FAIs. This might be the reason why the FAIs preferred to occur at the airglow depletion region.

    DOI: 10.1029/2008JA013902

    Web of Science

  342. Motion of polar cap patches: A statistical study with all-sky airglow imager at Resolute Bay, Canada 査読有り

    Hosokawa, K, Kashimoto, T, Suzuki, S, Shiokawa, K, Otsuka, Y, Ogawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年4月

     詳細を見る

  343. Motion of polar cap patches: A statistical study with all-sky airglow imager at Resolute Bay, Canada 査読有り

    Hosokawa K, Kashimoto T, Suzuki S, Shiokawa K, Otsuka Y, Ogawa T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年4月

  344. Unusually elongated, bright airglow plume in the polar cap F region: Is it a tongue of ionization? 査読有り

    Hosokawa, K; Tsugawa, T; Shiokawa, K; Otsuka, Y; Ogawa, T; Hairston, MR

    GEOPHYSICAL RESEARCH LETTERS   36 巻   2009年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009GL037512

    Web of Science

  345. Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities 査読有り

    Ogawa T, Nishitani N, Otsuka Y, Shiokawa K, Tsugawa T, Hosokawa K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

  346. Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities 査読有り

    T. Ogawa, N. Nishitani, Y. Otsuka, K. Shiokawa, T. Tsugawa, K. Hosokawa

    Journal of Geophysical Research: Space Physics   114 巻 ( 3 )   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    We present midlatitude medium-scale traveling ionospheric disturbances (MSTIDs) observed with a Super Dual Auroral Radar Network (SuperDARN) HF radar at around 10 MHz in Hokkaido, Japan, in combination with a 630-nm all-sky imager and a GPS network (GEONET) that provides total electron content (TEC) data. MSTIDs propagating southward from high latitudes are detected at first with the HF radar and then with the imager and GEONET. We analyze two MSTID events, one in winter (event 1) and the other in summer (event 2), to find that MSTIDs appear simultaneously, at least, at 55°-25°N. It is shown that nighttime MSTIDs propagate toward the southwest over a horizontal distance of about 4000 km, and daytime MSTIDs do so toward the southeast. Daytime radar echoes are due to ground/sea surface (GS) scatter, while nighttime echoes in event 1 return from 15-m-scale F region field-aligned irregularities (FAIs) and those in event 2 are due to GS scatter. Doppler velocities of the nighttime F region FAI echoes in event 1 are negative (motion away from the radar) within strong echo regions and are positive (motion toward the radar) within weak echo regions. This fact suggests that the strong (weak) echoes return from suppressed (enhanced) airglow/TEC areas, in line with previous observations over central Japan. The nighttime MSTIDs in events 1 and 2 are often accompanied by concurrent coherent echoes from FAIs in sporadic E (Es) layers. The Es echo areas in event 2 rather coincide with suppressed airglow/TEC areas in the F region that are connected with the echo areas along the geomagnetic field, indicating the existence of E and F region coupling at night. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013893

    Scopus

  347. Relationship between polar cap patches and field-aligned irregularities as observed with an all-sky airglow imager at Resolute Bay and the PolarDARN radar at Rankin Inlet 査読有り

    K. Hosokawa, K. Shiokawa, Y. Otsuka, T. Ogawa, J. P. St-Maurice, G. J. Sofko, D. A. Andre

    Journal of Geophysical Research: Space Physics   114 巻 ( 3 )   2009年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    Simultaneous two-dimensional observations of airglow enhancement and radar backscatter from field-aligned irregularities (FAIs) associated with polar cap patches were conducted. The spatial structure of 630 nm airglow from polar cap patches was imaged using an all-sky airglow imager at Resolute Bay, Canada, while backscatter echoes from decameter-scale FAIs were observed using the newly constructed HF Polar Dual Auroral Radar Network (PolarDARN) radar at Rankin Inlet, Canada. Both the airglow enhancement and the radar backscatter appeared within a structured region with the spatial extent of about 500-1000 km. The decameter-scale FAIs were found to extend over the entire region of airglow enhancement associated with polar cap patches, indicating that the polar patch plasma became almost fully structured soon after initiation (within approximately 2025 min). These findings imply that some rapid structuring process of the entire patch area is involved in addition to the primary gradient-drift instabilities. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013707

    Scopus

  348. Super plasma fountain and equatorial ionization anomaly during penetration electric field 査読有り

    N. Balan, K. Shiokawa, Y. Otsuka, S. Watanabe, G. J. Bailey

    Journal of Geophysical Research: Space Physics   114 巻 ( 3 )   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    Relative importance of diffusion, electric field, and neutral wind on equatorial plasma fountain and equatorial ionization anomaly (EIA) during a strong daytime eastward prompt penetration electric field (PPEF) event are evaluated using the Sheffield University Plasmasphere Ionosphere Model and the recorded PPEF during the super geomagnetic storm of 9 November 2004. The fountain rapidly develops into a super fountain during the PPEF event. The super fountain becomes strong with less poleward turning of the velocity vectors in the presence of an equatorward wind that reduces (or stops) the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss. The EIA crests in peak electron density and total electron content shift rapidly to higher than normal latitudes during the PPEF event. However, the crests become stronger than normal only in the presence of an equatorward wind. The results suggest that the presence of an equatorward neutral wind is required to produce a strong positive ionospheric storm during, a daytime eastward PPEF event. The equatorward neutral wind need not be a storm time wind though stronger wind can lead to stronger ionospheric storms. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013768

    Scopus

  349. Three-dimensional simulation of the coupled Perkins and es-layer instabilities in the nighttime midlatitude ionosphere 査読有り

    Tatsuhiro Yokoyama, David L. Hysell, Yuichi Otsuka, Mamoru Yamamoto

    Journal of Geophysical Research: Space Physics   114 巻 ( 3 )   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    Plasma density structures and associated irregularities in the nighttime midlatitude ionosphere are frequently observed as frontal structures elongated from northwest to southeast (NW-SE) in the Northern Hemisphere. The frontal structures and the coupling process between the E and F regions are studied with a three-dimensional numerical model, which can simulate two instability mechanisms: Perkins instability in the F-region and sporadic-E (E s)-layer instability in the E region. The fastest growth of the coupled instability occurs when the unstable conditions on NW-SE perturbation are satisfied in both regions. The perturbation of F-region integrated conductivity grows much faster than the isolated Perkins instability. The meridional component of a rotational wind shear blows an existing E5 layer southward, and the F-region structure follows the E-region drift velocity. The NW-SE structure in the E region can be formed from random perturbation regardless of the F-region condition. When the F region is unstable on the NW-SE perturbation, however, the NW-SE structure is formed in both regions with a common scale length. We conclude that (1) the Es-layer instability plays a major role in seeding NW-SE structure in the F region, and the Perkins instability is required to amplify its perturbation
    (2) the rotational wind shear in the E region produces southwestward phase propagation of the NW-SE structure in both the E and F regions
    and (3) the coupling process has a significant effect on the scale of the Es-layer perturbation rather than the growth rate of the Es-layer instability. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013789

    Scopus

  350. Relationship between polar cap patches and field-aligned irregularities as observed with an all-sky airglow imager at Resolute Bay and the PolarDARN radar at Rankin Inlet 査読有り

    K. Hosokawa, K. Shiokawa, Y. Otsuka, T. Ogawa, J. -P. St-Maurice, G. J. Sofko, D. A. Andre

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Simultaneous two-dimensional observations of airglow enhancement and radar backscatter from field-aligned irregularities (FAIs) associated with polar cap patches were conducted. The spatial structure of 630 nm airglow from polar cap patches was imaged using an all-sky airglow imager at Resolute Bay, Canada, while backscatter echoes from decameter-scale FAIs were observed using the newly constructed HF Polar Dual Auroral Radar Network (PolarDARN) radar at Rankin Inlet, Canada. Both the airglow enhancement and the radar backscatter appeared within a structured region with the spatial extent of about 500-1000 km. The decameter-scale FAIs were found to extend over the entire region of airglow enhancement associated with polar cap patches, indicating that the polar patch plasma became almost fully structured soon after initiation (within approximately 20-25 min). These findings imply that some rapid structuring process of the entire patch area is involved in addition to the primary gradient-drift instabilities.

    DOI: 10.1029/2008JA013707

    Web of Science

  351. Super plasma fountain and equatorial ionization anomaly during penetration electric field 査読有り

    N. Balan, K. Shiokawa, Y. Otsuka, S. Watanabe, G. J. Bailey

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Relative importance of diffusion, electric field, and neutral wind on equatorial plasma fountain and equatorial ionization anomaly (EIA) during a strong daytime eastward prompt penetration electric field (PPEF) event are evaluated using the Sheffield University Plasmasphere Ionosphere Model and the recorded PPEF during the super geomagnetic storm of 9 November 2004. The fountain rapidly develops into a super fountain during the PPEF event. The super fountain becomes strong with less poleward turning of the velocity vectors in the presence of an equatorward wind that reduces (or stops) the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss. The EIA crests in peak electron density and total electron content shift rapidly to higher than normal latitudes during the PPEF event. However, the crests become stronger than normal only in the presence of an equatorward wind. The results suggest that the presence of an equatorward neutral wind is required to produce a strong positive ionospheric storm during a daytime eastward PPEF event. The equatorward neutral wind need not be a storm time wind though stronger wind can lead to stronger ionospheric storms.

    DOI: 10.1029/2008JA013768

    Web of Science

  352. Three-dimensional simulation of the coupled Perkins and E-s-layer instabilities in the nighttime midlatitude ionosphere 査読有り

    Tatsuhiro Yokoyama, David L. Hysell, Yuichi Otsuka, Mamoru Yamamoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Plasma density structures and associated irregularities in the nighttime midlatitude ionosphere are frequently observed as frontal structures elongated from northwest to southeast (NW-SE) in the Northern Hemisphere. The frontal structures and the coupling process between the E and F regions are studied with a three-dimensional numerical model, which can simulate two instability mechanisms: Perkins instability in the F-region and sporadic-E (E-s)-layer instability in the E region. The fastest growth of the coupled instability occurs when the unstable conditions on NW-SE perturbation are satisfied in both regions. The perturbation of F-region integrated conductivity grows much faster than the isolated Perkins instability. The meridional component of a rotational wind shear blows an existing E-s layer southward, and the F-region structure follows the E-region drift velocity. The NW-SE structure in the E region can be formed from random perturbation regardless of the F-region condition. When the F region is unstable on the NW-SE perturbation, however, the NW-SE structure is formed in both regions with a common scale length. We conclude that (1) the E-s-layer instability plays a major role in seeding NW-SE structure in the F region, and the Perkins instability is required to amplify its perturbation; (2) the rotational wind shear in the E region produces southwestward phase propagation of the NW-SE structure in both the E and F regions; and (3) the coupling process has a significant effect on the scale of the E-s-layer perturbation rather than the growth rate of the E-s-layer instability.

    DOI: 10.1029/2008JA013789

    Web of Science

  353. Medium-Scale Traveling Ionospheric Disturbances and Plasma Bubbles Observed by an All-Sky Airglow Imager at Yonaguni, Japan 査読有り

    Ogawa, T; Otsuka, Y; Shiokawa, K; Tsugawa, T; Saito, A; Hoshinoo, K; Matunaga, K; Kubota, M; Ishii, M

    TERRESTRIAL ATMOSPHERIC AND OCEANIC SCIENCES   20 巻 ( 1 ) 頁: 287 - 295   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3319/TAO.2007.12.06.02(F3C)

    Web of Science

  354. Effects observed in the ionospheric F region in the east Asian sector during the intense geomagnetic disturbances in the early part of November 2004 査読有り

    Sahai Y., Becker-Guedes F., Fagundes P. R., de Jesus R., de Abreu A. J., Otsuka Y., Shiokawa K., Igarashi K., Yumoto K., Huang C. -S., Lan H. T., Saito A., Guarnieri F. L., Pillat V. G., Bittencourt J. A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻 ( 3 )   2009年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2008JA013053

    Web of Science

    Scopus

  355. Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations 査読有り

    S. Suzuki, K. Shiokawa, A. Z. Liu, Y. Otsuka, T. Ogawa, T. Nakamura

    ANNALES GEOPHYSICAE   27 巻 ( 4 ) 頁: 1625 - 1629   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:COPERNICUS GESELLSCHAFT MBH  

    We present the characteristics of small-scale (&lt; 100 km) gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3 degrees E, 0.2 degrees S), Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO) and the presence of many wave sources in the troposphere.

    DOI: 10.5194/angeo-27-1625-2009

    Web of Science

  356. Equatorial GPS ionospheric scintillations over Kototabang, Indonesia and their relation to atmospheric waves from below 査読有り

    Tadahiko Ogawa, Yasunobu Miyoshi, Yuichi Otsuka, Takuji Nakamura, Kazuo Shiokawa

    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 397 - 410   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    Using Global Positioning System (GPS) satellites. we have been conducting equatorial ionospheric scintillation observations at Kototabang, Indonesia since January 2003. Scintillations caused by equatorial plasma bubbles appear between 2000 and 0 100 LT in equinoctial months with a seasonal asymmetry, and their activity decreases with decreasing solar activity. A comparison between scintillation index (S-4) and Earth's brightness temperature variations suggests that file scintillation activity call be related to tropospheric disturbances over file Indian Ocean to the west of Kototabang. TO Understand better the reasons of day-to-day variability of S-4, we analyze S-4. T-bb and lower thermospheric neutral wind ((mu'(2)) over bar) data. The results show that S-4 fluctuates with periods of about 2.5, 5, 8, 14 and 25 days, possibly due to atmospheric waves from below and that similar periods are also found in the T-bb and (mu'(2)) over tilde variations. Using a general circulation model, we made numerical simulations to determine the behavior of neutral wind in the equatorial thermosphere. The results indicate the following: (1) 2- to 20-day waves dissipate rapidly above about an altitude of 125 km, and 0.5- to 3-hour waves become predominant above 100 km, (2) zonal winds above 200 km altitude are, on the whole, eastward during sunset-sunrise, (3) zonal wind patterns due to short-period (1-4 h) atmospheric gravity waves (AGWs) above 120 km altitude change day by day, exhibit wavy structures with scale lengths of about 30-1000 km and, as it whole, move eastward in about 100(-1) while changing patterns over time. These simulations suggest that the Rayleigh-Taylor instability responsible for plasma bubble generation call be seeded by AGWs with short periods of about 0.5-3 h, and that background conditions necessary for this instability are modulated by planetary-scale atmospheric waves propagating up to an altitude of about 120 km front below.

    DOI: 10.1186/BF03353157

    Web of Science

  357. Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 'Halloween Storms' 査読有り

    Sahai, Y; Becker-Guedes, F; Fagundes, PR; de Abreu, AJ; de Jesus, R; Pillat, VG; Abalde, JR; Martinis, CR; Brunini, C; Gende, M; Huang, CS; Pi, X; Lima, WLC; Bittencourt, JA; Otsuka, Y

    ANNALES GEOPHYSICAE   27 巻 ( 12 ) 頁: 4463 - 4477   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-27-4463-2009

    Web of Science

  358. Propagation characteristics of nighttime mesospheric and thermospheric waves observed by optical mesosphere thermosphere imagers at middle and low latitudes 査読有り

    K. Shiokawa, Y. Otsuka, T. Ogawa

    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 479 - 491   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER HEIDELBERG  

    We review measurements of nighttime atmospheric/ionospheric wave in the upper atmosphere in Japan. Indonesia. and Australia. using all-sky airglow imagers of optical mesosphere thermosphere imagers (OMTIs). The imagers observe two-dimensional patterns of airglow emissions from oxygen (wavelength: 557.7 nm) and hydorxyl (OH) (near-infrared band) in the mesopause region (80-100 km) and from oxygen (630.0 nm) in the thermosphere/ionosphere (200-300 km). Several statistical studies were done to investigate propagation characteristics of small-scale (less than 100 km) gravity waves in the mesopause region and medium-scale traveling ionospheric disturbances (MSTIDs. similar to 100-1,000 km) in the thermosphere/ionosphere. Clear seasonal variations of occurrence and propagation directions were reported for these waves. The propagation directions in the mesopause region are controlled by wind filtering, ducting processes and relative location to the wave sources in the troposphere. On the other hand, systematic equatorward and westward motions were observed for all seasons for nighttime MSTIDs in the midlatitude ionosphere with geomagnetic conjugacy between the northern and Southern hemispheres. Ionospheric instabilities may play important role for the generation and propagation of these MSTIDs. We also give an example of simultaneous observation of quasi-periodic southward-moving waves in the mesopause and in the thermosphere at the geographic equator, From these results, we discuss mean wind acceleration by mesospheric gravity waves and penetration of gravity waves from the mesosphere to the thermosphere.

    DOI: 10.1186/BF03353165

    Web of Science

  359. Relative effects of electric field and neutral wind on positive ionospheric storms 査読有り

    N. Balan, H. Alleyne, Y. Otsuka, D.Vijaya Lekshmi, B. G. Fejer, I. McCrea

    Earth, Planets and Space   61 巻 ( 4 ) 頁: 439 - 445   2009年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Springer Berlin  

    The paper studies the relative importance of penetrating eastward electric field (PEEF) and direct effects of equatorward neutral wind in leading to positive ionospheric storms at low-mid latitudes using observations and modeling. The observations show strong positive ionospheric storms in total electron content (TEC) and peak electron density (Nmax) at low-mid latitudes in Japan longitudes (≈125°E-145°E) during the first main phase (started at sunrise on 08 November) of a super double geomagnetic storm during 07-11 November 2004. The model results obtained using the Sheffield University Plasmashpere Ionosphere Model (SUPIM) show that the direct effects of storm-time equatorward neutral wind (that reduce poleward plasma flow and raise the ionosphere to high altitudes of reduced chemical loss) can be the main driver of positive ionospheric storms at low-mid latitudes except in Nmax around the equator. The equatorward wind without PEEF can also result in stronger positive ionospheric storms than with PEEF. Though PEEF on its own is unlikely to cause positive ionospheric storms, it can lead to positive ionospheric storms in the presence of an equatorward wind. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

    DOI: 10.1186/BF03353160

    Scopus

  360. The Optical Mesosphere Thermosphere Imagers (OMTIs) for network measurements of aurora and airglow 査読有り

    K. Shiokawa, K. Hosokawa, K. Sakaguchi, A. Ieda, Y. Otsuka, T. Ogawa, M. Connors

    FUTURE PERSPECTIVES OF SPACE PLASMA AND PARTICLE INSTRUMENTATION AND INTERNATIONAL COLLABORATIONS   1144 巻   頁: 212 - +   2009年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER INST PHYSICS  

    The Optical Mesosphere Thermosphere Imagers (OMTIs) currently consist of eight all-sky cooled-CCD imagers and several interferometers and spectrometers. They are making routine observations of aurora and airglow in Japan, Australia, Indonesia, and Canada. Here we show recent results of OMTIs particularly from. the two Canadian stations at Resolute Bay (RSB) and Athabasca (ATH). At RSB, we observe polar-cap plasma patches almost always during southward IMF periods. From two-dimensional cross-correlation analyses, we determine velocity vectors of the patches, which indicates the ionospheric convection vector, showing high correlation with the IMF-By and -Bz variations. At ATH, we often observe isolated proton arcs and Stable Auroral Red (SAR) arcs, which are located equatorward of the auroral oval. The appearance of the isolated proton arcs is highly correlated with the Pc I geomagnetic pulsations measured simultaneously at ATH, suggesting interactions between the electromagnetic ion cyclotron (EMIC) waves and protons in the vicinity of the plasmapause and the ring current. Similar interactions without waves are also suggested for the SAR arcs, which appear after the substorm expansion phase even without geomagnetic storms. These observations show promising capability to monitor magnetospheric processes from the ground stations, which would contribute to the future satellite projects, such as THEMIS, ERG, and Scope/Xscale.

    Web of Science

  361. Zonal asymmetry of daytime 150-km echoes observed by Equatorial Atmosphere Radar in Indonesia 査読有り

    T. Yokoyama, D. L. Hysell, A. K. Patra, Y. Otsuka, M. Yamamoto

    ANNALES GEOPHYSICAE   27 巻 ( 3 ) 頁: 967 - 974   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:COPERNICUS GESELLSCHAFT MBH  

    Multi-beam observations of the daytime ionospheric E-region irregularities and the so-called 150-km echoes with the 47-MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20 degrees S, 100.32 degrees E, 10.36 degrees S dip latitude) are presented. 150-km echoes have been frequently observed by the EAR, and their characteristics are basically the same as the equatorial ones, except for an intriguing zonal asymmetry; stronger echoes in lower altitudes in the east directions, and weaker echoes in higher altitudes in the west. The highest occurrence is seen at 5.7 degrees east with respect to the magnetic meridian, and the altitude gradually increases as viewing from the east to west. Arc structures which return backscatter echoes are proposed to explain the asymmetry. While the strength of radar echoes below 105 km is uniform within the wide coverage of azimuthal directions, the upper E-region (105-120 km) echoes also show a different type of zonal asymmetry, which should be generated by an essentially different mechanism from the lower E-region and 150-km echoes.

    DOI: 10.5194/angeo-27-967-2009

    Web of Science

  362. VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia 査読有り

    Y. Otsuka, T. Ogawa, Effendy

    EARTH PLANETS AND SPACE   61 巻 ( 4 ) 頁: 431 - 437   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    We report, for the first time, continuous observations of the nighttime F-region field-aligned irregularities (FAIs) over Indonesia. A VHF radar with operating frequency of 30.8 MHz and peak power of 20 kW has been operated at Kolotabang (0.20 degrees S, 100.32 degrees E; dip latitude 10.4 degrees S), Indonesia since February 2006. Five beams were allocated between +/- 54 degrees in azimuth around geographic South (126 degrees-234 degrees). From the Continuous observation from February 2006 to November 2007, we found that FAIs appeared frequently at pre-midnight between March and May and Lit post-midnight between May and August. The pre-midnight FAIs coincided well with GPS scintillation observed at the same site. Seasonal and local time variations of the pre-midnight FAI Occurrence are consistent with those of equatorial plasma bubbles reported in previous studies (e.g., Maruyama and Matuura, 1984). These results indicate that the pre-midnight FAIs could be associated with the equatorial plasma bubbles. On the other hand, seasonal and local time variations of the post-midnight FAIs were inconsistent with those of the plasma bubbles. The features of the post-midnight FAIs can be summarized as follows: (1) The post-midnight FAIs are not accompanied by GPS scintillations. (2) Most of the post-midnight FAI regions do not show propagation, but some of them propagate westward. (3) Echo intensity of the post-midnight FAIs was weaker than that of the pre-midnight FAIs. These features are similar to those of the FAI echoes that have been observed at mid-latitude (e.g., Fukao et, al., 1991). At Kototabang, Fukao et al. (2004) have firstly observed FAIs that resemble those Lit mid-latitude. The present paper reports statistical characteristics of the mid-latitude-type FAIs observed at Kototabang.

    DOI: 10.1186/BF03353159

    Web of Science

  363. Nighttime medium-scale traveling ionospheric disturbances detected by network GPS receivers in Taiwan 査読有り

    Lee, CC; Liou, YA; Otsuka, Y; Chu, FD; Yeh, TK; Hoshinoo, K; Matunaga, K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A12 )   2008年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2008JA013250

    Web of Science

  364. Northeastward motion of nighttime medium-scale traveling ionospheric disturbances at middle latitudes observed by an airglow imager

    Shiokawa, K; Otsuka, Y; Nishitani, N; Ogawa, T; Tsugawa, T; Maruyama, T; Smirnov, SE; Bychkov, VV; Shevtsov, BM

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A12 )   2008年12月

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    Nighttime medium-scale traveling ionospheric disturbances (MSTIDs) observed in 630-nm airglow images at middle latitudes are known to have a predominantly northwest-southeast phase surface and to move southwestward in the Northern Hemisphere of Earth. However, the mechanisms of MSTID generation and their systematic southwestward motion have not been clarified. In this paper, we report the &quot;northeastward&quot; motion of the MSTIDs observed at Paratunka, Far East Russia (52.97°N, 158.25°E), using an all-sky 630-nm airglow imager at 2000-2300 LT on 19 August 2007. The MSTIDs moved first southwestward but then back northeastward in the northern part of the images. The northeastward motion of the MSTIDs took place coincident with a F layer height decrease observed by an ionosonde at Paratunka. The F layer height decrease was also confirmed by an enhancement of the 630-nm airglow intensity, which seemed to propagate from northeast to southwest. This fact suggests that the F layer height decrease was caused by poleward wind enhancement rather than westward electric field. These observations imply that the F layer height decrease or the poleward thermospheric wind has some role in the northeastward turning of the MSTID propagation direction. Copyright 2008 by the American Geophysical Union.

    DOI: 10.1029/2008JA013417

    Web of Science

    Scopus

  365. Statistical study of relationship between medium-scale traveling ionospheric disturbance and sporadic E layer activities in summer night over Japan 査読有り

    Otsuka, Y., T. Tani, T. Tsugawa, and T. Ogawa

    J. Atmos. Solar-Terr. Phys.   70 巻   頁: 2196-2202   2008年12月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  366. Statistical study of relationship between medium-scale traveling ionospheric disturbance and sporadic E layer activities in summer night over Japan 査読有り

    Otsuka Y., Tani T., Tsugawa T., Ogawa T., Saito A.

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   70 巻 ( 17 ) 頁: 2196 - 2202   2008年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2008.07.008

    Web of Science

  367. Decay of 3-m-scale ionospheric irregularities associated with a plasma bubble observed with the Equatorial Atmosphere Radar 査読有り

    Saito, S; Fukao, S; Yamamoto, M; Otsuka, Y; Maruyama, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A11 )   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2008JA013118

    Web of Science

  368. F-3 layer during penetration electric field 査読有り

    Balan N., Thampi S. V., Lynn K., Otsuka Y., Alleyne H., Watanabe S., Abdu M. A., Fejer B. G.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻   2008年9月

  369. Simultaneous appearance of isolated auroral arcs and Pc 1 geomagnetic pulsations at subauroral latitudes 査読有り

    Sakaguchi, K; Shiokawa, K; Miyoshi, Y; Otsuka, Y; Ogawa, T; Asamura, K; Connors, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A5 )   2008年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007JA012888

    Web of Science

  370. Daytime 150-km echoes observed with the Equatorial Atmosphere Radar in Indonesia: First results 査読有り

    Patra, AK; Yokoyama, T; Otsuka, Y; Yamamoto, M

    GEOPHYSICAL RESEARCH LETTERS   35 巻 ( 6 )   2008年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007GL033130

    Web of Science

  371. First three-dimensional simulation of the Perkins instability in the nighttime midlatitude ionosphere 査読有り

    Yokoyama, T; Otsuka, Y; Ogawa, T; Yamamoto, M; Hysell, DL

    GEOPHYSICAL RESEARCH LETTERS   35 巻 ( 3 )   2008年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007GL032496

    Web of Science

  372. Optical and Radio Observations and AMIE/TIEGCM Modeling of Nighttime Traveling Ionospheric Disturbances at Midlatitudes During Geomagnetic Storms

    Shiokawa, K; Tsugawa, T; Otsuka, Y; Ogawa, T; Lu, G; Saito, A; Yamamoto, M

    MIDLATITUDE IONOSPHERIC DYNAMICS AND DISTURBANCES   181 巻   頁: 271 - 281   2008年

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    © 2008 by the American Geophysical Union. This paper summarizes our recent observations of storm-time traveling ionospheric disturbances (TIDs) over Japan. The storm-time TIDs, which are often referred as large-scale TIDs or traveling atmospheric disturbances, are generated at high-latitude auroral zone and propagate predominantly equatorward at midlatitudes as atmospheric waves in the thermosphere. The imaging measurements by airglow imagers and GPS networks give reliable wave parameters (wavelength, phase velocity, and amplitude) of TIDs. Comparison of imaging observations of TIDs between the northern and southern hemispheres revealed their nonconjugacy. Combinations of these imaging observations with vertical sounding measurements by ionosondes and radars provide a comprehensive description of TID structures at midlatitudes. Comparison between these observations and the assimilative mapping of the ionospheric electrodynamics technique with the thermosphere-ionosphere electrodynamics general circulation model results in several insights into the generation and propagation of TIDs at the high-latitude source region as well as limitations of the current global model.

    DOI: 10.1029/181GM24

    Web of Science

    Scopus

  373. Discovery of anoumoulous stripes over the amazon by the PALSAR onboard ALOS satellite 査読有り

    Masanobu Shimada, Yasushi Muraki, Yuichi Otsuka

    International Geoscience and Remote Sensing Symposium (IGARSS)   2 巻 ( 1 ) 頁: II387 - II390   2008年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    We discovered anomalous stripes over the large area of Amazon when the region was scanned by the radar (PALSAR) onboard ALOS satellite. The stripes appeared on the local midnight along the geomagnetic field line with a typical characteristic width of 600m. ©2008 IEEE.

    DOI: 10.1109/IGARSS.2008.4779009

    Scopus

  374. Medium-scale traveling ionospheric disturbances detected with dense and wide TEC maps over North America 査読有り

    Tsugawa, T; Otsuka, Y; Coster, AJ; Saito, A

    GEOPHYSICAL RESEARCH LETTERS   34 巻 ( 22 )   2007年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007GL031663

    Web of Science

  375. Summer-winter hemispheric asymmetry of the sudden increase in ionospheric total electron content and of the O/N-2 ratio: Solar activity dependence 査読有り

    Tsugawa T., Zhang S.-R., Coster A. J., Otsuka Y., Sato J., Saito A., Zhang Y., Paxton L. J.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A8 )   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007JA012415

    Web of Science

    Scopus

  376. Low-latitude total electron content enhancement at low geomagnetic activity observed over Japan 査読有り

    Kutiev, I; Otsuka, Y; Saito, A; Tsugawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A7 )   2007年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007JA012385

    Web of Science

  377. Simultaneous observations of nighttime medium-scale traveling ionospheric disturbances and E region field-aligned irregularities at midlatitude 査読有り

    Otsuka Y., Onoma F., Shiokawa K., Ogawa T., Yamamoto M., Fukao S.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A6 )   2007年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JA011548

    Web of Science

  378. Ground observation and AMIE-TIEGCM modeling of a storm-time traveling ionospheric disturbance 査読有り

    Shiokawa, K; Lu, G; Otsuka, Y; Ogawa, T; Yamamoto, M; Nishitani, N; Sato, N

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A5 )   2007年5月

  379. Simultaneous ground and satellite observations of an isolated proton arc at subauroral latitudes 査読有り

    Sakaguchi, K; Shiokawa, K; Ieda, A; Miyoshi, Y; Otsuka, Y; Ogawa, T; Connors, M; Donovan, EF; Rich, FJ

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A4 )   2007年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2006JA012135

    Web of Science

  380. An intense gravity wave near the mesopause region observed by a Fabry-Perot interferometer and an airglow imager 査読有り

    Shiokawa K., Suzuki S., Otsuka Y., Ogawa T., Nakamura T., Horinouchi T.

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   112 巻 ( D7 )   2007年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2006JD007385

    Web of Science

  381. Medium-scale traveling ionospheric disturbances observed by GPS receiver network in Japan: a short review 査読有り

    Tsugawa, T; Kotake, N; Otsuka, Y; Saito, A

    GPS SOLUTIONS   11 巻 ( 2 ) 頁: 139 - 144   2007年3月

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    記述言語:英語  

    DOI: 10.1007/s10291-006-0045-5

    Web of Science

  382. A concentric gravity wave structure in the mesospheric airglow images 査読有り

    Suzuki S., Shiokawa K., Otsuka Y., Ogawa T., Nakamura K., Nakamura T.

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   112 巻 ( D2 )   2007年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JD006558

    Web of Science

  383. Simultaneous observations of nighttime medium-scale traveling ionospheric disturbances and E-region field-aligned irregularities at midlatitude 査読有り

    Otsuka, Y., F. Onoma, K. Shiokawa, T. Ogawa, M. Yamamoto, and S. Fukao

    J. Geophys. Res     頁: doi:10.1029/2005JA011548   2007年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  384. Statistical study of medium-scale traveling ionospheric disturbances observed with the GPS networks in Southern California 査読有り

    Kotake, N; Otsuka, Y; Ogawa, T; Tsugawa, T; Saito, A

    EARTH PLANETS AND SPACE   59 巻 ( 2 ) 頁: 95 - 102   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352681

    Web of Science

  385. The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003 査読有り

    Becker-Guedes, F; Sahai, Y; Fagundes, PR; Espinoza, ES; Pillat, VG; Lima, WLC; Basu, S; Basu, S; Otsuka, Y; Shiokawa, K; MacKenzie, EM; Pi, X; Bittencourt, JA

    ANNALES GEOPHYSICAE   25 巻 ( 4 ) 頁: 863 - 873   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-25-863-2007

    Web of Science

  386. Response of nighttime equatorial and low latitude F-region to the geomagnetic storm of August 18, 2003, in the Brazilian sector 査読有り

    Sahai, Y; Becker-Guedes, F; Fagundes, PR; Lima, WLC; Otsuka, Y; Huang, CS; Espinoza, ES; Pi, X; de Abreu, AJ; Bolzan, MJA; Pillat, VG; Abalde, JR; Pimenta, AA; Bittencourt, JA

    ADVANCES IN SPACE RESEARCH   39 巻 ( 8 ) 頁: 1325 - 1334   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.asr.2007.02.064

    Web of Science

  387. Development of airglow temperature photometers with cooled-CCD detectors 査読有り

    Shiokawa, K; Otsuka, Y; Suzuki, S; Katoh, T; Katohl, Y; Satoh, M; Ogawa, T; Takahashi, H; Gobbli, D; Nakamura, T; Williams, BP; She, CY; Taguchi, M; Shimomai, T

    EARTH PLANETS AND SPACE   59 巻 ( 6 ) 頁: 585 - 599   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352721

    Web of Science

  388. Gravity wave momentum flux in the upper mesosphere derived from OH airglow imaging measurements 査読有り

    Suzuki, S; Shiokawa, K; Otsuka, Y; Ogawa, T; Kubota, M; Tsutsumi, M; Nakamura, T; Fritts, DC

    EARTH PLANETS AND SPACE   59 巻 ( 5 ) 頁: 421 - 428   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352703

    Web of Science

  389. Summer-winter hemispheric asymmetry of sudden increase in ionospheric total electron content induced by solar flares: A role of O/N-2 ratio 査読有り

    Tsugawa T., Sadakane T., Sato J., Otsuka Y., Ogawa T., Shiokawa K., Saito A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A11 )   2006年11月

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    記述言語:英語  

    DOI: 10.1029/2006JA011951

    Web of Science

  390. A fast-propagating, large-scale atmospheric gravity wave observed in the WAVE2004 campaign 査読有り

    Kubota, M; Kawamura, S; Abo, M; Koizumi, Y; Murayama, Y; Yamamori, M; Shiokawa, K; Otsuka, Y; Uchiumi, M; Igarashi, K; Abe, T; Oyama, KI; Iwagami, N

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   111 巻 ( D21 )   2006年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JD006788

    Web of Science

  391. Detection of ruptures of Andaman fault segments in the 2004 great Sumatra earthquake with coseismic ionospheric disturbances 査読有り

    Heki, K; Otsuka, Y; Choosakul, N; Hemmakorn, N; Komolmis, T; Maruyama, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH   111 巻 ( B9 )   2006年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JB004202

    Web of Science

    Scopus

  392. Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada 査読有り

    Hosokawa, K; Shiokawa, K; Otsuka, Y; Nakajima, A; Ogawa, T; Kelly, JD

    GEOPHYSICAL RESEARCH LETTERS   33 巻 ( 15 )   2006年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2006GL026916

    Web of Science

  393. A multi-instrument measurement of a mesospheric front-like structure at the equator 査読有り

    Shiokawa, K; Suzuki, S; Otsuka, Y; Ogawa, T; Nakamura, T; Mlynczak, MG; Russell, JM

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   84A 巻   頁: 305 - 316   2006年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2151/jmsj.84A.305

    Web of Science

  394. Equatorial ionospheric scintillations and zonal irregularity drifts observed with closely-spaced GPS receivers in Indonesia 査読有り

    Otsuka, Y; Shiokawa, K; Ogawa, T

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   84A 巻   頁: 343 - 351   2006年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2151/jmsj.84A.343

    Web of Science

  395. Ionospheric disturbances over Indonesia and their possible association with atmospheric gravity waves from the troposphere 査読有り

    Ogawa, T; Otsuka, Y; Shiokawa, K; Saito, A; Nishioka, M

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   84A 巻   頁: 327 - 342   2006年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2151/jmsj.84A.327

    Web of Science

  396. Quasiperiodic southward moving waves in 630-nm airglow images in the equatorial thermosphere 査読有り

    Shiokawa, K; Otsuka, Y; Ogawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A6 )   2006年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JA011406

    Web of Science

  397. Characteristics and implications of Doppler spectra of E region quasi-periodic echoes observed by the multibeam middle and upper atmosphere radar 査読有り

    Ogawa Tadahiko, Otsuka Yuichi, Yamamoto Mamoru

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A5 )   2006年5月

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    記述言語:日本語  

    DOI: 10.1029/2005JA011335

    Web of Science

  398. Climatological study of GPS total electron content variations caused by medium-scale traveling ionospheric disturbances 査読有り

    Kotake, N; Otsuka, Y; Tsugawa, T; Ogawa, T; Saito, A

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A4 )   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JA011418

    Web of Science

  399. Geomagnetic conjugate observations of large-scale traveling ionospheric disturbances using GPS networks in Japan and Australia 査読有り

    Tsugawa, T; Shiokawa, K; Otsuka, Y; Ogawa, T; Saito, A; Nishioka, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A2 )   2006年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JA011300

    Web of Science

  400. Equatorial ionospheric scintillations and zonal irregularity drifts observed with closely-spaced GPS receivers in Indonesia 査読有り

    Otsuka, Y., K. Shiokawa, and T. Ogawa

    J. Meteor. Soc. Japan   84A 巻   頁: 343-351   2006年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  401. A statistical study of ionospheric irregularities observed with a GPS network in Japan

    Otsuka, Y; Aramaki, T; Ogawa, T; Saito, A

    RECURRENT MAGNETIC STORMS: COROTATING SOLAR WIND STREAMS   167 巻   頁: 271 - +   2006年

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    © 2006 by the American Geophysical Union. All rights reserved. The Geographical Survey Institute of Japan has installed a network of about 1000 dual-frequency GPS receivers in Japan with their mutual distance of about 25 km. Phases and pseudo ranges of dual-frequency GPS signals are recorded every 30 s. The dense distribution of the GPS receivers allows us to reveal twodimensional structures of the ionospheric plasma density irregularities with scale sizes of the order of several kilometers. We analyzed TEC data obtained from the GPS network of Japan in 2000. It was found that the irregularity characteristics over Japan depended on latitude. The results are as follows: (1) at the northern part, the irregularities appeared only during geomagnetic storms. (2) At the middle part, they had the most frequent occurrence in summer nighttime and were usually accompanied by Medium-Scale Traveling Ionospheric Disturbances (MSTID). (3) At the southern part, they were associated with the equatorial plasma bubbles and their occurrences were highest in the equinoctial nighttime.

    DOI: 10.1029/167GM21

    Web of Science

    Scopus

  402. GPS observations of post-storm TEC enhancements at low latitudes 査読有り

    Kutiev, I; Otsuka, Y; Saito, A; Watanabe, S

    EARTH PLANETS AND SPACE   58 巻 ( 11 ) 頁: 1479 - 1486   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352647

    Web of Science

  403. GPS detection of total electron content variations over Indonesia and Thailand following the 26 December 2004 earthquake 査読有り

    Otsuka, Y; Kotake, N; Tsugawa, T; Shiokawa, K; Ogawa, T; Effendy; Saito, S; Kawamura, M; Maruyama, T; Hemmakorn, N; Komolmis, T

    EARTH PLANETS AND SPACE   58 巻 ( 2 ) 頁: 159 - 165   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences  

    We report the response of the ionosphere to the large earthquake that occurred in West Sumatra, Indonesia, at 0058 UT on December 26, 2004. We have analyzed Global Positioning System (GPS) data obtained at two sites in Sumatra and at three sites in Thailand to investigate total electron content (TEC) variations. Between 14 and 40 min after the earthquake, TEC enhancements of 1.6-6.9 TEC units (TECU) were observed at subionospheric points located 360-2000 km north of the epicenter. From the time delays of the observed TEC enhancements, we find that the TEC enhancements propagated northward from the epicenter. The time delays between the earthquake and rapid increases in TEC, which occurred near the epicenter, are consistent with the idea that acoustic waves generated by the earthquake propagated into the ionosphere at the speed of sound to cause the TEC variations. A small TEC enhancement of 0.6 TECU was observed south of the epicenter, while no TEC enhancements were seen east of the epicenter. From a model calculation, we find that this directivity of the TEC variations with respect to the azimuth from the epicenter could be caused partially by the directivity in the response of the electron density variation to the acoustic waves in the neutral atmosphere. © 2006, The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan, The Geodetic Society of Japan, The Japanese Society for Planetary Sciences. All rights reserved.

    DOI: 10.1186/BF03353373

    Web of Science

    Scopus

  404. Ionospheric variations at midlatitude detected by a dense GPS receiver array in Japan 査読有り

    A. Saito, Y. Otsuka, T. Tsugawa, K. Matsunaga, K. Hoshinoo

    Proceedings of the Annual Meeting - Institute of Navigation     頁: 425 - 428   2005年12月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Ionospheric variations over Japan were investigated with high spatial and temporal resolution data of GEONET, which consists of about 1,200 GPS receivers. Total Electron Content (TEC) data derived from GEONET clarified that various ionospheric phenomena cause the variation of the ionosphere in the region around 30 degrees of the geomagnetic latitude, and affect on the navigation system. The large day-to-day variation of TEC gradient over Japan was found to be attributed to the day-to-day variation of the Equatorial Ionization Anomaly (EIA) because Japan is located on the northern slope of EIA. The amplitude and location of EIA have large variability because they are controlled by a complex system among the neutral and the ionized atmospheres, lower and upper atmospheres, and low-latitude and high-latitude ionospheres. As a result, the variation of EIA is difficult to be predicted. Meso-scale ionospheric structures, such as medium-scale traveling ionospheric disturbances (MSTID) and plasma bubbles, drift in about 100m/s of velocity and cause variations of short temporal scale. They were often observed to be accompanied by smaller scale structures that generate phase and amplitude scintillations of the GPS radio waves. The activity of MSTID has maxima in summer and winter. During these maximum periods, they were detected by GEONET almost everyday. Plasma bubbles were detected in the lowest latitude area of Japan, and found to reach the central part of Japan in a few days in a year. Most of them were in the geomagnetically disturbed periods. The geomagnetic disturbances also generate large-scale traveling ionospheric disturbances and reduction of TEC.

    Scopus

  405. Efficacy of STI571 for a patient with metastatic gastrointestinal stromal tumor 査読有り

    Sasaki, Y, Niwa, Y, Ando, N, Otsuka, Y, Ohmiya, N, Hirooka, Y, Itoh, A, Furuta, S, Goto, H

    HEPATO-GASTROENTEROLOGY   52 巻 ( 66 ) 頁: 1764 - 1767   2005年11月

  406. Observations of equatorial plasma bubbles using broadcast VHF radio waves 査読有り

    Nakata, H; Nagashima, I; Sakata, K; Otsuka, Y; Akaike, Y; Takano, T; Shimakura, S; Shiokawa, K; Ogawa, T

    GEOPHYSICAL RESEARCH LETTERS   32 巻 ( 17 )   2005年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005GL023243

    Web of Science

  407. Geomagnetic conjugate observation of nighttime medium-scale and large-scale traveling ionospheric disturbances: FRONT3 campaign

    Shiokawa, K; Otsuka, Y; Tsugawa, T; Ogawa, T; Saito, A; Ohshima, K; Kubota, M; Maruyama, T; Nakamura, T; Yamamoto, M; Wilkinson, P

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A5 ) 頁: doi:10.1029/2004JA010845   2005年5月

  408. Total electron content behavior over Japan during geomagnetic storms 査読有り

    Kutiev, I; Watanabe, S; Otsuka, Y; Saito, A

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A1 )   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004JA010586

    Web of Science

  409. Relationship between propagation direction of gravity waves in OH and OI airglow images and VHF radar echo occurrence during the SEEK-2 campaign 査読有り

    Onoma, F; Otsuka, Y; Shiokawa, K; Ogawa, T; Yamamoto, M; Fukao, S; Saito, S

    ANNALES GEOPHYSICAE   23 巻 ( 7 ) 頁: 2385 - 2390   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-23-2385-2005

    Web of Science

  410. Simultaneous ground- and satellite-based airglow observations of geomagnetic conjugate plasma bubbles in the equatorial anomaly 査読有り

    Ogawa, T; Sagawa, E; Otsuka, Y; Shiokawa, K; Immel, TI; Mende, SB; Wilkinson, P

    EARTH PLANETS AND SPACE   57 巻 ( 5 ) 頁: 385 - 392   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03351822

    Web of Science

  411. The first coordinated observations of mid-latitude E-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow 査読有り

    Ogawa T, Otsuka Y, Onoma F, Shiokawa K, Yamamoto M

    ANNALES GEOPHYSICAE   23 巻 ( 7 ) 頁: 2391 - 2399   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-23-2391-2005

    Web of Science

  412. Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes 査読有り

    Unnikrishnan, K; Saito, A; Otsuka, Y; Yamamoto, M; Fukao, S

    ANNALES GEOPHYSICAE   23 巻 ( 11 ) 頁: 3439 - 3450   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-23-3439-2005

    Web of Science

  413. Spatial relationship of equatorial plasma bubbles and field-aligned irregularities observed with an all-sky airglow imager and the Equatorial Atmosphere Radar 査読有り

    Otsuka, Y; Shiokawa, K; Ogawa, T; Yokoyama, T; Yamamoto, M; Fukao, S

    GEOPHYSICAL RESEARCH LETTERS   31 巻 ( 20 )   2004年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004GL020869

    Web of Science

  414. Statistical characteristics of gravity waves observed by an all-sky imager at Darwin, Australia 査読有り

    Suzuki, S; Shiokawa, K; Otsuka, Y; Ogawa, T; Wilkinson, P

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   109 巻 ( D20 ) 頁: D20 - S07   2004年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2003JD004336

    Web of Science

    Scopus

  415. Geomagnetic conjugate observations of medium-scale traveling ionospheric disturbances at midlatitude using all-sky airglow imagers 査読有り

    Otsuka, Y; Shiokawa, K; Ogawa, T; Wilkinson, P

    GEOPHYSICAL RESEARCH LETTERS   31 巻 ( 15 )   2004年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004GL020262

    Web of Science

  416. Comparison of OH rotational temperatures measured by the spectral airglow temperature imager (SATI) and by a tilting-filter photometer 査読有り

    Shiokawa, K; Otsuka, Y; Ogawa, T; Takahashi, H; Nakamura, T; Shimomai, T

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   66 巻 ( 11 ) 頁: 891 - 897   2004年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2004.03.003

    Web of Science

  417. A statistical study of large-scale traveling ionospheric disturbances using the GPS network in Japan 査読有り

    Tsugawa, T; Saito, A; Otsuka, Y

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   109 巻 ( A6 ) 頁: A06302   2004年6月

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    記述言語:日本語  

    DOI: 10.1029/2003JA010302

    Web of Science

  418. Simultaneous mesosphere/lower thermosphere and thermospheric F region observations during geomagnetic storms 査読有り

    Balan N, Kawamura S, Nakamura T, Yamamoto M, Fukao S, Igarashi K, Maruyama T, Shiokawa K, Otsuka Y, Ogawa T, Alleyne H, Watanabe S, Murayama Y

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   109 巻 ( A4 )   2004年4月

  419. Spatial relationship of equatorial plasma bubbles and field-aligned irregularities observed with an all-sky airglow imager and the Equatorial Atmosphere Radar 査読有り

    Otsuka, Y., K. Shiokawa, T. Ogawa, T. Yokoyama, M. Yamamoto, and S. Fukao

    Geophys. Res. Lett.   31 巻 ( L20802 ) 頁: 10.1029/2004GL020869   2004年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report, for the first time, simultaneous two-dimensional observations of 630-nm airglow depletions and radar backscatter from field-aligned irregularities (FAI) associated with equatorial plasma bubbles. Spatial distributions of backscatter were obtained by performing
    east-west scans with the 47-MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia. A 630-nm airglow depletion, caused by a plasma bubble, was simultaneously
    observed with an all-sky airglow imager.
    Both the airglow depletion and backscatter region appeared as band-like structure elongated in the meridional direction with a zonal width of about 100 km. To compare the spatial structures of backscatter with that of airglow depletion,
    the backscatter was projected onto a horizontal plane at 250-km altitude. Backscatter was found to occur within the entire airglow-depleted region.

  420. Generation of large-scale equatorial F-region plasma depletions during low range spread-F season 査読有り

    Sahai, Y; Fagundes, PR; Abalde, JR; Pimenta, AA; Bittencourt, JA; Otsuka, Y; Rios, VH

    ANNALES GEOPHYSICAE   22 巻 ( 1 ) 頁: 15 - 23   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-22-15-2004

    Web of Science

  421. Time evolution of high-altitude plasma bubbles imaged at geomagnetic conjugate points 査読有り

    Shiokawa, K; Otsuka, Y; Ogawa, T; Wilkinson, P

    ANNALES GEOPHYSICAE   22 巻 ( 9 ) 頁: 3137 - 3143   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-22-3137-2004

    Web of Science

  422. Ray-tracing Calculation of VHF Radio Waves Scattered by Field-aligned Irregularities Associated with Equatorial Plasma Bubbles 査読有り

    Hiroyuki Nakata, Yoshiaki Akaike, Yuichi Otsuka, Toshiaki Takano, Satoshi Ujigawa, Ikuo Nagashima

    IEEJ Transactions on Fundamentals and Materials   124 巻 ( 12 ) 頁: 1253 - 1254   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In order to explain the propagation of VHF radio waves for TV broadcasting transmitted from Southeast Asia associated with equatorial plasma bubbles, we have examined ray paths of the radio waves scattered by field-aligned irregularities in equatorial plasma bubbles. In determining the ray paths of the radio waves, a ray tracing calculation combined with a model of the scattering by field-aligned irregularities is used. It is found that VHF radio waves transmitted from Philippines can propagate to Japan due to scattering by field-aligned irregularities located above the East China Sea. © 2004, The Institute of Electrical Engineers of Japan. All rights reserved.

    DOI: 10.1541/ieejfms.124.1253

    Scopus

  423. Thermospheric wind during a storm-time large-scale traveling ionospheric disturbance 査読有り

    Shiokawa, K; Otsuka, Y; Ogawa, T; Kawamura, S; Yamamoto, M; Fukao, S; Nakamura, T; Tsuda, T; Balan, N; Igarashi, K; Lu, G; Saito, A; Yumoto, K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A12 )   2003年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2003JA010001

    Web of Science

  424. Optical and radio measurements of a 630-nm airglow enhancement over Japan on 9 September 1999 査読有り

    Otsuka, Y; Kadota, T; Shiokawa, K; Ogawa, T; Kawamura, S; Fukao, S; Zhang, SR

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A6 )   2003年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002JA009594

    Web of Science

  425. Ground and satellite observations of nighttime medium-scale traveling ionospheric disturbance at midlatitude 査読有り

    Shiokawa, K; Otsuka, Y; Ihara, C; Ogawa, T; Rich, FJ

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A4 )   2003年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002JA009639

    Web of Science

  426. Damping of large-scale traveling ionospheric disturbances detected with GPS networks during the geomagnetic storm 査読有り

    Tsugawa, T; Saito, A; Otsuka, Y; Yamamoto, M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A3 )   2003年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002JA009433

    Web of Science

  427. Statistical study of nighttime medium-scale traveling ionospheric disturbances using midlatitude airglow images 査読有り

    Shiokawa, K; Ihara, C; Otsuka, Y; Ogawa, T

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A1 )   2003年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002JA009491

    Web of Science

  428. Optical and radio measurements of a 630-nm enhancement over Japan on September 9, 1999 査読有り

    Otsuka, Y., T. Kadota, K. Shiokawa, T. Ogawa, S. Kawamura,, S. Fukao, and S. -R. Zhang

    J. Geophys. Res.   108(A6) 巻 ( 1252 ) 頁: doi:10.1029/2002JA009594   2003年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Using a comprehensive data set from optical and radio instruments, we investigate a midnight brightness wave that appeared in 630-nm airglow images over Japan on the night of September 9, 1999. This may be the first such observation of the brightness wave with an all-sky imager in the East-Asian longitudinal sector. The imager at Shigaraki (35.6N, 136.1E) tracked a north-northeastward propagation of the wave with an apparent velocity of 500 m/s after midnight. Ionosonde observations at five stations in Japan showed that rapid descent of the F2 layer propagated northward beyond 35N with decreasing amplitude. Incoherent scatter observations with the MU radar at Shigaraki also revealed that the F2 peak altitude decreased from 360 km to 280 km during the event. During the F2 layer descent, the altitude profile of the electron density became sharp, enhancing the F2 peak electron density. After the F2 layer altitude reached 280 km, electron density in the F2 layer rapidly decreased because of increased neutral density at low altitude. A Fabry-Perot interferometer (FPI) at Shigaraki observed northward neutral winds of 10--70 m/s during the event. A model calculation demonstrates that the meridional winds estimated from the MU radar electron density profiles are fairly well consistent with those observed with the FPI. From these results, we conclude that the observed northward wind enhancements, probably caused by the the midnight temperature maximum, pushed down the plasma in the F2 layer to lower altitudes along the geomagnetic field to cause the
    630-nm airglow intensity enhancement.

  429. A two-channel Fabry-Perot interferometer with thermoelectric-cooled CCD detectors for neutral wind measurement in the upper atmosphere 査読有り

    Shiokawa, K; Kadota, T; Otsuka, Y; Ogawa, T; Nakamura, T; Fukao, S

    EARTH PLANETS AND SPACE   55 巻 ( 5 ) 頁: 271 - 275   2003年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03351759

    Web of Science

  430. Simultaneous middle and upper atmosphere radar and ionospheric sounder observations of midlatitude E region irregularities and sporadic E layer 査読有り

    Ogawa T, Takahashi O, Otsuka Y, Nozaki K, Yamamoto M, Kita K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   107 巻 ( A10 )   2002年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2001JA900176

    Web of Science

  431. Annual and semiannual variations of the midlatitude ionosphere under low solar activity 査読有り

    Kawamura, S; Balan, N; Otsuka, Y; Fukao, S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   107 巻 ( A8 )   2002年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2001JA999267

    Web of Science

  432. Geomagnetic conjugate observations of equatorial airglow depletions 査読有り

    Otsuka, Y; Shiokawa, K; Ogawa, T; Wilkinson, P

    GEOPHYSICAL RESEARCH LETTERS   29 巻 ( 15 )   2002年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002GL015347

    Web of Science

  433. A large-scale traveling ionospheric disturbance during the magnetic storm of 15 September 1999 査読有り

    Shiokawa, K; Otsuka, Y; Ogawa, T; Balan, N; Igarashi, K; Ridley, AJ; Knipp, DJ; Saito, A; Yumoto, K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   107 巻 ( A6 )   2002年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2001JA000245

    Web of Science

  434. Geomagnetic conjugate observations of equatorial airglow depletions 査読有り

    Otsuka, Y., K. Shiokawa, T. Ogawa, and P. Wilkinson

    Geophys. Res. Lett.   29 巻   頁: 10.1029/2002GL015347   2002年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  435. A new technique for mapping of total electron content using GPS network in Japan 査読有り

    Otsuka, Y; Ogawa, T; Saito, A; Tsugawa, T; Fukao, S; Miyazaki, S

    EARTH PLANETS AND SPACE   54 巻 ( 1 ) 頁: 63 - 70   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352422

    Web of Science

  436. Imaging observations of the equatorward limit of midlatitude traveling ionospheric disturbances 査読有り

    Shiokawa, K; Otsuka, Y; Ejiri, MK; Sahai, Y; Kadota, T; Ihara, C; Ogawa, T; Igarashi, K; Miyazaki, S; Saito, A

    EARTH PLANETS AND SPACE   54 巻 ( 1 ) 頁: 57 - 62   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352421

    Web of Science

  437. Observations and modeling of 630 nm airglow and total electron content associated with traveling ionospheric disturbances over Shigaraki, Japan 査読有り

    Ogawa, T; Balan, N; Otsuka, Y; Shiokawa, K; Ihara, C; Shimomai, T; Saito, A

    EARTH PLANETS AND SPACE   54 巻 ( 1 ) 頁: 45 - 56   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352420

    Web of Science

  438. Observations of traveling ionospheric disturbances and 3-m scale irregularities in the nighttime F-region ionosphere with the MU radar and a GPS network 査読有り

    Saito A, Nishimura M, Yamamoto M, Fukao S, Tsugawa T, Otsuka Y, Miyazaki S, Kelley MC

    EARTH PLANETS AND SPACE   54 巻 ( 1 ) 頁: 31 - 44   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352419

    Web of Science

  439. Plasmaspheric electron content in the GPS ray paths over Japan under magnetically quiet conditions at high solar activity 査読有り

    Balan, N; Otsuka, Y; Tsugawa, T; Miyazaki, S; Ogawa, T; Shiokawa, K

    EARTH PLANETS AND SPACE   54 巻 ( 1 ) 頁: 71 - 79   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352423

    Web of Science

  440. Regional ionosphere map over Japanese Islands 査読有り

    Ping, J; Kono, Y; Matsumoto, K; Otsuka, Y; Saito, A; Shum, C; Heki, K; Kawano, N

    EARTH PLANETS AND SPACE   54 巻 ( 12 ) 頁: E13 - E16   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/BF03352450

    Web of Science

  441. Annual and semiannual variations of the midlatitude ionosphere under low solar activity 査読有り

    S. Kawamura, N. Balan, Y. Otsuka, S. Fukao

    Journal of Geophysical Research: Space Physics   107 巻 ( 8 )   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    The annual and semiannual variations of the midlatitude ionosphere under low solar activity are studied using middle and upper (MU) radar (135°E, 35°N) incoherent scatter observations and Sheffield University plasmasphere-ionosphere model (SUPIM). The variations of the daytime electron density (Ne) and electron and ion temperatures (Te and Ti) at 200-600 km altitudes measured by the radar under low solar activity (F10.7 ≤ 120) are satisfactorily reproduced for the first time by incorporating the radar measured values of the magnetic meridional neutral wind velocity (U 0) and northward perpendicular plasma drift velocity (V ⊥) into SUPIM that uses mass spectrometer incoherent scatter 1986 (MSIS-86) for neutral densities and neutral temperatures. The study shows that the annual and semiannual variations of the midlatitude ionosphere during daytime at altitudes near and above the ionospheric peak under low solar activity depend more on the direct effect of the neutral wind arising through the changes in ionospheric height than on the indirect effect arising through the changes in thermospheric composition (or atomic to molecular concentration ratio)
    the indirect effect, however, predominates on the variations at altitudes below the ionospheric peak. The electron temperature (Te) undergoes similar but almost opposite seasonal and semiannual variations as the electron density. The ion temperature (Ti) is closer to neutral temperature than to electron temperature at altitudes up to ∼400 km and shows comparatively weak annual and semiannual variations. Copyright 2002 by the American Geophysical Union.

    DOI: 10.1029/2001JA000267

    Scopus

  442. Imaging observations of midlatitude ionospheric disturbances during the geomagnetic storm of February 12, 2000 査読有り

    Y Sahai, K Shiokawa, Y Otsuka, C Ihara, T Ogawa, K Igarashi, S Miyazaki, A Saito

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A11 ) 頁: 24481 - 24492   2001年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Regular all-sky imaging observations of the F region OI 630 nm nightglow emission are carried out at Rikubetsu (43.5 degreesN) and Shigaraki (34.8 degreesN), Japan since 1998. In this paper, we present observations of the OI 630 nm emission images from these two sites with a cluster of other observations during the geomagnetic storm of February 12, 2000. The airglow observations were obtained between 1500 UT and 2000 UT (0000-0500 LT) on this night. Images from both Rikubetsu and Shigaraki show the presence of mesoscale-enhanced airglow bands moving slowly (similar to 20-30 m s(-1)) to the southwest direction. The mesoscale band structures were also detected by an extensive network of GPS signal observations over Japan. The airglow observations at Shigaraki also show intense OI 630 nm emission in the south with several small-scale intensity depletion structures. We suggest that these small-scale intensity depletion structures (scale size 30-50 km) are caused by possible nonlinear interaction between the mesoscale TIDs and enhanced regions of the equatorial ionospheric anomaly. The ionosonde observations from Wakkanai (45.4 degreesN) and Kokubunji (35.7 degreesN) show spread F signatures between 1130 and 2100 UT and 1215 and 1715 UT, respectively, whereas no spread F was observed at Yamagawa (31.2 degreesN) and Okinawa (26.3 degreesN). The phase fluctuations of GPS signal were observed at latitudes higher than 30 degreesN for 1400-1900 UT. These observations suggest enhanced storm time ionospheric disturbances were confined in the midlatitudes.

    Web of Science

  443. Three-channel imaging Fabry-Perot interferometer for measurement of mid-latitude airglow 査読有り

    Shiokawa, K; Kadota, T; Ejiri, MK; Otsuka, Y; Katoh, Y; Satoh, M; Ogawa, T

    APPLIED OPTICS   40 巻 ( 24 ) 頁: 4286 - 4296   2001年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1364/AO.40.004286

    Web of Science

    PubMed

  444. Traveling ionospheric disturbances detected in the FRONT campaign 査読有り

    Saito, A; Nishimura, M; Yamamoto, M; Fukao, S; Kubota, M; Shiokawa, K; Otsuka, Y; Tsugawa, T; Ogawa, T; Ishii, M; Sakanoi, T; Miyazaki, S

    GEOPHYSICAL RESEARCH LETTERS   28 巻 ( 4 ) 頁: 689 - 692   2001年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2000GL011884

    Web of Science

  445. Multi-point observation of short-period mesospheric gravity waves over Japan during the FRONT campaign 査読有り

    Shiokawa, K; Ejiri, MK; Otsuka, Y; Ogawa, T; Kubota, M; Igarashi, K; Saito, A; Nakamura, T

    GEOPHYSICAL RESEARCH LETTERS   27 巻 ( 24 ) 頁: 4057 - 4060   2000年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2000GL011917

    Web of Science

  446. Traveling ionospheric disturbances observed in the OI 630-nm nightglow images over Japan by using a multipoint imager network during the FRONT campaign 査読有り

    Kubota, M; Shiokawa, K; Ejiri, MK; Otsuka, Y; Ogawa, T; Sakanoi, T; Fukunishi, H; Yamamoto, M; Fukao, S; Saito, A

    GEOPHYSICAL RESEARCH LETTERS   27 巻 ( 24 ) 頁: 4037 - 4040   2000年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2000GL011858

    Web of Science

  447. Comprehensive imaging observations of midlatitude ionospheric disturbances during storm time substorms 査読有り

    Shiokawa, K; Otsuka, Y; Ogawa, T; Igarashi, K; Miyazaki, S; Rich, FJ; Saito, A; Yumoto, Y

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A12 ) 頁: 27067 - 27080   2000年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2000JA900099

    Web of Science

  448. A study of the forenoon ionospheric F-2 layer behavior over the middle and upper atmospheric radar 査読有り

    Zhang, SR, WL Oliver, S Fukao, Y Otsuka

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A7 ) 頁: 15823 - 15833   2000年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The middle and upper atmosphere (MU) radar incoherent Scatter observations of electron density N-e profiles for 1986-1995 at Shigaraki (34.85 degrees N, 136.10 degrees E) show a forenoon density depression (bite-out) in summer bo th on individual days and in statistical averages. The depression takes place generally between 0700 and 1200 LT, above the F-2 peak for low solar activity and around the F-2 peak for high solar activity. The maximum electron density NmF2 shows, in both percentage and time duration, a greater depression for low solar activity than for high solar activity. With increasing altitude, the forenoon N-e depression develops earlier for low solar activity. In combination with the MU radar observations of ion drifts and plasma; temperatures, our modeling indicates the following: (1) Transport processes such as the enhancement of electron temperature T-e, the poleward neutral wind, and the reduced upper boundary ionization density help to reduce N-e and result in a negative partial derivative N-e/partial derivative t in the morning hours in summer. Among those processes the morning enhancement of T-e is found to be most important for the presence of the forenoon bite-out, since it greatly increases the O+ diffusion such that ionization outflow is significantly intensified. (2) The forenoon bite-out occurs only in summer, not in other seasons, because the smaller atmospheric composition ratio [O]/[N-2] in summer leads to a smaller daytime background N-e and thus to an enhanced T-e, and the after-sunrise photochemical contributions (mainly the O+ production) are so small that partial derivative Ne/partial derivative t also tends to be smaller. These two conditions give prominence to the transport contributions. (3) The solar activity dependences of the forenoon bite-out can be explained basically in terms of the low-electron-density background. (4) The height of formation of the forenoon bite-out is also related to the sunrise effect on photoionization.

    DOI: 10.1029/2000JA000007

    Web of Science

  449. A climatology of middle and upper atmosphere radar observations of thermospheric winds 査読有り

    S Kawamura, Y Otsuka, Zhang, SR, S Fukao, WL Oliver

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A6 ) 頁: 12777 - 12788   2000年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Shigaraki middle and upper atmosphere (MU) radar observations of horizontal thermospheric winds in the magnetic meridian plane over the period September 1986 to September 1996 are reported as climatological averages in the form of time-of-day variations for several combinations of seasonal and solar activity conditions and are compared with winds predicted by the horizontal wind model (HWM) anti with winds measured at Saint Santin and Millstone Hill. The dominant feature of the MU wind behavior is its mean diurnal variation of northward flow by day and southward flow by night, with the nighttime wind smoothly approaching and receding from a midnight maximum, while the daytime wind tends to show two peaks, a strong. one in the early daylight hours and a weak one in the afternoon-evening. HWM shows the same unimodal nighttime and bimodal daytime behavior, but the HWM pattern is shifted about 2 hours later in time. The amplitude of the diurnal harmonic decreases from 78 m/s at solar minimum to 45 m/s at solar maximum, while: HWM shows a corresponding increase from 53 to 62 m/s. The diurnal amplitude is remarkably stable with season but is superposed on a steady willd of 41 m/s southward in summer, 15 m/s northward in winter, and midway between these limits at the equinoxes. HWM shows a symmetric pattern of 30 m/s southward in summer and 30 m/s northward ill winter. Ion drag appears to be the main regulator of wind speed, and the seasonal wind patterns have a profound effect on the seasonal behavior of the ionosphere.

    Web of Science

  450. The IRI's B parameters measured by the MU radar 査読有り

    Zhang, SR, S Fukao, XY Huang, Y Otsuka

    LOWER IONOSPHERE: MEASUREMENTS AND MODELS   25 巻 ( 1 ) 頁: 101 - 104   2000年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON PRESS LTD  

    The IS measurements of power profile by the MU radar at Shigaraki (34.9 degrees N, 136.1 degrees E) are analyzed to give IRI's B-parameters, B0 B1 for 1986-1991. Empirical formulas are obtained to represent their variations as functions of local time and season at high solar activity. They are compared also with ionosonde ones for Wuchang (30.5 degrees N, 114.4 degrees E). (C) 1999 COSPAR. Published by Elsevier Science Ltd.

    Web of Science

  451. Annual variations of the ionosphere: A review based on MU radar observations 査読有り

    N Balan, Y Otsuka, S Fukao, MA Abdu, GJ Bailey

    LOWER IONOSPHERE: MEASUREMENTS AND MODELS   25 巻 ( 1 ) 頁: 153 - 162   2000年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON PRESS LTD  

    A review of the annual variations of the ionosphere, which focuses on the physical mechanisms causing the well-known seasonal anomaly and equinoctial asymmetry, is presented. In this review, the electron density (Nc), electron and ion temperatures (Te and Ti). and field-parallel and field-perpendicular plasma velocities (V-parallel to and V-perpendicular to), measured by the MU radar in the 180-600 km altitude range during 1986-1994, are analysed to study the altitude dependence of the seasonal anomaly and equinoctial asymmetry. The meridional component of the thermospheric neutral wind velocity (U-theta) derived from V-parallel to and neutral densities obtained from MSIS-86 are used to investigate the relative importance of the chemical and dynamical processes causing the anomaly and asymmetry. The review concludes that, although the anomaly and asymmetry involve chemical and dynamical processes, the dynamical processes (mainly through the neutral wind) predominate in the asymmetry while the chemical processes predominate in the anomaly. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

    Web of Science

  452. The height of the maximum ionospheric electron density over the MU radar 査読有り

    Zhang, SR, S Fukao, WL Oliver, Y Otsuka

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   61 巻 ( 18 ) 頁: 1367 - 1383   1999年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Ionospheric F-2-layer peak height h(m)F(2) variations, as measured over 1986-1995 by the MU radar (34.85 degrees N, 136.1 degrees E) and as calculated with a theoretical model, are discussed. The diurnal variations of the measured peak height for different seasons and levels of solar activity are compared with those estimated from ionosonde M3000F(2) and IRI predictions. Also given are the measured ion drift velocities and meridional neutral winds needed to understand the dynamic behavior of the F-2-layer. It is found that: (1) h(m)F(2) is generally higher during periods of the solar maximum than during periods of the solar minimum, and higher in summer than in winter; (2) for the solar maximum, h(m)F(2) drops markedly in the morning and in the afternoon, while, for the solar minimum, the h(m)F(2) minimum occurs in the morning during summer and usually in the afternoon during winter. In general, the measured h(m)F(2) is well reproduced by our model when we use the observed drift velocities and plasma temperatures as inputs. Our modeling study shows that the neutral wind contributes strongly to the diurnal variation of h(m)F(2) in winter by lowering the ionization layer by day, particularly for the solar maximum; it also helps to enlarge the daynight difference of h(m)F(2) in summer. The northward electromagnetic drifts that usually cancel the neutral wind effect have only a minor effect for the location of the MU radar. Other features of the observed h(m)F(2) variations, e.g., the solar maximum-minimum difference, the summer-winter difference, and the morning and afternoon drops, are explained by the basic processes of O+ production, loss and diffusion, as influenced by the atomic oxygen concentration and neutral and plasma temperatures. (C) 2000 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S1364-6826(99)00088-7

    Web of Science

  453. The height of the maximum ionospheric electron density over the MU radar 査読有り

    Journal of Atmospheric and Solar-Terrestrial Physics   61 巻   頁: 1367-83   1999年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  454. MU radar observations of H+ ions in the topside ionosphere 査読有り

    Kawamura S, Otsuka Y, Oliver WL, Balan N, Fukao S

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A9 ) 頁: 20697 - 20704   1998年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/98JA00898

    Web of Science

  455. Plasma temperature variations in the ionosphere over the middle and upper atmosphere radar 査読有り

    Otsuka, Y; Kawamura, S; Balan, N; Fukao, S; Bailey, GJ

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A9 ) 頁: 20705 - 20713   1998年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/98JA01748

    Web of Science

  456. MST radar measurement of ionospheric F region winds: The "layer wind" technique 査読有り

    WL Oliver, Y Otsuka, S Fukao

    RADIO SCIENCE   33 巻 ( 4 ) 頁: 941 - 948   1998年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We develop an improved application of the mesosphere-stratospheretroposphere (MST) radar technique for the measurement of winds at ionospheric F region altitudes. While the experiment is basically one of incoherent scatter (IS), which yields very weak signals at the usual operating frequencies of MST radars, we develop an analysis technique that allows the signals to be integrated over the entire F region of the ionosphere to gain sufficient statistical accuracy to compute the "layer wind" accurately. This method is contrasted with the normal IS method of determining winds at discrete heights. The method is applied to data collected with the middle and upper atmosphere radar in Japan, though it is applicable to any MST radar having a comparable or even somewhat smaller power-aperture product and may also be adapted for improved results from mainline IS radars. Using this method, we are able to discuss confidently the geophysical behavior of the wind on individual days, whereas previously we were reluctant to discuss anything but climatological features from data averages.

    DOI: 10.1029/98RS00658

    Web of Science

  457. Equinoctial asymmetries in the ionosphere and thermosphere observed by the MU radar 査読有り

    N Balan, Y Otsuka, GJ Bailey, S Fukao

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A5 ) 頁: 9481 - 9495   1998年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Annual variations of the ionosphere and thermosphere studied with the middle and upper atmosphere (MU) radar during the solar maximum period 1988-1992 show that the well-known seasonal anomaly in the electron density Ne exists only during daytime and at altitudes near the ionospheric peak and below. The observations also reveal the existence of equinoctial asymmetries in the ionosphere and thermosphere, with the asymmetry in the ionosphere changing its character with altitude during daytime. In the bottomside ionosphere the electron density Ne is slightly greater in September equinox than in March equinox. At higher altitudes the asymmetry reverses and becomes strong; the values of Ne in March equinox exceed those in September equinox by up to 100%. The electron temperature Te exhibits equinoctial asymmetries almost opposite those in Ne. The ion temperature Ti shows a weak asymmetry, in phase with the asymmetry in Ne. The field-aligned and field-perpendicular plasma velocities V-parallel to and V-perpendicular to are also different in the two equinoxes. In the thermosphere the neutral wind and composition show consistent equinoctial asymmetries. The meridional component of the daytime poleward wind velocity (U-theta) derived from the field-parallel plasma velocity is weaker in March equinox than in September equinox by up to 20 m s(-1), and the values of the daytime [O]/[N-2] ratio obtained from MSIS-86 are larger in September equinox than in March equinox by about 20%. Model calculations carried out by incorporating the measured V-perpendicular to and U-theta into the Sheffield University plasmasphere-ionosphere model that uses MSIS-86 for neutral atmosphere show that the equinoctial asymmetries in the ionosphere arise mainly from the corresponding asymmetries in the thermosphere, with major contributions from neutral winds and minor contributions from composition.

    DOI: 10.1029/97JA03137

    Web of Science

  458. Plasma temperature variations in the ionosphereover the middle and upper atmosphere radar 査読有り

    Journal of Geophysical Research   103 巻   頁: 20,705-20,713   1998年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

  459. MU radar observations of H+ ions in the topside ionosphere 査読有り

    Journal of Geophysical Research   103 巻   頁: 20,697-20,704   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  460. MST radar measurement of ionospheric F region winds:The "layer-wind" technique 査読有り

    Radio Science   33 巻   頁: 941-948   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  461. Equinoctial asymmetries in the ionosphere and thermosphere observed by the MU radar 査読有り

    Journal of Geophysical Research   103 巻   頁: 9,481-9,495   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  462. New aspects in the annual variation of the ionosphere observed by the MU radar 査読有り

    N Balan, Y Otsuka, S Fukao

    GEOPHYSICAL RESEARCH LETTERS   24 巻 ( 18 ) 頁: 2287 - 2290   1997年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Annual variations of the daytime ionosphere studied with the MU radar during a full solar cycle show equinoctial asymmetry in density, temperature, and plasma velocity. The electron density (Ne) in the bottomside ionosphere is slightly greater in September equinox compared to March equinox, which arises from the asymmetry in thermospheric composition. At higher altitudes, the asymmetry in Ne reverses and becomes strong; the values of Ne in March equinox exceed those in September equinox by up to 150%. The electron temperature (Te) shows an asymmetry, which is opposite to the asymmetry in Ne; the values of Te in the topside in March equinox are less than those in September equinox by up to 300K. The asymmetry in ion temperature (Ti) is weak (about 100K) and in phase with the asymmetry in Ne. The northward perpendicular plasma velocity (V-perpendicular to) is slightly greater in March equinox compared to September equinox. The meridional component of the thermospheric neutral wind velocity (U-theta), derived from the field-parallel plasma velocity V-parallel to, is up to 50% lower in March equinox compared to September equinox. The asymmetry in neutral winds accounts for the asymmetry in ionospheric density and temperature in the topside, with minor contribution from the asymmetry in plasma drifts.

    DOI: 10.1029/97GL02184

    Web of Science

  463. A climatology of F region gravity wave propagation over the middle and upper atmosphere radar 査読有り

    WL Oliver, Y Otsuka, M Sato, T Takami, S Fukao

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   102 巻 ( A7 ) 頁: 14499 - 14512   1997年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    By observing the ionospheric F region simultaneously in multiple beams with the middle and upper atmosphere radar, we have been able to track the passage of gravity waves and measure their propagation characteristics. Here we develop a climatology of wave propagation based on the observation of 58 daytime experiments conducted during 1986-1994. The thermosphere seems to be continuously swept by waves detectable by an incoherent scatter radar. These waves generally come for hours on end from a,consistent or slowly varying direction, which can be any direction on a given day. Statistically, the waves show a moderate preference for southward travel, with this preference being reduced or shifted to southeastward travel during disturbed times. On average, the horizontal phase trace speed remains near 240 m/s for all periods inspected (40-130 min). This speed matches the behavior expected for lossless waves with 150-200 km vertical wavelength. We find small variability in this relation for different times of day, seasons, solar and magnetic conditions, and directions of wave travel, though waves on disturbed days seem to travel moderately faster on solar minimum mornings.

    DOI: 10.1029/97JA00491

    Web of Science

  464. A climatology of F region gravity wave propagation over the middle and upper atmosphere radar 査読有り

    Journal of Geophysical Research   102 巻   頁: 14,499-14,512   1997年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  465. New aspects in the annual variation of the ionosphere observed by the MU radar 査読有り

    Geophysical Research Letters   24 巻   頁: 2,287-2,290   1997年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  466. Middle and upper atmosphere radar observations of the dispersion relation for ionospheric gravity waves 査読有り

    Journal of Geophysical Research   100 巻   頁: 23,763-23,768   1995年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

▼全件表示

MISC 161

  1. S-520-27号機観測ロケットによる夜間中規模伝搬性電離圏擾乱発生時の電場観測結果

    松山実由規, 石坂圭吾, 山本衛, 斎藤享, 高橋透, 大塚雄一, 熊本篤志, 田中真, 阿部琢美  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)154th 巻   2023年

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  2. ハワイで得られた大気光画像に見られる大気重力波・MSITDsの波源及び生成機構の解析

    内藤豪人, 塩川和夫, 大塚雄一, 坂野井健, 齊藤昭則, 中村卓司  

    日本地球惑星科学連合大会予稿集(Web)2020 巻   2020年

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  3. 赤道プラズマバブルの急速な発達と中緯度帯への影響

    横山竜宏, 品川裕之, 陣英克, 大塚雄一  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)148th 巻   2020年

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  4. 赤道プラズマバブルの中緯度帯への影響

    横山竜宏, 品川裕之, 大塚雄一  

    日本地球惑星科学連合大会予稿集(Web)2020 巻   2020年

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  5. ハワイで得られた大気光画像に見られる大気重力波とMSTIDの相関及びこれらの波動と対流圏上昇流の相関

    内藤豪人, 塩川和夫, 大塚雄一, 藤波初木, 坂野井健, 齊藤昭則, 中村卓司  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)148th 巻   2020年

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  6. 無人システムを利用したオーロラ現象の南極広域ネットワーク観測:共役点イベント解析(2)

    門倉昭, 山岸久雄, 岡田雅樹, 小川泰信, 田中良昌, 片岡龍峰, 内田ヘルベルト陽仁, 大塚雄一  

    日本地球惑星科学連合大会予稿集(Web)2019 巻   頁: ROMBUNNO.PEM11‐23 (WEB ONLY)   2019年

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    記述言語:日本語  

    J-GLOBAL

  7. 電離圏/プラズマ圏系の動力学: あらせ/PWE観測とIPEモデルシミュレーションの比較

    OBANA Yuki, MARUYAMA Naomi, SHINBORI Atsuki, HASHIMOTO Kumiko, FEDRIZZI Mariangel, NOSE Masahito, OTSUKA Yuichi, NISHITANI Nozomu, HORI Tomoaki, KUMAMOTO Atsushi, TSUCHIYA Fuminori, MATSUDA Shoya, MATSUOKA Ayako, KASAHARA Yoshiya, YOSHIKAWA Akimasa, MIYOSHI Yoshizumi, SHINOHARA Iku  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)146th 巻   2019年

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  8. ハワイの大気光画像中に見られる中間圏・電離圏波動の水平位相速度・パワースペクトル密度分布の統計解析及びイベント解析

    内藤豪人, 塩川和夫, 大塚雄一, 坂野井健, 齊藤昭則, 中村卓司  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)146th 巻   2019年

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  9. あらせ(ERG)で観測されたヘクトメータ線スペクトルの励起源と波動特性

    橋本弘藏, 熊本篤志, 土屋史紀, 笠原禎也, 三好由純, 大塚雄一, 新堀淳樹, 横山竜宏, 長野勇, 松岡彩子  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)146th 巻   2019年

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  10. ハワイで得られた大気光画像中に見られる中間圏・電離圏波動の水平位相速度分布の統計解析

    内藤豪人, 塩川和夫, 大塚雄一, 坂野井健, 齊藤昭則, 中村卓司  

    日本地球惑星科学連合大会予稿集(Web)2019 巻   2019年

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  11. 2017年9月7~10日の磁気嵐の際のプラズマ圏の極端侵蝕作用

    OBANA Yuki, MARUYAMA Naomi, MARUYAMA Naomi, SHINBORI Atsuki, HASHIMOTO Kumiko K., FEDRIZZI Mariangel, FEDRIZZI Mariangel, NOSE Masahito, OTSUKA Yuichi, NISHITANI Nozomu, HORI Tomoaki, KUMAMOTO Atsushi, TSUCHIYA Fuminori, MATSUDA Shoya, MATSUOKA Ayako, KASAHARA Yoshiya, YOSHIKAWA Akimasa, MIYOSHI Yoshizumi, SHINOHARA Iku  

    日本地球惑星科学連合大会予稿集(Web)2019 巻   2019年

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  12. GAIAを用いた赤道プラズマバブルの発生・成長を支配するパラメータの解析

    品川裕之, 陣英克, 三好勉信, 藤原均, 横山竜宏, 大塚雄一  

    日本地球惑星科学連合大会予稿集(Web)2019 巻   頁: ROMBUNNO.PEM16‐P14 (WEB ONLY)   2019年

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    記述言語:日本語  

    J-GLOBAL

  13. 陸別・信楽・アサバスカ・マガダンの大気光画像を用いた中間圏大気重力波・中規 模伝搬性電離圏擾乱の水平波数分布の長期統計解析

    土屋智, 塩川和夫, 大塚雄一, 中村卓司, 山本衛, Connors Martin, Schofield Ian, Shevtsov Boris, Poddelsky Igor  

    地球電磁気・地球惑星圏学会第144回総会・講演会   2018年11月

  14. Equatorial Plasma Bubble (EPB) to atmosphere relationship found from day-to-day variation of GPS scintillation and GAIA assimilation data

    Mamoru Yamamoto, Yuichi Otsuka, Hidekatsu Jin, Yasunobu Miyoshi  

    ISEA-15   2018年10月

  15. レベルセット法を用いた陽子オーロラの空間特徴の検出

    井上智寛, 尾崎光紀, 八木谷聡, 塩川和夫, 三好由純, 新堀淳樹, 大塚雄一, 片岡龍峰, 海老原祐輔, 津川卓也, 西岡未知  

    電気関係学会北陸支部連合大会講演論文集(CD-ROM)2018 巻   頁: ROMBUNNO.F2‐37   2018年9月

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    記述言語:日本語  

    J-GLOBAL

  16. Results of joint ionospheric measurements with Kharkiv incoherent scatter and MU radars during near-equinox and solstice periods

    Sergii Panasenko, Dmytro V. Kotov, Oleksandr V. Bogomaz, Yuichi Otsuka, Mamoru Yamamoto, Hiroyuki Hashiguchi・Leonid, Ya. Emelyanov・Igor, F. Domnin  

    第12回MUレーダー・赤道大気レーダーシンポジウム   2018年9月

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    記述言語:英語  

  17. 日本・カナダの大気光画像を用いた中間圏重力波・TIDの水平位相速度分布の長期統計解析

    土屋 智, 塩川 和夫, 藤波 初木, 大塚 雄一, 中村 卓司, 山本 衛, イアン スコフィールド, マーチン コナーズ  

    日本地球惑星科学連合2018年大会   2018年5月

  18. Role of the pre-reversal enhancement and medium-scale gravity waves on multiple plasma bubbles occurrence

    Prayitno Abadi, Yuichi Otsuka, Kazuo Shiokawa, Mamoru Yamamoto, Huixin Liu, Tatsuhiro Yokoyama  

    日本地球惑星科学連合2018年大会   2018年5月

  19. 地球の内部磁気圏のプラズマ変動に起因するオーロラ・電磁場変動の観測

    塩川和夫, 三好由純, 大山伸一郎, 西谷望, 関華奈子, 大塚雄一, 尾崎光紀, 片岡龍峰, 長妻努, 田中良昌, 篠原育, 能勢正仁, 坂野井健, 土屋史紀, 尾花由紀, 鈴木臣, 新堀敦樹, 堀智昭, 高橋直子, 栗田怜, 坂口歌織  

    日本物理学会講演概要集(CD-ROM)73 巻 ( 1 ) 頁: ROMBUNNO.22aK608‐6   2018年3月

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    記述言語:日本語  

    J-GLOBAL

  20. 石垣島で取得された630.0nm大気光観測データを用いたプラズマバブルの形状解析

    高見晃平, 細川敬祐, 斎藤享, 小川泰信, 塩川和夫, 大塚雄一  

    地球電磁気・地球惑星圏学会総会及び講演会(Web)144th 巻   頁: ROMBUNNO.R005‐P10 (WEB ONLY)   2018年