2021/04/24 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 2

  1. 電離圏 大気光 全電子数 GPS GNSS

  2. 電離圏物理学

研究分野 2

  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

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 5

  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

  2. 名古屋大学太陽地球環境研究所・准教授

    2011年11月 - 2015年10月

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    国名:日本国

  3. 名古屋大学太陽地球環境研究所・助教

    2008年4月 - 2011年10月

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    国名:日本国

  4. 名古屋大学太陽地球環境研究所・助手

    1999年9月 - 2008年3月

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    国名:日本国

  5. 中核的研究機関研究員(京都大学超高層電波研究センター)

    1999年4月 - 1999年8月

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    国名:日本国

学歴 3

  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

    1994年4月 - 1996年3月

  3. 京都大学   理学部

    1990年4月 - 1994年3月

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    国名: 日本国

所属学協会 4

  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

受賞 5

  1. 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

  2. EPS Award

    2009年5月   Earth, Planets and Space  

  3. 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  

  4. 2011年 Radio Science 誌優秀論文審査賞

    2011年   米国地球物理連合  

  5. Excellent Reviewers 2020

    2021年1月   Earth, Planets and Space  

 

論文 359

  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. Equatorial Plasma Bubble Occurrence Under Propagation of MSTID and MLT Gravity Waves

    Takahashi H., Wrasse C. M., Figueiredo C. A. O. B., Barros D., Paulino I., Essien P., Abdu M. A., Otsuka Y., Shiokawa K.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 9 )   2020年9月

  7. Temporal and Spatial Variations of Total Electron Content Enhancements During a Geomagnetic Storm on 27 and 28 September 2017

    Shinbori Atsuki, Otsuka Yuichi, Sori Takuya, Tsugawa Takuya, Nishioka Michi

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 7 )   2020年7月

  8. Equatorial Plasma Bubble Zonal Drift Velocity Variations in Response to Season, Local Time, and Solar Activity across Southeast Asia

    Sarudin I., Hamid N. S. A., Abdullah M., Buhari S. M., Shiokawa K., Otsuka Y., Yatini C. Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 3 )   2020年3月

  9. Wavenumber Spectra of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances Based on More Than 10-Year Airglow Images in Japan, Russia, and Canada

    Tsuchiya Satoshi, Shiokawa Kazuo, Otsuka Yuichi, Nakamura Takuji, Yamamoto Mamoru, Connors Martin, Schofield Ian, Shevtsov Boris, Poddelsky Igor

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 3 )   2020年3月

  10. Multievent Analysis of Oscillatory Motion of Medium-Scale Traveling Ionospheric Disturbances Observed by a 630-nm Airglow Imager Over Tromso

    Yadav Sneha, Shiokawa K., Oyama S., Otsuka Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 3 )   2020年3月

  11. Characteristics of GNSS Total Electron Content Enhancements Over the Midlatitudes During a Geomagnetic Storm on 7 and 8 November 2004

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

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 12 ) 頁: 10376 - 10394   2019年12月

  12. IpsDst of Dst Storms Applied to Ionosphere-Thermosphere Storms and Low-Latitude Aurora

    Balan N., Zhang Qing -He, Shiokawa K., Skoug R., Xing Zanyang, Ram S. Tulasi, Otsuka Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 11 ) 頁: 9552 - 9565   2019年11月

  13. Statistical Study of Auroral/Resonant-Scattering 427.8-nm Emission Observed at Subauroral Latitudes Over 14 Years

    Shiokawa K., Otsuka Y., Connors M.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 11 ) 頁: 9293 - 9301   2019年11月

  14. Climatology of Equatorial Plasma Bubble Observed by MyRTKnet over the Years 2008-2013

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

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

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  15. GAST-D flight experiment results with disturbed and quiet ionospheric conditions

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

    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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  16. Direct observations of blob deformation during a substorm

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

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

  17. The observation of equatorial plasma bubble using all sky imager and GPS TEC measurement

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

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

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  18. Two-dimensional structure of equatorial plasma bubble observed using GPS networks in South East Asia region

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

    2014 INTERNATIONAL CONFERENCE ON ELECTRONICS, INFORMATION AND COMMUNICATIONS (ICEIC)     2014年

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  19. Typhoon-induced concentric airglow structures in the mesopause region

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

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

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

    Ozeki Yasuyuki, Otsuka Yoichi, Sato Shuya, Hashimoto Hiroyuki, Umemura Wataru, Sumimura Kazuhiko, Nishizawa Norihiko, Fukui Kiichi, Itoh Kazuyoshi

    MULTIPHOTON MICROSCOPY IN THE BIOMEDICAL SCIENCES XIII   8588 巻   2013年

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

    Saito S., Yoshihara T., Otsuka Y.

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

    Ozeki Yasuyuki, Umemura Wataru, Otsuka Yoichi, Satoh Shuya, Hashimoto Hiroyuki, Sumimura Kazuhiko, Nishizawa Norihiko, Fukui Kiichi, Itoh Kazuyoshi

    NATURE PHOTONICS   6 巻 ( 12 ) 頁: 844 - 850   2012年12月

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

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

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

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

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

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

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

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

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

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

    Kutiev Ivan, Otsuka Yuichi, Pancheva Dora, Heelis Rod

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

  27. Significance of C4d deposition in antibody-mediated rejection

    Takeda Asami, Otsuka Yasuhiro, Horike Keiji, Inaguma Daijo, Hiramitsu Takahisa, Yamamoto Takayuki, Nanmoku Koji, Goto Norihiko, Watarai Yoshihiko, Uchida Kazuharu, Morozumi Kunio, Kobayashi Takaaki

    CLINICAL TRANSPLANTATION   26 巻   頁: 43 - 48   2012年7月

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  33. Decay of polar cap patch

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

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

  34. 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

  35. 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

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

    Adachi Toru, Yamaoka Masashi, Yamamoto Mamoru, Otsuka Yuichi, Liu Huixin, Hsiao Chun-Chieh, Chen Alfred B., Hsu Rue-Ron

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

  37. 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

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

    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

  39. 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

  40. 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

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

    Hosokawa K., Kashimoto T., Suzuki S., Shiokawa K., Otsuka Y., Ogawa T.

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

  42. 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

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

    Balan N., Shiokawa K., Otsuka Y., Watanabe S., Bailey G. J.

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

  44. 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

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

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

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

    Yokoyama Tatsuhiro, Hysell David L., Otsuka Yuichi, Yamamoto Mamoru

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

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

    Suzuki S., Shiokawa K., Liu A. Z., Otsuka Y., Ogawa T., Nakamura T.

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

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  47. Equatorial GPS ionospheric scintillations over Kototabang, Indonesia and their relation to atmospheric waves from below

    Ogawa Tadahiko, Miyoshi Yasunobu, Otsuka Yuichi, Nakamura Takuji, Shiokawa Kazuo

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

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  48. Propagation characteristics of nighttime mesospheric and thermospheric waves observed by optical mesosphere thermosphere imagers at middle and low latitudes

    Shiokawa K., Otsuka Y., Ogawa T.

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

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

    Balan N., Alleyne H., Otsuka Y., Lekshmi D. Vijaya, Fejer B. G., McCrea I.

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

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  50. The Optical Mesosphere Thermosphere Imagers (OMTIs) for network measurements of aurora and airglow

    Shiokawa K., Hosokawa K., Sakaguchi K., Ieda A., Otsuka Y., Ogawa T., Connors M.

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

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

    Yokoyama T., Hysell D. L., Patra A. K., Otsuka Y., Yamamoto M.

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

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

    Otsuka Y., Ogawa T., Effendy

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

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  53. 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 S. E., Bychkov V. V., Shevtsov B. M.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A12 )   2008年12月

  54. Statistical study of relationship between medium-scale traveling ionospheric disturbance and sporadic E layer activities in summer night over Japan

    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

  55. Decay of 3-m-scale ionospheric irregularities associated with a plasma bubble observed with the Equatorial Atmosphere Radar

    Saito Susumu, Fukao Shoichiro, Yamamoto Mamoru, Otsuka Yuichi, Maruyama Takashi

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A11 )   2008年11月

  56. Simultaneous appearance of isolated auroral arcs and Pc 1 geomagnetic pulsations at subauroral latitudes

    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

  57. Daytime 150-km echoes observed with the Equatorial Atmosphere Radar in Indonesia: First results

    Patra A. K., Yokoyama T., Otsuka Y., Yamamoto M.

    GEOPHYSICAL RESEARCH LETTERS   35 巻 ( 6 )   2008年3月

  58. First three-dimensional simulation of the Perkins instability in the nighttime midlatitude ionosphere

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  59. Optical and Radio Observations and AMIE/TIEGCM Modeling of Nighttime Traveling Ionospheric Disturbances at Midlatitudes During Geomagnetic Storms

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  61. Medium-scale traveling ionospheric disturbances detected with dense and wide TEC maps over North America

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  62. Summer-winter hemispheric asymmetry of the sudden increase in ionospheric total electron content and of the O/N-2 ratio: Solar activity dependence

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  64. Simultaneous observations of nighttime medium-scale traveling ionospheric disturbances and E region field-aligned irregularities at midlatitude

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  65. Ground observation and AMIE-TIEGCM modeling of a storm-time traveling ionospheric disturbance

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  68. Medium-scale traveling ionospheric disturbances observed by GPS receiver network in Japan: a short review

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  72. Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada

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  78. Climatological study of GPS total electron content variations caused by medium-scale traveling ionospheric disturbances

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  90. Statistical characteristics of gravity waves observed by an all-sky imager at Darwin, Australia

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  94. A statistical study of large-scale traveling ionospheric disturbances using the GPS network in Japan

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  106. Annual and semiannual variations of the midlatitude ionosphere under low solar activity

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  107. Geomagnetic conjugate observations of equatorial airglow depletions

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  110. Imaging observations of the equatorward limit of midlatitude traveling ionospheric disturbances

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  111. Numerical simulation of gas flow through sand core

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  113. Plasmaspheric electron content in the GPS ray paths over Japan under magnetically quiet conditions at high solar activity

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  114. Observations of traveling ionospheric disturbances and 3-m scale irregularities in the nighttime F-region ionosphere with the MU radar and a GPS network

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  116. Three-channel imaging Fabry-Perot interferometer for measurement of mid-latitude airglow

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  119. Traveling ionospheric disturbances observed in the OI 630-nm nightglow images over Japan by using a multipoint imager network during the FRONT campaign

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

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    Okoh Daniel, Seemala Gopi, Rabiu Babatunde, Habarulema John Bosco, Jin Shuanggen, Shiokawa Kazuo, Otsuka Yuichi, Aggarwal Malini, Uwamahoro Jean, Mungufeni Patrick, Segun Bolaji, Obafaye Aderonke, Ellahony Nada, Okonkwo Chinelo, Tshisaphungo Mpho, Shetti Dadaso

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 12 ) 頁: 10512 - 10532   2019年12月

  136. 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

    Tsuchiya Satoshi, Shiokawa Kazuo, Fujinami Hatsuki, Otsuka Yuichi, Nakamura Takuji, Connors Martin, Schofield Ian, Shevtsov Boris, Poddelskiy Igor

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 10 ) 頁: 8110 - 8124   2019年10月

  137. 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

    Panasenko Sergii V, Otsuka Yuichi, van de Kamp Max, Chernogor Leonid F., Shinbori Atsuki, Tsugawa Takuya, Nishioka Michi

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

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

    Xu Heqiucen, Shiokawa Kazuo, Oyama Shin-ichiro, Otsuka Yuichi

    EARTH PLANETS AND SPACE   71 巻 ( 1 )   2019年8月

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

    Koval Artem, Chen Yao, Tsugawa Akuya, Otsuka Yuichi, Shinbori Atsuki, Nishioka Michi, Brazhenko Anatoliy, Stanislaysky Aleksander, Konovalenko Aleksander, Zhang Qing-He, Monstein Christian, Gorgutsa Roman

    ASTROPHYSICAL JOURNAL   877 巻 ( 2 )   2019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: 10.3847/1538-4357/ab1b52

    Web of Science

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

    Obana Yuki, Maruyama Naomi, Shinbori Atsuki, Hashimoto Kumiko K, 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

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   17 巻 ( 6 ) 頁: 861 - 876   2019年6月

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

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

    2019 URSI ASIA-PACIFIC RADIO SCIENCE CONFERENCE (AP-RASC)     頁: 18776063   2019年6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)  

    DOI: 10.23919/URSIAP-RASC.2019.8738444

    Web of Science

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

    Ratnam D. Venkata, Otsuka Yuichi, Sivavaraprasad G., Dabbakuti J. R. K. Kumar

    ADVANCES IN SPACE RESEARCH   63 巻 ( 9 ) 頁: 2848 - 2856   2019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: 10.1016/j.asr.2018.03.024

    Web of Science

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

    Sivavaraprasad G., Ratnam D. Venkata, Otsuka Yuichi

    JOURNAL OF NAVIGATION   72 巻 ( 3 ) 頁: 669 - 684   2019年5月

  144. 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

    Huang Fuqing, Otsuka Yuichi, Lei Jiuhou, Luan Xiaoli, Dou Xiankang, Li Guozhu

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 3 ) 頁: 2312 - 2322   2019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: 10.1029/2018JA026443

    Web of Science

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

    Moral Aysegul Ceren, Shiokawa Kazuo, Suzuki Shin, Liu Huixin, Otsuka Yuichi, Yatini Clara Yoko

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 3 ) 頁: 2198 - 2212   2019年3月

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

    Mallika, IL, Ratnam, DV, Ostuka, Y, Sivavaraprasad, G, Raman, S

    IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING   12 巻 ( 1 ) 頁: 371 - 381   2019年1月

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  147. Spatiotemporal development of pulsating auroral patch associated with discrete chorus elements: Arase and PWING observations

    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 R. C., Tanaka Y. -M., Nose M., Nagatsuma T., Connors M., Nishitani N., Hikishima M., Kumamoto A., Tsuchiya F., Kadokura A., Nishiyama T., Inoue T., Imamura K., Matsuoka A., Shinohara I.

    2019 URSI ASIA-PACIFIC RADIO SCIENCE CONFERENCE (AP-RASC)     2019年

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  148. 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

    Kurita, S, Miyoshi, Y, Shiokawa, K, Higashio, N, Mitani, T, Takashima, T, Matsuoka, A, Shinohara, I, Kletzing, CA, Blake, JB, Claudepierre, SG, Connors, M, Oyama, S, Nagatsuma, T, Sakaguchi, K, Baishev, D, Otsuka, Y

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 23 ) 頁: 12720 - 12729   2018年12月

  149. 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, Nose, 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

  150. 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 Yuki, Shiokawa Kazuo, Otsuka Yuichi, Connors Martin, Schofield Ian

    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

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

    Otsuka Yuichi

    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

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

    Figueiredo C. A. O. B., Takahashi H., Wrasse C. M., 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

  153. 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

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

    Shinbori Atsuki, Otsuka Yuichi, Tsugawa Takuya, Nishioka Michi, Kumamoto Atsushi, Tsuchiya Fuminori, Matsuda Shoya, Kasahara Yoshiya, Matsuoka Ayako, Ruohoniemi J. Michael, Shepherd Simon G, Nishitani Nozomu

    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

  155. 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

  156. 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 Satoshi, Shiokawa Kazuo, Fujinami Hatsuki, Otsuka Yuichi, Nakamura Takuji, Yamamoto Mamoru

    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

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

    Chaitanya P. Pavan, Patra A. K., 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

  158. 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

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

    Takahashi Hisao, Wrasse Cristiano Max, Oliveira Barros Figueiredo Cosme Alexandre, Barros Diego, Abdu Mangalathayil Ali, Otsuka Yuichi, Shiokawa Kazuo

    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

    Web of Science

    Scopus

  160. 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

  161. 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

  162. 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 Mamoru, Otsuka Yuichi, Jin Hidekatsu, Miyoshi Yasunobu

    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

  163. 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

    Web of Science

    Scopus

  164. 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 Hiroyuki, Jin Hidekatsu, Miyoshi Yasunobu, Fujiwara Hitoshi, Yokoyama Tatsuhiro, Otsuka Yuichi

    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

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

    Figueiredo C. A. O. B., Takahashi H., Wrasse C. M., 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

    Scopus

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

    Li Guozhu, Ning Baiqi, Abdu M. A., Wang Chi, Otsuka Yuichi, Wan Weixing, Lei Jiuhou, Nishioka Michi, Tsugawa Takuya, Hu Lianhuan, Yang Guotao, Yan Chunxiao

    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

    Web of Science

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

    M. Ozaki, K. Shiokawa, Y. Miyoshi, R. Kataoka, M. Connors, T. Inoue, S. Yagitani, Y. Ebihara, C. W. Jun, R. Nomura, K. Sakaguchi, Y. Otsuka, H. A. Uchida, I. Schofield, D. W. Danskin

    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)   出版者・発行元:Blackwell Publishing Ltd  

    Isolated proton aurora (IPA) is a manifestation of the wave-particle interaction visible at subauroral latitudes, with activity on many timescales. We herein present the first observational evidence of rapid luminous modulation of IPA correlated with simultaneously observed Pc1 waves observed on the ground, which are equivalent to the electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. The fastest luminous modulation of IPA was observed in the 1 Hz frequency range, which was twice the frequency of the related Pc1 waves. The time lag between variations of Pc1 wave power and the IPA luminosity suggests that the source regions of IPA are distributed near the magnetic equator, suggesting an EMIC wave-energetic (a few tens of keV) proton or relativistic (MeV or sub-MeV) electron interaction. The generation mechanism of this 1 Hz luminous modulation remains an open issue, but this study supports the importance of nonlinear pitch angle scattering via wave-particle interactions.

    DOI: 10.1002/2017GL076486

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  168. Spatial and Temporal Characteristics of Ionospheric Total Electron Content over Indian Equatorial and Low-Latitude GNSS Stations

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

    2018 CONFERENCE ON SIGNAL PROCESSING AND COMMUNICATION ENGINEERING SYSTEMS (SPACES)     頁: 105-108   2018年

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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

  169. Observations of Ultrawideband Signals in GPS TEC Variations over Europe during Solar Eclipse

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

    Shinbori Atsuki, Otsuka Yuichi, Tsugawa Takuya, Nishioka Michi, Kumamoto Atsushi, Tsuchia Fuminori, Matsuda Shoya, Kasahara Yoshiya

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

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  171. 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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  172. 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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  173. 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

    Daniel Okoh, Babatunde Rabiu, Kazuo Shiokawa, Yuichi Otsuka, Bolaji Segun, Elijah Falayi, Sylvester Onwuneme, Rafiat Kaka

    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)   出版者・発行元:Blackwell Publishing Ltd  

    This is the first paper that reports the occurrence frequency of equatorial plasma bubbles and their dependences of local time, season, and geomagnetic activity based on airglow imaging observations at West Africa. The all-sky imager, situated in Abuja (Geographic: 8.99°N, 7.38°E
    Geomagnetic: 1.60°S), has a 180° fisheye view covering almost the entire airspace of Nigeria. Plasma bubbles are observed for 70 nights of the 147 clear-sky nights from 9 June 2015 to 31 January 2017. Differences between nighttime and daytime ROTIs were also computed as a proxy of plasma bubbles using Global Navigation Satellite Systems (GNSS) receivers within the coverage of the all-sky imager. Most plasma bubble occurrences are found during equinoxes and least occurrences during solstices. The occurrence rate of plasma bubbles was highest around local midnight and lower for hours farther away. Most of the postmidnight plasma bubbles were observed around the months of December to March, a period that coincides with the harmattan period in Nigeria. The on/off status of plasma bubble in airglow and GNSS observations were in agreement for 67.2% of the total 768 h, while we suggest several reasons responsible for the remaining 32.8% when the airglow and GNSS bubble status are inconsistent. A majority of the plasma bubbles were observed under relatively quiet geomagnetic conditions (Dst ≥ −40 and Kp ≤ 3), but there was no significant pattern observed in the occurrence rate of plasma bubbles as a function of geomagnetic activity. We suggest that geomagnetic activities could have either suppressed or promoted the occurrence of plasma bubbles.

    DOI: 10.1002/2017JA024602

    Web of Science

    Scopus

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

    A. K. Patra, P. Pavan Chaitanya, J.‐P. St.‐Maurice, Y. Otsuka, T. Yokoyama, M. Yamamoto

    Geophysical Research Letters   44 巻 ( 22 ) 頁: 11,257 - 11,264   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)   出版者・発行元:American Geophysical Union ({AGU})  

    DOI: 10.1002/2017GL074678

    Web of Science

  175. 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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    Scopus

  176. 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

    D. Fukushima, K. Shiokawa, Y. Otsuka, M. Kubota, T. Yokoyama, M. Nishioka, S. Komonjinda, C. Y. Yatini

    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)   出版者・発行元:SPRINGER HEIDELBERG  

    DOI: 10.1186/s40623-017-0729-9

    Web of Science

  177. 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

    Kazuo Shiokawa, Yasuo Katoh, Yoshiyuki Hamaguchi, Yuka Yamamoto, Takumi Adachi, Mitsunori Ozaki, Shin-Ichiro Oyama, Masahito Nose, Tsutomu Nagatsuma, Yoshimasa Tanaka, Yuichi Otsuka, Yoshizumi Miyoshi, Ryuho Kataoka, Yuki Takagi, Yuhei Takeshita, Atsuki Shinbori, Satoshi Kurita, Tomoaki Hori, Nozomu Nishitani, Iku Shinohara, Fuminori Tsuchiya, Yuki Obana, Shin Suzuki, Naoko Takahashi, Kanako Seki, Akira Kadokura, Keisuke Hosokawa, Yasunobu Ogawa, Martin Connors, J. Michael Ruohoniemi, Mark Engebretson, Esa Turunen, Thomas Ulich, Jyrki Manninen, Tero Raita, Antti Kero, Arto Oksanen, Marko Back, Kirsti Kauristie, Jyrki Mattanen, Dmitry Baishev, Vladimir Kurkin, Alexey Oinats, Alexander Pashinin, Roman Vasilyev, Ravil Rakhmatulin, William Bristow, Marty Karjala

    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)   出版者・発行元:SPRINGER HEIDELBERG  

    The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron volts (MeV). These plasmas rotate around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV, and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphere using ground-based network observations, http://www.isee.nagoya-u.ac.jp/dimr/PWING/) has been carried out since April 2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers, 64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at subauroral latitudes (similar to 60 degrees geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been developed as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations with the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will contribute to the investigation of dynamical variation of particles and waves in the inner magnetosphere, which is one of the most important research topics in recent space physics, and the outcome of our research will improve safe and secure use of geospace around the Earth.

    DOI: 10.1186/s40623-017-0745-9

    Web of Science

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

    Shinbori Atsuki, Koyama Yukinobu, Nose Masahito, Hori Tomoaki, Otsuka Yuichi

    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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    Scopus

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

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

    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)   出版者・発行元:Wiley-Blackwell  

    DOI: 10.1002/2017JA024589

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  180. 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 Huixin, 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

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  181. 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 T. S., Ejiri M. K., 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

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

    D. Fukushima, K. Shiokawa, Y. Otsuka, M. Kubota, T. Yokoyama, M. Nishioka, S. Komonjinda, C. Y. Yatini

    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)   出版者・発行元:SPRINGER HEIDELBERG  

    We conducted geomagnetically conjugate observations of 630-nm airglow for a midnight brightness wave (MBW) at Kototabang, Indonesia [geomagnetic latitude (MLAT): 10.0 degrees S], and Chiang Mai, Thailand (MLAT: 8.9 degrees N), which are geomagnetically conjugate points at low latitudes. An airglow enhancement that was considered to be an MBW was observed in OI (630-nm) airglow images at Kototabang around local midnight from 2240 to 2430 LT on February 7, 2011. This MBW propagated south-southwestward, which is geomagnetically poleward, at a velocity of 290 m/s. However, a similar wave was not observed in the 630-nm airglow images at Chiang Mai. This is the first evidence of an MBW that does not have geomagnetic conjugacy, which also implies generation of MBW only in one side of the hemisphere from the equator. We simultaneously observed thermospheric neutral winds observed by a co-located Fabry-Perot interferometer at Kototabang. The observed meridional winds turned from northward (geomagnetically equatorward) to southward (geomagnetically poleward) just before the wave was observed. This indicates that the observed MBW was generated by the poleward winds which push ionospheric plasma down along geomagnetic field lines, thereby increasing the 630-nm airglow intensity. The bottomside ionospheric heights observed by ionosondes rapidly decreased at Kototabang and slightly increased at Chiang Mai. We suggest that the polarization electric field inside the observed MBW is projected to the northern hemisphere, causing the small height increase observed at Chiang Mai. This implies that electromagnetic coupling between hemispheres can occur even though the original disturbance is caused purely by the neutral wind.

    DOI: 10.1186/s40623-017-0698-z

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  183. 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

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

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

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We investigated a postmidnight field-aligned irregularity (FAI) event observed with the Equatorial Atmosphere Radar at Kototabang (0.2 degrees S, 100.3 degrees E, dip latitude 10.4 degrees S) in Indonesia on the night of 9 July 2010 using a comprehensive data set of both neutral and plasma parameters. We examined the rate of total electron content change index (ROTI) obtained from GPS receivers in Southeast Asia, airglow images detected by an all-sky imager, and thermospheric neutral winds and temperatures obtained by a Fabry-Perot interferometer at Kototabang. Altitudes of the F layer (h'F) observed by ionosondes at Kototabang, Chiang Mai, and Chumphon were also surveyed. We found that the postmidnight FAIs occurred within plasma bubbles and coincided with kilometer-scale plasma density irregularities. We also observed an enhancement of the magnetically equatorward thermospheric neutral wind at the same time as the increase of h'F at low-latitude stations, but h'F at a station near the magnetic equator remained invariant. Simultaneously, a magnetically equatorward gradient of thermospheric temperature was identified at Kototabang. The convergence of equatorward neutral winds from the Northern and Southern Hemispheres could be associated with a midnight temperature maximum occurring around the magnetic equator. Equatorward neutral winds can uplift the F layer at low latitudes and increase the growth rate of Rayleigh-Taylor instabilities, causing more rapid extension of plasma bubbles. The equatorward winds in both hemispheres also intensify the eastward Pedersen current, so a large polarization electric field generated in the plasma bubble might play an important role in the generation of postmidnight FAIs.

    DOI: 10.1002/2017JA024048

    Web of Science

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

    Buhari Suhaila M., Abdullah Mardina, Otsuka Yuichi, Yokoyama Tatsuhiro, Nishioka Michi, Hasbi Alina Marie, Tsugawa Takuya

    SAINS MALAYSIANA   46 巻 ( 6 ) 頁: 879 - 885   2017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: 10.17576/jsm-2017-4606-06

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  186. 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 C. A. O. B., Wrasse C. M., 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

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

    Y. Nakamura, K. Shiokawa, Y. Otsuka, S. Oyama, S. Nozawa, T. Komolmis, S. Komonjida, Dave Neudegg, Colin Yuile, J. Meriwether, H. Shinagawa, H. Jin

    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)   出版者・発行元:SPRINGER HEIDELBERG  

    Fabry-Perot interferometer (FPI) is an instrument that can measure the temperature and wind velocity of the thermosphere through observations of airglow emission at a wavelength of 630.0 nm. The Solar-Terrestrial Environment Laboratory/Institute for Space-Earth Environmental Research, Nagoya University, has recently developed four new ground-based FPIs. One of those FPIs, possessing a large-aperture etalon (diameter: 116 mm), was installed in Tromso (FP01), Norway, in 2009. The other three small FPIs, using 70-mm-diameter etalons, were installed in Thailand (FP02), Indonesia (FP03) and Australia (FP04) in 2010-2011. They use highly sensitive cooled-CCD cameras with 1024 x 1024 pixels to obtain interference fringes. However, appropriate temperature has not been obtained from the interference fringes using these new small-aperture FPIs. In the present study we improved the analysis procedure of temperature determination using these FPIs. Each of FPIs measures north, south, east and west directions repeatedly by rotating two mirrors mounted on top of the FPI. We estimated center pixel of laser fringe and airglow fringes for each direction and found significant differences in the center pixel locations (a few pixels) among the measurement directions. These differences are considered to be caused by movement of the scanning mirror on the top of the optics, resulting in mechanical distortion of the optics body. By calculating the fringe center separately for each direction, we could correct these center pixel variations and determine the temperature with random errors of 10-40 K. This new method was employed to the all measurements from four FPIs after 2009 and provided temperatures with reasonably small errors. However, we found that temperatures below 400 K were obtained associated with weak airglow intensities and concluded using a model calculation that they are due to contamination of OH line emissions in the upper mesosphere. By defining an appropriate threshold of the fringe peak count, we successfully eliminated these unrealistic temperature values, and the corrected temperature values became comparable to those provided by the MSIS-90E and GAIA models.

    DOI: 10.1186/s40623-017-0643-1

    Web of Science

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

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

  189. STATISTICAL ANALYSIS OF THE OCCURRENCES OF MSTIDs OBSERVED BY ALL-SKY IMAGER IN LOW MAGNETIC LATITUDE

    Ednofri, Wu Falin, Otsuka Yuichi, Ishii Mamoru, Marlia Dessi, Zhao Yan

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

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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

  190. On the effect of thermospheric neutral winds on post-midnight field-aligned irregularities at low latitudes

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

    2017 XXXIIND GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM OF THE INTERNATIONAL UNION OF RADIO SCIENCE (URSI GASS)     2017年

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

    Nishino Masaki N., Shiokawa Kazuo, Otsuka Yuichi

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.icarus.2016.08.004

    Web of Science

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

    Takahashi H., Wrasse C. M., Denardini C. M., Padua M. B., de Paula E. R., Costa S. M. A., Otsuka Y., Shiokawa K., Galera Monico J. F., 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016SW001474

    Web of Science

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

    S. Perwitasari, T. Sakanoi, T. Nakamura, M. K. Ejiri, M. Tsutsumi, Y. Tomikawa, Y. Otsuka, A. Yamazaki, A. Saito

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We report a statistical study on concentric gravity waves (CGWs) in the mesopause (similar to 95 km) using 3 years nightglow data obtained by Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere/Visible and near-Infrared Spectral Imager. The 235 CGWs events were found with horizontal wavelength ranging from 40 to 250 km and maximum radius of 200 to 3000 km. The latitudinal distribution of the CGWs centers had peaks in mid latitude (40 degrees N and 40 degrees S) and minimum at low latitudes (10 degrees S). More events were found in the summer hemisphere midlatitudes, with a rapid transition between northern and Southern Hemisphere around the equinoxes. The occurrence probability was significantly higher during nonsolstice months (February-May and August-November) than solstice months (June-July and December-January), suggesting that there was a little breaking or critical level absorption so the waves could reach the mesopause more often during these periods. The global distribution showed several preferable regions but very few events over tropical convective regions.

    DOI: 10.1002/2016GL071511

    Web of Science

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

    Ajith K. K., Ram S. Tulasi, 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2016JA023024

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

    M. Ozaki, K. Shiokawa, Y. Miyoshi, R. Kataoka, S. Yagitani, T. Inoue, Y. Ebihara, C. -W Jun, R. Nomura, K. Sakaguchi, Y. Otsuka, M. Shoji, I. Schofield, M. Connors, V. K. Jordanova

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    To understand the role of electromagnetic ion cyclotron (EMIC) waves in determining the temporal features of pulsating proton aurora (PPA) via wave-particle interactions at subauroral latitudes, high-time-resolution (1/8s) images of proton-induced N-2(+) emissions were recorded using a new electron multiplying charge-coupled device camera, along with related Pc1 pulsations on the ground. The observed Pc1 pulsations consisted of successive rising-tone elements with a spacing for each element of 100s and subpacket structures, which manifest as amplitude modulations with a period of a few tens of seconds. In accordance with the temporal features of the Pc1 pulsations, the auroral intensity showed a similar repetition period of 100s and an unpredicted fast modulation of a few tens of seconds. These results indicate that PPA is generated by pitch angle scattering, nonlinearly interacting with Pc1/EMIC waves at the magnetic equator.

    DOI: 10.1002/2016GL070008

    Web of Science

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

    Guozhu Li, Yuichi Otsuka, Baiqi Ning, M. A. Abdu, M. Yamamoto, Weixing Wan, Libo Liu, Prayitno Abadi

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    A close link between the atmospheric Intertropical Convergence Zone (ITCZ) and ionospheric plasma bubble has been proposed since the last century. But this relationship has often appeared to be less than convincing due to the simultaneous roles played by several other factors in shaping the global distribution of ionospheric bubbles. From simultaneous collaborative radar multibeam steering measurements at Kototabang (0.2 degrees S, 100.3 degrees E) and Sanya (18.4 degrees N, 109.6 degrees E), conducted during September-October of 2012 and 2013, we find that the total numbers of nights with bubble (i.e., occurrence rates) at the two closely located longitudes (Kototabang and Sanya) are comparable. But interestingly, the total number of nights with locally generated bubble (i.e., generation rate) over Kototabang is clearly more than that over Sanya. Further analysis reveals that a more active ITCZ is situated around the longitude of Kototabang. We surmise that the enhanced ionospheric bubble generation at Kototabang longitude could be caused by a higher gravity wave activity associated with the more active ITCZ.

    DOI: 10.1002/2016GL068145

    Web of Science

  198. 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

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

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

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We found rising tone emissions with a dispersion of approximate to 1Hz per several tens of seconds in the dynamic spectrum of a Pc1 geomagnetic pulsation (Pc1) observed on the ground. These Pc1 rising tones were successively observed over approximate to 30min from 0250UT on 14 October 2006 by an induction magnetometer at Athabasca, Canada (54.7 degrees N, 246.7 degrees E, magnetic latitude 61.7 degrees N). Simultaneously, a Time History of Events and Macroscale Interactions during Substorms panchromatic (THEMIS) all-sky camera detected pulsations of an isolated proton aurora with a period of several tens of seconds, approximate to 10% variations in intensity, and fine structures of 3 degrees in magnetic longitudes. The pulsations of the proton aurora close to the zenith of ATH have one-to-one correspondences with the Pc1 rising tones. This suggests that these rising tones scatter magnetospheric protons intermittently at the equatorial region. The radial motion of the magnetospheric source, of which the isolated proton aurora is a projection, can explain the central frequency increase of Pc1, but not the shorter period (tens of seconds) frequency increase of approximate to 1Hz in Pc1 rising tones. We suggest that EMIC-triggered emissions generate the frequency increase of Pc1 rising tones on the ground and that they also cause the Pc1 pearl structure, which has a similar characteristic time.

    DOI: 10.1002/2015JA021681

    Web of Science

  200. 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

    S. Tulasi Ram, T. Yokoyama, Y. Otsuka, K. Shiokawa, S. Sripathi, B. Veenadhari, R. Heelis, K. K. Ajith, V. S. Gowtam, S. Gurubaran, P. Supnithi, M. Le Huy

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The equatorial zonal electric field responses to prompt penetration of eastward convection electric fields (PPEF) were compared at closely spaced longitudinal intervals at dusk to premidnight sectors during the intense geomagnetic storm of 17 March 2015. At dusk sector (Indian longitudes), a rapid uplift of equatorial F layer to >550km and development of intense equatorial plasma bubbles (EPBs) were observed. These EPBs were found to extend up to 27.13 degrees N and 25.98 degrees S magnetic dip latitudes indicating their altitude development to similar to 1670km at apex. In contrast, at few degrees east in the premidnight sector (Thailand-Indonesian longitudes), no significant height rise and/or EPB activity has been observed. The eastward electric field perturbations due to PPEF are greatly dominated at dusk sector despite the existence of background westward ionospheric disturbance dynamo (IDD) fields, whereas they were mostly counter balanced by the IDD fields in the premidnight sector. In situ observations from SWARM-A and SWARM-C and Communication/Navigation Outage Forecasting System satellites detected a large plasma density depletion near Indian equatorial region due to large electrodynamic uplift of F layer to higher than satellite altitudes. Further, this large uplift is found to confine to a narrow longitudinal sector centered on sunset terminator. This study brings out the significantly enhanced equatorial zonal electric field in response to PPEF that is uniquely confined to dusk sector. The responsible mechanisms are discussed in terms of unique electrodynamic conditions prevailing at dusk sector in the presence of convection electric fields associated with the onset of a substorm under southward interplanetary magnetic field B-z.

    DOI: 10.1002/2015JA021932

    Web of Science

  201. 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

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

    Jonah O. F., de Paula E. R., Muella M. T. A. H., Dutra S. L. G., Kherani E. A., Negreti P. M. S., Otsuka Y.

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2015.10.005

    Web of Science

  203. 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

    Mitsunori Ozaki, Satoshi Yagitani, Kaoru Sawai, Kazuo Shiokawa, Yoshizumi Miyoshi, Ryuho Kataoka, Akimasa Ieda, Yusuke Ebihara, Martin Connors, Ian Schofield, Yuto Katoh, Yuichi Otsuka, Naoki Sunagawa, Vania K. Jordanova

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    A correlation was observed between chorus emissions and pulsating aurora (PA) from observations at Athabasca (L approximate to 4.3) in Canada at 9: 00-9: 20 UT on 7 February 2013, using an electron multiplying charge-coupled device camera and a VLF loop antenna with sampling rates of 110 Hz and 100 kHz, respectively. Pulsating aurora having a quasiperiodic variation in luminosity and a few hertz modulation was observed together with chorus emissions consisting of a group of successive rising-tone elements. The repetition period and modulation frequency of the PA are in good agreement with those of the modulated chorus. After 9: 11 UT, the temporal features of the aurora became aperiodic PA of indistinct modulation. Simultaneously, the rising-tone chorus turned into chorus emissions consisting of numerous rising-tone elements. The equatorial geomagnetic field inhomogeneity calculated using the Tsyganenko 2002 model shows a decreasing trend during the period. This result is consistent with nonlinear wave growth theory having a small geomagnetic field inhomogeneity, which contributes to a decrease in the threshold amplitude to trigger discrete chorus elements. These observations show a close connection between chorus emissions and PA on timescales from milliseconds for generation of discrete chorus elements on the microphysics of wave-particle interaction to minutes for the variations of the geomagnetic field inhomogeneity related with the substorm activity.

    DOI: 10.1002/2015JA021381

    Web of Science

  204. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021424

    Web of Science

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

    Thomas E. G., Hosokawa K., Sakai J., Baker J. B. H., Ruohoniemi J. M., Taguchi S., Shiokawa K., Otsuka Y., Coster A. J., St.-Maurice J. -P., McWilliams K. A.

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015RS005672

    Web of Science

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

    Takahashi H., Wrasse C. M., Otsuka Y., Ivo A., Gomes V., Paulino I., Medeiros A. F., Denardini C. M., 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2015.06.003

    Web of Science

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

    Hashimoto Ayumi, Shiokawa Kazuo, Otsuka Yuichi, Oyama Shin-ichiro, Nozawa Satonori, Hori Tomoaki, Lester Mark, Johnsen Magnar Gullikstad

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021000

    Web of Science

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

    Ram S. Tulasi, Ajith K. K., 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2015JA021427

    Web of Science

  209. 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 Prayitno, Otsuka Yuichi, Tsugawa Takuya

    EARTH PLANETS AND SPACE   67 巻   2015年5月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-015-0246-7

    Web of Science

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

    Shiokawa Kazuo, Otsuka Yuichi, Lynn Kenneth J. W., Wilkinson Philip, Tsugawa Takuya

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-015-0202-6

    Web of Science

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

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

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    This is the first paper that reports simultaneous observations of zonal drift of plasma bubbles and the thermospheric neutral winds at geomagnetically conjugate points in both hemispheres. The plasma bubbles were observed in the 630nm nighttime airglow images taken by using highly sensitive all-sky airglow imagers at Kototabang, Indonesia (geomagnetic latitude (MLAT): 10.0 degrees S), and Chiang Mai, Thailand (MLAT: 8.9 degrees N), which are nearly geomagnetically conjugate stations, for 7h from 13 to 20UT (from 20 to 03LT) on 5 April 2011. The bubbles continuously propagated eastward with velocities of 100-125m/s. The 630nm images at Chiang Mai and those mapped to the conjugate point of Kototabang fit very well, which indicates that the observed plasma bubbles were geomagnetically connected. The eastward thermospheric neutral winds measured by two Fabry-Perot interferometers were 70-130m/s at Kototabang and 50-90m/s at Chiang Mai. We compared the observed plasma bubble drift velocity with the velocity calculated from the observed neutral winds and the model conductivity, to investigate the F region dynamo contribution to the bubble drift velocity. The estimated drift velocities were 60-90% of the observed velocities of the plasma bubbles, suggesting that most of the plasma bubble velocity can be explained by the F region dynamo effect.

    DOI: 10.1002/2014JA020398

    Web of Science

  212. 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 K. K., Ram S. Tulasi, Yamamoto M., Yokoyama T., Gowtam V. Sai, 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020878

    Web of Science

  213. 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)  

  214. 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

  215. 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

  216. 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

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

    Shinbori Atsuki, Koyama Yukinobu, Nose Masahito, Hori Tomoaki, Otsuka Yuichi, Yatagai Akiyo

    EARTH PLANETS AND SPACE   66 巻   2014年12月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-014-0155-1

    Web of Science

  218. CME front and severe space weather 査読有り

    N. Balan, R. Skoug, S. Tulasi Ram, P. K. Rajesh, K. Shiokawa, Y. Otsuka, I. S. Batista, Y. Ebihara, T. Nakamura

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Thanks to the work of a number of scientists who made it known that severe space weather can cause extensive social and economic disruptions in the modern high-technology society. It is therefore important to understand what determines the severity of space weather and whether it can be predicted. We present results obtained from the analysis of coronal mass ejections (CMEs), solar energetic particle (SEP) events, interplanetary magnetic field (IMF), CME-magnetosphere coupling, and geomagnetic storms associated with the major space weather events since 1998 by combining data from the ACE and GOES satellites with geomagnetic parameters and the Carrington event of 1859, the Quebec event of 1989, and an event in 1958. The results seem to indicate that (1) it is the impulsive energy mainly due to the impulsive velocity and orientation of IMF B-z at the leading edge of the CMEs (or CME front) that determine the severity of space weather. (2) CMEs having high impulsive velocity (sudden nonfluctuating increase by over 275 km s(-1) over the background) caused severe space weather (SvSW) in the heliosphere (failure of the solar wind ion mode of Solar Wind Electron Proton Alpha Monitor in ACE) probably by suddenly accelerating the high-energy particles in the SEPs ahead directly or through the shocks. (3) The impact of such CMEs which also show the IMF B-z southward from the leading edge caused SvSW at the Earth including extreme geomagnetic storms of mean Dst(MP) < -250 nT during main phases, and the known electric power outages happened during some of these SvSW events. (4) The higher the impulsive velocity, the more severe the space weather, like faster weather fronts and tsunami fronts causing more severe damage through impulsive action. (5) The CMEs having IMF B-z northward at the leading edge do not seem to cause SvSW on Earth, although, later when the IMF B-z turns southward, they can lead to super geomagnetic storms of intensity (Dst(min)) less than even -400 nT.

    DOI: 10.1002/2014JA020151

    Web of Science

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

    Buhari S. M., Abdullah M., Hasbi A. M., 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020433

    Web of Science

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

    Narayanan V. Lakshmi, 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020368

    Web of Science

  221. Auroral fragmentation into patches 査読有り

    Kazuo Shiokawa, Ayumi Hashimoto, Tomoaki Hori, Kaori Sakaguchi, Yasunobu Ogawa, Eric Donovan, Emma Spanswick, Martin Connors, Yuichi Otsuka, Shin-Ichiro Oyama, Satonori Nozawa, Kathryn McWilliams

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Auroral patches in diffuse auroras are very common features in the postmidnight local time. However, the processes that produce auroral patches are not yet well understood. In this paper we present two examples of auroral fragmentation which is the process by which uniform aurora is broken into several fragments to form auroral patches. These examples were observed at Athabasca, Canada (geomagnetic latitude: 61.7 degrees N), and TromsO, Norway (67.1 degrees N). Captured in sequences of images, the auroral fragmentation occurs as finger-like structures developing latitudinally with horizontal-scale sizes of 40-100 km at ionospheric altitudes. The structures tend to develop in a north-south direction with speeds of 150-420 m/s without any shearing motion, suggesting that pressure-driven instability in the balance between the earthward magnetic-tension force and the tailward pressure gradient force in the magnetosphere is the main driving force of the auroral fragmentation. Therefore, these observations indicate that auroral fragmentation associated with pressure-driven instability is a process that creates auroral patches. The observed slow eastward drift of aurora during the auroral fragmentation suggests that fragmentation occurs in low-energy ambient plasma.

    DOI: 10.1002/2014JA020050

    Web of Science

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

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

    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)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Spaceborne imagers are able to observe the airglow structures with wide field of views regardless of the tropospheric condition that limits the observational time of the ground-based imagers. Concentric wave structures of the O-2 airglow in 762 nm wavelength were observed over North America on 1 June 2013 from the International Space Station. This was the first observation in which the entire image of the structure was captured from space, and its spatial scale size was determined to be 1200 km radius without assumptions. The apparent horizontal wavelength was 80 km, and the amplitude in the intensity was approximately 20% of the background intensity. The propagation velocity of the structure was derived as 125 +/- 62 m/s and atmospheric gravity waves were estimated to be generated for 3. 5 +/- 1. 7 h. Concentric structures observed in this event were interpreted to be generated by super cells that caused a tornado in its early phase.

    DOI: 10.1002/2014GL061403

    Web of Science

  223. 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 J. F. G., Paula E., Nogueira P., Denardini C. M., Becker-Guedes F., Wrasse C. M., Ivo A. S., Gomes V. C. F., Gargarela W. Jr., Sant'Anna N., Gatto R.

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.asr.2014.01.032

    Web of Science

  224. 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)  

  225. 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

  226. 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

  227. 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)  

  228. 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

  229. 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)  

  230. 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)  

  231. 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

  232. 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

  233. 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)  

  234. 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

  235. 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

  236. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2013GL057627

    Web of Science

  237. 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

  238. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2013.03.024

    Web of Science

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

    Lynn K. J. W., Otsuka Y., Shiokawa K.

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2013.03.020

    Web of Science

  240. 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 J. Y., Bailey G. J.

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/jgra.50275

    Web of Science

    Scopus

  241. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2012GL054605

    Web of Science

    Scopus

  242. 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

  243. 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

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  244. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-31-163-2013

    Web of Science

  245. 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

     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 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

  246. 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)  

  247. 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

  248. 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

  249. 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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  250. 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

  251. 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

  252. 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

  253. 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

  254. 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

  255. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2012GL052286

    Web of Science

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

    Makela Jonathan J., Otsuka Yuichi

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

  257. 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

  258. 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)  

  259. 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

  260. 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

  261. 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

  262. 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

  263. 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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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2012.05.004

    Web of Science

  264. 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

  265. 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

  266. 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

  267. 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

  268. 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

  269. 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

  270. 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

  271. 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

  272. 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

  273. 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

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

    Lynn K. J. W., Otsuka Y., Shiokawa K.

    GEOPHYSICAL RESEARCH LETTERS   38 巻   2011年12月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2011GL049856

    Web of Science

  275. 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

  276. 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

  277. 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

  278. 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

  279. 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

  280. 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

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

    Adachi Toru, Otsuka Yuichi, Yamaoka Masashi, Yamamoto Mamoru, Shiokawa Kazuo, Chen Alfred B., Hsu Rue-Ron

    GEOPHYSICAL RESEARCH LETTERS   38 巻   2011年2月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010GL046268

    Web of Science

  282. 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

  283. 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

  284. 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

  285. 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

    A. Saito, T. Tsugawa, Y. Otsuka, M. Nishioka, T. Iyemori, M. Matsumura, S. Saito, C. H. Chen, Y. Goi, N. Choosakul

    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)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    Two-dimensional structures of the ionospheric variations generated by the acoustic resonance between the ground surface and the lower thermosphere was observed for the first time near the epicenter after the M 9.0 Tohoku earthquake on March 11, 2011. A short-period oscillation of total electron content was observed by a GPS receiver array after the earthquake for four hours in the vicinity of the epicenter. It was centered in the east of the epicenter where the tsunami was estimated to commence. The frequency of the dominant mode of the oscillation was 4.5 mHz, 222 seconds of period, while there were minor oscillations whose frequency were 3.7 mHz and 5.3 mHz. These periods are consistent with the periods of the acoustic resonance between the ground surface and the lower thermosphere, predicted by a numerical model. The amplitude of the TEC oscillation showed a gradual change of the amplitude. The two-dimensional distributions of TEC variations generated by this resonance had wave frontal structures that extended from northwest to southeast. The resonant oscillation of the TEC was accompanied by a depletion of TEC whose duration was about 60 minutes. The area of this depletion also centered on the epicenter.

    DOI: 10.5047/eps.2011.06.034

    Web of Science

  286. 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

     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  

    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

  287. 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

     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  

    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

  288. 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

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1541/ieejfms.131.983

  289. 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

  290. 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)  

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

    Chen C. H., Saito A., Lin C. H., Liu J. Y., Tsai H. F., 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

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.026

    Web of Science

  292. 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

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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)  

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

    Maruyama Takashi, Tsugawa Takuya, Kato Hisao, Saito Akinori, Otsuka Yuichi, Nishioka Michi

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

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.008

    Web of Science

  294. 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 K. T.

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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.06.035

    Web of Science

  295. 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 C. H.

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

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.07.015

    Web of Science

  296. 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 Nozomu, Ogawa Tadahiko, Otsuka Yuichi, Hosokawa Keisuke, Hori Tomoaki

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

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2011.07.003

    Web of Science

  297. 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

  298. 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

  299. 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

  300. 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

     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  

    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

  301. 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

     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  

    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

  302. 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

  303. 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

     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  

    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

  304. Nighttime-like quasi periodic echoes induced by a partial solar eclipse 査読有り

    Thampi Smitha V., Yamamoto Mamoru, Liu Huixin, Saito Susumu, Otsuka Yuichi, Patra Amit Kumar

    GEOPHYSICAL RESEARCH LETTERS   37 巻   2010年5月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010GL042855

    Web of Science

  305. 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

  306. 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

  307. 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

  308. 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

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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  

    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

  309. 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

  310. 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

  311. 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 T. T., Nozawa S., Ogawa Y., Otsuka Y., Watkins B. J.

    ANNALES GEOPHYSICAE   28 巻 ( 10 ) 頁: 1847 - 1857   2010年

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-28-1847-2010

    Web of Science

  312. Longitudinal development of low-latitude ionospheric irregularities during the geomagnetic storms of July 2004 査読有り

    Guozhu Li, Baiqi Ning, Lianhuan Hu, Libo Liu, Xinan Yue, Weixing Wan, Biqiang Zhao, K. Igarashi, Minoru Kubota, Yuichi Otsuka, J. S. Xu, J. Y. Liu

    Journal of Geophysical Research: Space Physics   115 巻 ( 4 )   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  

    During the period 22-28 July 2004, three geomagnetic storms occurred due to a sequence of coronal mass ejections. In this paper we present and discuss the ionospheric observations from a set of in situ satellites and ground-based GPS total electron content and scintillation receivers, a VHF radar, and two chains of ionosondes (∼300°E and ∼120°E, respectively) that provide the evolutionary characteristics of equatorial and low-latitude ionospheric irregularities versus longitude during these storm periods. It is found that the irregularities occurred over a wide longitudinal range, extending from around 300°E to 120°E on storm days 25 and 27 July 2004. On 25 July plasma bubbles (PBs) began premidnight in America and postmidnight in Southeast Asia. On 27 July the occurrence of irregularities followed the sunset terminator and was observed sequentially after sunset from American to Southeast Asian longitudes. Past studies have reported that storm-time low-latitude ionospheric irregularities are mostly confined to a narrower longitude range, &lt
    90°, after sunset hours and are associated with the prompt penetration of eastward electric fields (PPEFs) into low latitudes. In June solstice months the occurrence of range-type spread F or PBs is very low in Southeast Asian and South American sectors. In contrast, the present results indicate that geomagnetic storms triggered the wide longitudinal development of PBs. In the American sector this was probably due to the effects of PPEFs on both storm days. However, in the Southeast Asian sector the PBs on the 2 days probably arose from disturbance dynamo electric field (DDEF), PPEF, and gravity wave seeding effects. This study further shows that under complex storm conditions, besides the long duration or multiple penetrations, the combined effects of PPEFs and DDEFs could result in a wide longitude extent of ionospheric irregularities at times. © 2010 by the American Geophysical Union.

    DOI: 10.1029/2009JA014830

    Web of Science

    Scopus

  313. 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

  314. 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 B. M., Smirnov S., Poddelsky I., Connors M.

    EARTH PLANETS AND SPACE   62 巻 ( 6 ) 頁: 517 - 524   2010年

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2010.05.003

    Web of Science

  315. 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)  

  316. Thermospheric temperature and density variations 査読有り

    Fujiwara Hitoshi, Miyoshi Yasunobu, Jin Hidekatsu, Shinagawa Hiroyuki, Otsuka Yuichi, Saito Akinori, Ishii Mamoru

    SOLAR AND STELLAR VARIABILITY: IMPACT ON EARTH AND PLANETS   ( 264 ) 頁: 310 - +   2010年

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    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

  317. Ionospheric and geomagnetic disturbances during the 2005 Sumatran earthquakes 査読有り

    Hasbi Alina Marie, Momani Mohammed Awad, Ali Mohd Alauddin Mohd, Misran Norbahiah, Shiokawa Kazuo, Otsuka Yuichi, Yumoto Kiyohumi

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   71 巻 ( 17-18 ) 頁: 1992 - 2005   2009年12月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2009.09.004

    Web of Science

  318. 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

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2009.08.004

    Web of Science

  319. 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 Smitha V., Yamamoto Mamoru, Tsunoda Roland T., Otsuka Yuichi, Tsugawa Takuya, Uemoto Jyunpei, Ishii Mamoru

    GEOPHYSICAL RESEARCH LETTERS   36 巻   2009年9月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009GL039887

    Web of Science

  320. 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 T. F, Koustov A. V, Shevtsov B. M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年7月

  321. First simultaneous observations of daytime MSTIDs over North America using GPS-TEC and DEMETER satellite data 査読有り

    Onishi Tatsuo, Tsugawa Takuya, Otsuka Yuichi, Berthelier Jean-Jacques, Lebreton Jean-Pierre

    GEOPHYSICAL RESEARCH LETTERS   36 巻   2009年6月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009GL038156

    Web of Science

  322. 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

  323. 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

  324. 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

  325. 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

  326. 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 M. R.

    GEOPHYSICAL RESEARCH LETTERS   36 巻   2009年4月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009GL037512

    Web of Science

  327. 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

  328. 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

    Y. Sahai, F. Becker-Guedes, P. R. Fagundes, R. De Jesus, A. J. De Abreu, Y. Otsuka, K. Shiokawa, K. Igarashi, K. Yumoto, C. S. Huang, H. T. Lan, A. Saito, F. L. Guarnieri, V. G. Pillat, J. A. Bittencourt

    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  

    The Sun was very active in the early part of November 2004. During the period of 8-10 November 2004, intense geomagnetic disturbances with two superstorms were observed. In a companion paper (hereinafter referred to as paper 1), the effects observed in the F region during the intense geomagnetic disturbances in the early part of November 2004 in the Latin American sector were presented. In the present paper, we investigate the effects observed in the F region during the intense geomagnetic disturbances in the early part of November 2004 in the east Asian sector. We have used the ionospheric sounding observations at Ho Chi Minh City (Vietnam) and Okinawa, Yamagawa, Kokubunji, and Wakkanai (Japan) in the present investigations. Also, GPS observations in the east Asian sector (several longitude zones) have been used to study the effect in the F region during the intense geomagnetic disturbances. The ion density versus latitudinal variations obtained by the DMSP F15 satellite orbiting at about 800 km altitude in the east Asian sector and the magnetic field data obtained at several stations in the Japanese meridian are also presented. Several important features from these observations in both the sectors during this extended period of intense geomagnetic disturbances are presented. The east Asian sector showed very pronounced effects during the second superstorm, which was preceded by two storm enhancements. It should be mentioned that around the beginning of the night on 10 November, ionospheric irregularities propagating from higher midlatitude region to low-latitude region were observed in the Japanese sector. The most intense geomagnetic field H component in that sector was observed on 10 November at L = 2.8, indicating that the auroral oval and the heating got further to low latitudes and the ionospheric irregularities observed in the Japanese sector on this night are midlatitude ionospheric disturbances associated with the second superstorm. The absence of ionospheric irregularities in the Japanese sector during the 8 November superstorm suggests that the magnetosphere-ionosphere system was possibly preconditioned (primed) when the second interplanetary structure impacted the magnetosphere. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013053

    Scopus

  329. 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

  330. 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

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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  

    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

  331. 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

  332. 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

  333. 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

  334. 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

  335. 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

  336. Medium-Scale Traveling Ionospheric Disturbances and Plasma Bubbles Observed by an All-Sky Airglow Imager at Yonaguni, Japan 査読有り

    Ogawa Tadahiko, Otsuka Yuichi, Shiokawa Kazuo, Tsugawa Takuya, Saito Akinori, Hoshinoo Kazuaki, Matunaga Keisuke, Kubota Minoru, Ishii Mamoru

    TERRESTRIAL ATMOSPHERIC AND OCEANIC SCIENCES   20 巻 ( 1 ) 頁: 287 - 295   2009年2月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.3319/TAO.2007.12.06.02(F3C)

    Web of Science

  337. 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 (< 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

  338. 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

     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: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

  339. Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 'Halloween Storms' 査読有り

    Y. Sahai, F. Becker-Guedes, P. R. Fagundes, A. J. de Abreu, R. de Jesus, V. G. Pillat, J. R. Abalde, C. R. Martinis, C. Brunini, M. Gende, C. -S. Huang, X. Pi, W. L. C. Lima, J. A. Bittencourt, Y. Otsuka

    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)   出版者・発行元:COPERNICUS GESELLSCHAFT MBH  

    The response of the ionospheric F-region in the South American sector during the super geomagnetic storms on 29 and 30 October 2003 is studied in the present investigation.
    In this paper, we present ionospheric sounding observations during the period 29-31 October 2003 obtained at Palmas (a near equatorial location) and Sao Jose dos Campos (a location under the southern crest of the equatorial ionospheric anomaly), Brazil, along with observations during the period 27-31 October 2003 from a chain of GPS stations covering the South American sector from Imperatriz, Brazil, to Rio Grande, Argentina. Also, complementary observations that include sequences of all-sky images of the OI 777.4 and 630.0 nm emissions observed at El Leoncito, Argentina, on the nights of 28-29 (geomagnetically quiet night) and 29-30 (geomagnetically disturbed night) October 2003, and ion densities observed in the South American sector by the DMSP F13, F14 and F15 satellites orbiting at about 800 km on 29 and 30 October 2003 are presented. In addition, global TEC maps derived from GPS observations collected from the global GPS network of International GPS Service (IGS) are presented, showing widespread and drastic TEC changes during the different phases of the geomagnetic disturbances. The observations indicate that the equatorial ionospheric irregularities or plasma bubbles extend to the Argentinean station Rawson (geom. Lat. 33.1 degrees S) and map at the magnetic equator at an altitude of about 2500 km.

    DOI: 10.5194/angeo-27-4463-2009

    Web of Science

  340. 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

  341. 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

  342. 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

  343. 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

  344. 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

  345. 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)  

  346. 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)  

  347. 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)  

  348. 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

  349. 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.

  350. 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.

  351. 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)  

  352. 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)  

  353. 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)  

  354. 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)  

  355. 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)  

  356. 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)  

  357. 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)  

  358. 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)  

  359. 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 1

  1. 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

講演・口頭発表等 48

  1. トロムソEISCAT サイトでのGPS シンチレーション観測

    大塚雄一、小川泰信、石井守、久保田実、津川卓也、塩川和夫、大山伸一郎

    第124回 地球電磁気・地球惑星圏学会 

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    開催年月日: 2009年9月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  2. ファブリ・ペロー干渉計観測による熱圏中性大気風速とMUレーダーによるF 領域プラズマドリフトの統計解析

    大塚雄一、塩川和夫、小川忠彦、深尾昌一郎

    第124回 地球電磁気・地球惑星圏学会 

     詳細を見る

    開催年月日: 2009年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  3. VHF Radar Observations of Nighttime F-Region Field-Aligned Irregularities Over Kototabang, Indonesia 国際会議

    Asia Oceania Geosciences Society (AOGS) 

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    開催年月日: 2009年8月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

  4. Relationship between medium-scale traveling ionospheric disturbance and sporadic E layer activities in summer night over Japan 国際会議

    Asia Oceania Geosciences Society 2008 

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    開催年月日: 2008年6月

    記述言語:英語   会議種別:口頭発表(一般)  

  5. VHF Radar Observations of Nighttime F-Region Field-Aligned Irregularities Over Kototabang, Indonesia 国際会議

    Asia Oceania Geosciences Society 2008 

     詳細を見る

    開催年月日: 2008年6月

    記述言語:英語   会議種別:口頭発表(一般)  

  6. VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia 国際会議

    12th International Symposium on Equatorial Aeronomy (ISEA-12) 

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    開催年月日: 2008年5月

    記述言語:英語   会議種別:口頭発表(一般)  

  7. Ionospheric variations observed by GPS-TEC and SuperDARN Hokkaido radar following large earthquakes 国際会議

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

     詳細を見る

    開催年月日: 2007年7月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:日本国  

  8. Radar and Optical Observation of Medium-Scale Traveling Ionospheric Disturbances and Field-Aligned Irregularities in the F Region 国際会議

    IUGG XXIV General Assembly 

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    開催年月日: 2007年7月

    記述言語:英語   会議種別:口頭発表(一般)  

  9. Observations of ionospheric variations following the 13 January 2007 earthquake using GPS and Hokkaido HF radar 国際会議

    SuperDARN Workshop 2007 

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    開催年月日: 2007年6月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:日本国  

  10. Radar and Optical Observation of Medium-Scale Traveling Ionospheric Disturbances and Field-Aligned Irregularities in the F Region 国際会議

    AGU Joint Assembly, Acapulco 

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    開催年月日: 2007年5月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

  11. 2007年1月13日の千島列島東方地震後にGPSと北海道-陸別HFレーダーで 観測された電離圏変動: 1. GPS

    大塚雄一、山矢優、西谷望、小川忠彦

    日本地球惑星科学連合2007年大会 

     詳細を見る

    開催年月日: 2007年5月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  12. F領域沿磁力線不規則構造と中規模伝搬性電離圏擾乱のレーダー・光学同時観測

    大塚 雄一、横山 竜宏、塩川 和夫、小川 忠彦、山本 衛

    日本地球惑星科学連合2007年大会 

     詳細を見る

    開催年月日: 2007年5月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  13. Radio and Optical Observations of Medium-scale Traveling Ionospheric Disturbances with the MU radar and All-Sky Airglow Imagers 国際会議

    the 2007 Taiwan Geosciences Assembly 

     詳細を見る

    開催年月日: 2007年5月

    記述言語:英語   会議種別:口頭発表(一般)  

  14. Radar observations of F-region field-aligned irregularities over Indonesia 国際会議

    International Symposium on Coupling Processes in the Equatorial Atmosphere 

     詳細を見る

    開催年月日: 2007年3月

    記述言語:英語   会議種別:ポスター発表  

    国名:日本国  

  15. GPSを用いたインドネシアにおける電離圏擾乱とドリフト速度の観測

    大塚雄一、 塩川 和夫、小川 忠彦

    CAWSES/IHY worskshop 

     詳細を見る

    開催年月日: 2007年3月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  16. 2007年1月13日の千島列島東方地震後にGPSと北海道-陸別

    中緯度短波レーダー研究会 

     詳細を見る

    開催年月日: 2007年2月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  17. F領域沿磁力線不規則構造と中規模伝搬性電離圏 擾乱のレーダー・光学同時観測

    大塚雄一, 横山竜宏, 塩川和夫, 小川忠彦、齋藤昭則、山本衛

    大気圏シンポジウム 

     詳細を見る

    開催年月日: 2007年2月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  18. Relationship between medium-scale traveling ionospheric disturbance and sporadic E layer activities in summer night over Japan 国際会議

    AGU Chapman Conference on Mid-latitude Ionospheric Dynamics and Disturbances 

     詳細を見る

    開催年月日: 2007年1月

    記述言語:英語   会議種別:口頭発表(一般)  

  19. 赤道域電離圏擾乱と対流圏・MLT変動との関係 2

    「赤道大気上下結合」研究成果取まとめミニワークショップ 

     詳細を見る

    開催年月日: 2006年12月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  20. Relationship between medium-scale traveling ionospheric disturbances and sporadic E layer over Japan 国際会議

    Asia Oceania Geosciences Society 3rd Annual Meeting, Singapore, Singapore 

     詳細を見る

    開催年月日: 2006年11月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

  21. GPS全電子数を用いた赤道域電離圏擾乱の6-8日周期変動

    大塚 雄一、津川 卓也、横山 竜宏、他

    地球電磁気・地球惑星圏学会 

     詳細を見る

    開催年月日: 2006年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  22. 2004年12月26日のスマトラ沖地震後のGPS-TEC変動

    中間圏・熱圏・電離圏 (MTI) 研究集会 

     詳細を見る

    開催年月日: 2006年9月

    記述言語:日本語  

  23. GPS全電子数を用いた赤道域電離圏擾乱の6-8日周期変動

    大塚 雄一、津川 卓也、横山 竜宏、小川 忠彦、齊藤 昭則、西岡 未知

    特定領域研究「赤道大気上下結合」平成18年度公開ワークショップ 

     詳細を見る

    開催年月日: 2006年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  24. 中・低緯度における電離圏擾乱: 中規模伝搬性電離圏擾乱(MSTID)

    中間圏・熱圏・電離圏 (MTI) 研究集会 

     詳細を見る

    開催年月日: 2006年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  25. MTI衛星:サイエンス・電離圏

    中間圏・熱圏・電離圏 (MTI) 研究集会 

     詳細を見る

    開催年月日: 2006年9月

    記述言語:日本語  

  26. MTIP衛星の科学目標: 電離圏

    MTI小型衛星による大気圏・宇宙研観測ワークショップ 

     詳細を見る

    開催年月日: 2006年8月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  27. GPS及びイオノゾンデ観測による中規模伝搬性電離圏擾乱と スポラディックE層との関係の研究

    大塚雄一,谷貴行,津川卓也,小川忠彦,齊藤昭則

    日本地球惑星科学連合2006年大会 

     詳細を見る

    開催年月日: 2006年5月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  28. MTI衛星を用いた電離圏・熱圏のサイエンス

    大塚雄一、MTI衛星検討グループ

    人工衛星からの電離圏・熱圏・中間圏撮像観測に関する研究集会 

     詳細を見る

    開催年月日: 2005年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  29. GPSを使った電離圏観測

    サイエンスワークショップ「太陽・地球・生命圏観測の現状と要素技術」 

     詳細を見る

    開催年月日: 2005年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  30. Optical and radio measurements of equatorial plasma bubbles over Indonesia 国際会議

     詳細を見る

    開催年月日: 2005年10月

    記述言語:英語   会議種別:ポスター発表  

  31. GPS detection of total electron content variations over Indonesia and Thailand following the 26 December 2004 earthquake 国際会議

     詳細を見る

    開催年月日: 2005年9月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    国名:日本国  

  32. 信楽のファブリ・ペロー干渉計で観測された熱圏中性大気風速の統計解析

    大塚雄一、塩川和夫、小川忠彦

    地球電磁気・地球惑星圏学会 

     詳細を見る

    開催年月日: 2005年9月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  33. GPSで観測された2004年12月26日のスマトラ島西方沖地震後の電離圏変動

    大塚雄一、 小竹論季、 津川卓也、塩川和夫、小川忠彦、斎藤 享、川村眞文、丸山 隆、Effendy、N. Hemmakorn、T. Komolmis

    平成17年度「赤道大気上下結合」公開ワークショップ 

     詳細を見る

    開催年月日: 2005年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  34. GPSで観測された2004年12月26日のスマトラ島西方沖地震後の電離圏全電子数変動

    大塚雄一、 小竹論季、 津川卓也、塩川和夫、小川忠彦、斎藤 享、川村眞文、丸山 隆、Effendy、N. Hemmakorn、T. Komolmis

    CAWSES workshop (第6回宇宙天気/気候シンポジウム) 

     詳細を見る

    開催年月日: 2005年9月

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    国名:日本国  

  35. Measurements of ionospheric irregularity drift using spaced GPS receivers in Indonesia 国際会議

    11th International Symposium on Equatorial Aeronomy and CAWSES Mini-Workshop 

     詳細を見る

    開催年月日: 2005年5月

    記述言語:英語   会議種別:口頭発表(一般)  

  36. 2004年12月26日のスマトラ島西方沖地震後の電離圏全電子数変動

    大塚雄一、津川卓也、小竹論季、塩川和夫、小川忠彦

    地球惑星科学関連学会合同大会 

     詳細を見る

    開催年月日: 2005年5月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  37. GPS detection of total electron content variations following the 26 December 2004 earthquake 国際会議

    11th International Symposium on Equatorial Aeronomy and CAWSES Mini-Workshop 

     詳細を見る

    開催年月日: 2005年5月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

  38. 2004年12月26日のスマトラ島西方沖地震後の電離圏全電子数変動

    大塚雄一、津川卓也、小竹論季、塩川和夫、小川忠彦

    全国共同利用化に向けた第9回生存圏シンポジウム「赤道大気レーダーによる電離圏研究とその広がり」 

     詳細を見る

    開催年月日: 2005年3月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  39. Total electron content variations during geomagnetic storms: From the dense GPS Network in Japan 国際会議

    Chapman Conference on Corotating Solar Wind Streams and Recurrent Geomagnetic Activity 

     詳細を見る

    開催年月日: 2005年2月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

  40. 中規模伝搬性電離圏擾乱のレーダー・光学観測

    大塚雄一、塩川和夫、小川忠彦、齊藤昭則、大島浩嗣、深尾昌一郎

    ISAS第19回大気圏シンポジウム 

     詳細を見る

    開催年月日: 2005年2月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  41. 衛星大気光観測・電離圏現象

    大塚雄一、塩川和夫、小川忠彦、斉藤昭則

    中間圏・熱圏・電離圏研究会 

     詳細を見る

    開催年月日: 2004年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  42. GPSによる赤道域電離圏イレギュラリティのドリフト速度観測

    大塚雄一、服部 誠、伊藤義訓、塩川和夫、小川忠彦

    中間圏・熱圏・電離圏研究会 

     詳細を見る

    開催年月日: 2004年11月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  43. 第一回CPEAキャンペーン期間中におけるプラズマバブルの観測 - 速報-

    大塚雄一、服部 誠、塩川和夫、小川忠彦、深尾昌一郎、山本 衛、多山哲郎、丸山 隆、佐川永一、斎藤 享

    第116回SGEPSS 

     詳細を見る

    開催年月日: 2004年9月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  44. GPS三点観測による赤道域F領域イレギュラリティのドリフト速度の測定

    第116回SGEPSS 

     詳細を見る

    開催年月日: 2004年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  45. Goemanetic conjugate observations of medium-scale traveling ionospheric disturbances with all-sky imagers 国際会議

    1st Asia Oceania Geosciences Society (AOGS) 

     詳細を見る

    開催年月日: 2004年7月

    記述言語:英語   会議種別:ポスター発表  

  46. 大気光イメージャーによる電離圏の磁気共役点観測 国際会議

     詳細を見る

    開催年月日: 2004年5月

    記述言語:英語   会議種別:ポスター発表  

    国名:日本国  

  47. 観測点を増やした場合におけるSBASに対する効果

    大塚雄一、小川忠彦、星野尾一明、松永圭左、斎藤昭則

    地球惑星科学関連学会合同大会 

     詳細を見る

    開催年月日: 2004年5月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

  48. 大気光イメージャーによる中規模伝搬性電離圏擾乱の磁気共役点観測

    大塚雄一、塩川和夫、小川忠彦、斎藤昭則、大島浩嗣

    地球惑星科学関連学会合同大会 

     詳細を見る

    開催年月日: 2004年5月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

▼全件表示

共同研究・競争的資金等の研究課題 2

  1. プラズマバブル測定用全天カメラの現地調整

    2005年 - 2006年3月

      詳細を見る

    資金種別:競争的資金

    静止衛星型衛星航法補強システムの2周波対応に関する研究における電離圏シンチレーションの影響を調べるため、全天大気光カメラを与那国島に設置し、その原因であるプラズマバブルの発生特性を明らかにする。

  2. プラズマバブル測定用全天カメラの開発

    2004年10月 - 2005年3月

      詳細を見る

    資金種別:競争的資金

    静止衛星型衛星航法補強システムの2周波対応に関する研究における電離圏シンチレーションの影響を調べるため、全天大気光カメラを開発し、その原因であるプラズマバブルの発生特性を明らかにする。

科研費 32

  1. GPSシンチレーション観測による極域電離圏イレギュラリティの研究

    2011年4月 - 2014年3月

    科学研究費補助金  基盤研究(B)

    大塚雄一

      詳細を見る

    担当区分:研究代表者 

  2. 電離圏・熱圏の春・秋非対称性

    2011年4月 - 2014年3月

    科学研究費補助金  基盤研究(C)

    大塚雄一

      詳細を見る

    担当区分:研究代表者 

  3. 低緯度電離圏不規則構造のレーダー・イメージング観測

    2008年4月 - 2011年3月

    科学研究費補助金  若手研究(A)

    大塚 雄一

      詳細を見る

    担当区分:研究代表者 

  4. GPS受信機網を用いた地震起源の電離圏変動に関する研究

    2006年4月 - 2008年3月

    科学研究費補助金 

      詳細を見る

    担当区分:研究代表者 

  5. レーダー観測網・複数衛星・モデル計算を総合した赤道域電離圏変動特性の国際共同研究

    研究課題/研究課題番号:20H00197  2020年4月 - 2025年3月

    山本 衛

      詳細を見る

    担当区分:研究分担者 

    強い不安定現象である赤道プラズマバブル(Equatorial PlasmaBubble; EPB)の国際共同研究を実施する。EPB活動度が日々変動する原因として有力なLarge-Scale Wave Structure (LSWS)仮説がある。その検証を目指して、赤道大気レーダーと観測網SEALIONによる連続観測を継続、GNSS (衛星測位)受信機を増強する。地表から電離圏までの全大気計算モデルGAIA、EPBの生成・成長を正確に模擬する非線形計算モデルを活用した研究を推進する。地上観測、衛星観測、シミュレーションを駆使した総合研究に取り組むもので、世界をリードする成果が期待される。

  6. 地上多点ネットワーク観測による内部磁気圏の粒子・波動の変動メカニズムの研究

    研究課題/研究課題番号:16H06286  2016年4月 - 2021年3月

    塩川 和夫

      詳細を見る

    担当区分:研究分担者 

    本事業で各観測点に設置されたVLFアンテナ、誘導磁力計、高感度全天カメラ、リオメータ、EMCCDカメラや、平成28年12月に打ち上げられたあらせ衛星、本事業で開発されているモデリングなどを通じ、平成30年度には58件の査読付き論文を出版することができた。代表的な成果として以下のような結果が挙げられる。
    ・オーロラ帯から低緯度に分離してくるSARアークという赤いオーロラを見出し、カナダのサブオーロラ帯での長期観測データから、その統計的な特徴を明らかにした。このSARアークは、日本で見られる低緯度オーロラの原因の一つと考えられる。
    ・極小期の太陽の太陽風に特徴的な構造であるCIRに到来に伴い、180度以上の広い経度で同時にPc1地磁気脈動が発生している例が報告された。この例は、極小期で放射線帯電子の消失に寄与するイオンサイクロトロン波動がグローバルに発生しうることを示す重要な成果である。
    ・このCIRの到来で発生した磁気嵐の主相で、放射線帯電子が急激に減少していることがあらせ衛星で観測された。同時に観測された地上のデータから、Pc1地磁気脈動=イオンサイクロトロン波動がこの消失に寄与していることが示唆されている。
    ・あらせ衛星で観測された磁気圏ELF/VLF波動の明滅と、地上のEMCCDカメラで観測された脈動オーロラの一種であるフラッシュオーロラの明滅が一対一で対応している例を見出し、このELF/VLF波動がフラッシュオーロラを生成させていることを明らかにした。
    ・フィンランド、アイスランド、カナダ、ロシア、アラスカ、日本などの既存の観測点の自動定常観測を維持・継続するとともに、ロシアのZhigansk観測点にカメラを設置し、自動定常観測を開始した。これにより、カナダのNain観測点以外のすべての予定していた観測点において、自動定常観測を開始することができた。また、Nain観測点もVLFアンテナ、カメラ、リオメータ、誘導磁力計の設置を終了し、キャンペーンベースで稼働させることができている。
    ・これらの観測で得られるデータをERGサイエンスセンターとIUGONETによるデータベースを利用してデータベース化して公開し、国内・海外との共同研究を促進することができた。
    ・平成29年3月に定常観測を開始した日本のERG(あらせ)衛星の軌道に合わせて、平成30年度の春・秋にもキャンペーン観測を行った。また、米国のVan Alllen Probe衛星、THEMIS衛星などの内部磁気圏衛星との同時観測データの解析を進めることができた。
    ・波動と粒子の相互作用を局所的およびグローバルに評価するモデリングの開発を継続し、これらの観測と比較することで、モデルの改良と粒子加速・消失の定量評価を行った。
    ・カナダのNain観測点には、フィールド機器は設置できたが、電源が無いためにパソコンなどの記録計を設置して観測を開始することができていない。今後、記録計を設置するとともに、電源が得られない場合は発電機を活用してあらせ上空通過時などに観測を行ってデータを取得していく。
    ・本研究では8か所の観測点・5種類の機器から大量のデータを得ている。これらの観測データはすべて大容量ストレージに保管され、世界的に広く使われているCDFフォーマットに変換されて、ネットワークを介して世界の研究者に公開されている。昨年度に引き続き、新しく得られてくるデータも世界の研究者に公開し、データ利用の促進と成果の創出をはかっていく。
    ・本事業ではホームページ(http://www.isee.nagoya-u.ac.jp/dimr/PWING/)を立ち上げてデータの説明や進捗状況、データへのリンク先などを公開している。このホームページを引き続き運用し、情報発信をはかっていく。さらに、関連研究の国際ワークショップや国際シンポジウムを開催して、成果の創出をはかっていく。
    ・本研究の成果は、科学論文として発表していくだけでなく、さまざまな形で社会へ発信していくことが重要である。このために、出前授業や、大学院生・若手研究者向けの国際スクール、重要な成果のプレスリリースなどを実施していく。

  7. 人工衛星電波を用いた電離圏シンチレーション観測のカスプ・極冠域への展開

    研究課題/研究課題番号:16H05736  2016年4月 - 2019年3月

    大塚 雄一

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    担当区分:研究代表者 

    配分額:17290000円 ( 直接経費:13300000円 、 間接経費:3990000円 )

    低軌道衛星から送信される電波の受信装置、及びGPSなど汎地球測位衛星システム(GNSS)の電波を受信する受信機を極冠域及びオーロラ帯に設置し、電離圏構造とイレギュラリティの観測を実施した。イレギュラリティによって生じる電波の揺らぎであるシンチレーションの発生特性を明らかにし、イレギュラリティの移動速度を導出した。また、磁気嵐中に発生する電離圏イレギュラリティの発生機構について新しい発見があった。
    電離圏にはプラズマが存在しているため、電離圏内を伝搬する電波は、プラズマとの相互作用により、真空中での伝搬とは異なった速度をもつ。このため、GPSなどの衛星測位にとって、電離圏は測位誤差の要因となる。また、電離圏中にプラズマ密度の疎密構造が存在すると、電離圏を透過する電波の位相や振幅が変動することがある。この現象はシンチレーションと呼ばれており、激しいシンチレーションが起こると、衛星放送・通信が途絶えたり、GPSなどの衛星測位に対して誤差をもたらすことがある。本研究では、これら電離圏擾乱の特性を調べた。

  8. 地球電磁気圏擾乱現象の発生機構の解明と予測

    研究課題/研究課題番号:15H05815  2015年6月 - 2020年3月

    新学術領域研究(研究領域提案型)

    三好 由純

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    担当区分:研究分担者 

    本計画班では、人類の活動に特に大きな影響を及ぼす宇宙天気現象のうち、宇宙放射線、電離圏変動、地磁気誘導電流(GIC)の3つに焦点をあてて研究活動を進めてきた。宇宙放射線については、プラズマ波動による放射線帯粒子加速および消失の実証的な観測に成功した。電離圏変動については、1-2日先までの電離圏変動予測を可能とするシステムを構築した。GICについては、物理シミュレーションを構築し、日本の送電線網を流れるGICの計算を可能にするとともに、高い精度での再現に成功した。
    本計画研究では、人類の社会活動、宇宙活動に大きな影響を与える宇宙天気現象のうち、宇宙放射線、電離圏変動、地磁気誘導電流に焦点をあてて研究を進めてきた。新しい人工衛星の観測データや、本計画で新たに設置した地上観測点データ、また本計画で独自に開発したシミュレーション群を用いた研究によって、各現象の物理素過程の理解を飛躍的に進めるとともに、太陽、太陽風の変動に応じて、各現象の変動予測を可能とするモデルを構築し、実際の現象の予測を可能にした。

  9. 人工衛星-地上ネットワーク観測に基づく内部磁気圏の粒子変動メカニズムの研究

    研究課題/研究課題番号:25247080  2013年4月 - 2017年3月

    塩川 和夫

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    担当区分:研究分担者 

    ・ロシアのZhigansk観測点において、誘導磁力計による定常観測を平成28年9月14日より開始し、良好なデータが取得できていることを確認した。ロシアのZhigansk観測点を管轄するヤクーツクのIKFIA研究所に、平成28年9月末にVLFアンテナ、高感度全天カメラを送付した(平成27年度の本計画の繰り越し分による実施)。また、関連機器による定常観測が行われている既存の観測点であるアサバスカ、トロムソ、マガダン、パラツンカ、レゾリュート、国内の母子里、陸別、信楽、鹿児島、佐多などの自動観測を維持・継続した。
    ・アサバスカ、マガダン、パラツンカの誘導磁力計による5年間の同時観測データを統計的に解析して、Pc1帯地磁気脈動の振幅変調の観測点ごとに違いの季節・太陽活動度・地方時・地磁気活動度などへの依存性を明らかにした。この結果から、この波動の振幅変調が磁気圏ではなく電離圏の伝搬中にうなりによって発生していることを示唆した。また、アサバスカで1年間に観測されたVLF/ELF帯波動の統計解析を行い、この波動の季節・地方時・地磁気活動度などへの依存性を明らかにした。これらの波動は、人工衛星に悪影響を及ぼす放射線帯粒子の加速や消失を引き起こしていることがわかっており、今回の結果は、この加速・消失過程の時間・空間変化に示唆を与えるものである。
    ・なお、本計画は、研究代表者が平成28年度から別の特別推進研究の代表者になったために、平成28年度途中で廃止になった。本計画で予定されていたカナダ中部のアサバスカ、カナダの東海岸、及び、ロシアのZhigansk観測点における光学・電磁場計測は、この特別推進研究によって引き続きおこなわれることになった。
    28年度が最終年度であるため、記入しない。
    28年度が最終年度であるため、記入しない。

  10. 赤道大気レーダーと広域観測網による赤道スプレッドF現象と電離圏構造の関連の解明

    研究課題/研究課題番号:25302007  2013年4月 - 2017年3月

    山本 衛

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    担当区分:研究分担者 

    電離圏の強い不安定現象である赤道スプレッドF現象(EquatorialSpread-F;-ESF)と電離圏構造の解明を目指した。具体的には、(1)赤道大気レーダーによる長期連続観測からESFの統計的性質を明らかにし、(2)東南アジアに展開された観測網からESFの時空間変動と背景の電離圏・熱圏大気の関連を明らかにし、(3)衛星ビーコン観測網の更なる拡張と国際宇宙ステーションからの大気光観測の活用を目指した。研究成果を査読付き論文26編に結実させることができた。

  11. 異なる地域の対流圏活動が起こす中間圏変動の地上と宇宙からの同時観測

    研究課題/研究課題番号:24403008  2012年4月 - 2016年3月

    齊藤 昭則

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    担当区分:研究分担者 

    本研究は、地上大気光観測イメージャと国際宇宙ステーションからのISS-IMAPミッションとの同時観測を行う事により、異なる地域の対流圏活動が中間圏やさらにその上の熱圏に与える影響を観測的に解明する事を目的とした。また、地上観測と宇宙からの観測との同時観測により、宇宙からの観測データの校正をする事も目的とした。地上観測としては東北大学ハワイ・ハレアカラ観測所に大気光観測イメージャを設置しそのデータを主に利用した。本研究によって、中間圏における大気光波状構造の衛星と地上の同時観測に成功し、対流圏と超高層大気を結びつける役割を果たしている大気重力波の特性が明らかにされた。

  12. ロケット・地上連携観測による中緯度電離圏波動の生成機構の解明

    研究課題/研究課題番号:24340120  2012年4月 - 2015年3月

    山本 衛

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    担当区分:研究分担者 

    本研究はロケット観測と地上観測の連携によって中規模伝搬性電離圏擾乱(MSTID)の発生機構を解明することを目的として実施された。2013年7月20日にJAXA内之浦宇宙空間観測所から観測ロケットS-520-27号機、S-310-42号機を打上げ、航空機観測、地上観測を同時に実施した。MSTIDに伴う電子密度と電場の大きな変動が観測され、同時にスポラディックE層が存在した。中性風速の振舞いを含めて、事前に予想されたモデルにほぼ近い状況の実証に成功した。世界初の試みとして、ほぼ満月の真夜中の条件でS-520-27号機からリチウム蒸気を噴射し、航空機と地上の両方から共鳴散乱光の撮像に成功した。

  13. 電離圏・熱圏の春・秋非対称性

    研究課題/研究課題番号:23540523  2011年4月 - 2015年3月

    大塚 雄一

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    担当区分:研究代表者 

    配分額:4940000円 ( 直接経費:3800000円 、 間接経費:1140000円 )

    長期間わたって中間圏及び電離圏の観測を行っている、大型大気レーダーであるMUレーダーによって観測された中間圏エコーのデータを解析し、乱流拡散係数を求め、乱流拡散係数が春よりも 秋に大きいことを明らかにした。全球モデルによる結果を考慮すると、この乱流拡散係数の春・秋非対称性は、電離圏電子密度の春・秋非対称性の原因となっていると言える。また、タイのチェンマイに設置されたファブリ・ペロー干渉計で観測された熱圏風のデータを解析し、南北方向の熱圏風の春・秋非対称性がプラズマバブル発生頻度の春・秋非対称性の主な原因と考えられることを示した。

  14. GPSシンチレーション観測による極域電離圏イレギュラリティの研究

    研究課題/研究課題番号:23403010  2011年4月 - 2015年3月

    大塚 雄一

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    担当区分:研究代表者 

    配分額:20020000円 ( 直接経費:15400000円 、 間接経費:4620000円 )

    GNSS受信機3台をノルウェー・トロムソのEISCATレーダーサイトに設置し、GNSS衛星が送信する2周波の電波の位相と信号強度を記録するシステムを構築した。これにより、電離圏擾乱によって生じる電波の変動(シンチレーション)を観測し、光学観測で捉えられたオーロラとの比較を行った。また、欧州における800点以上のGNSS受信機から得られたデータを用い て、全電子数を算出し、伝搬性をもつ電離圏擾乱の統計的性質を明らかにした。

  15. インド・東南アジア・太平洋の広域観測による赤道スプレッド F 現象の日々変動の解明

    研究課題/研究課題番号:22403011  2010年 - 2012年

    山本 衛

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    担当区分:研究分担者 

    赤道スプレッドF現象(Equatorial Spread-F、ESF と略記、プラズマバブルとも呼ばれる)は電離圏の最も強い擾乱の一つであり、近年の高度な衛星利用、特に GPS 測位に悪影響を与え得る。本研究では、未だ謎の深い ESF の日々変動を中心として、アジアから太平洋にわたる広域に各種のレーダー・大気光観測装置・衛星ビーコン受信機等による観測網を構築して国際共同研究を展開した。ESF の日々変動に関して、午後の時間帯に発生する波長数百 km の大規模波動構造(Large-Scale Wave Structure; LSWS)が日没と共に振幅を増大し、 ESF 発生に結びつく様子を見出した。また太陽活動度が低い時期には、夜半過ぎに ESF 類似の現象が発生することを明らかにした。

  16. GPS受信機網を利用した電離圏擾乱のスケール間結合と衛星測位への影響に関する研究

    研究課題/研究課題番号:22740326  2010年 - 2011年

    津川 卓也

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    担当区分:その他 

    国内外のGPS受信機網データから、電離圏全電子数や電離圏擾乱指数、GPSロック損失率等の2次元マップを作成し、データベース化した。これらのデータを用い、伝搬性電離圏擾乱やプラズマバブル等の電離圏擾乱の統計的性質を明らかにすると共に、衛星測位への影響について調べた。日本上空については、全電子数リアルタイム2次元観測を開始し、東北地方太平洋沖地震後に津波波源から波紋状に拡がる電離圏変動の詳細を世界で始めて捉えた。

  17. ディジタル受信機を用いたパッシブレーダーによるプラズマバブル広域監視法の研究開発

    研究課題/研究課題番号:21740357  2009年 - 2011年

    齋藤 享

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    担当区分:その他 

    パッシブレーダー技術を用いて短波放送波の伝播距離を測定する装置を、ディジタルソフトウェア受信機を利用して開発した。開発した装置を用いて豪州から赤道を越えて日本へ伝播する短波放送波の伝播遅延から伝播距離を測定し、同時に方向探査装置によりその到来方向を測定する実験を行った。伝播距離と到来方向の同時測定により、プラズマバブルの位置推定精度を高め、その発生を広域で効率的に監視することができる見通しを得た。

  18. 高感度分光多点観測による超高層大気変動の研究

    研究課題/研究課題番号:20244080  2008年4月 - 2013年3月

    塩川 和夫

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    担当区分:研究分担者 

    ロシア、カナダ、日本、ノルウェー、インドネシア、タイ、オーストラリアなどにおけるファブリ・ペロー干渉計5台と高感度全天カメラ10台以上を用いた夜間大気光の高感度分光多点観測から、高度80-300kmの地球の超高層大気の擾乱に関するさまざまな研究成果が得られた。代表的な成果の例として、夜間に発生する中規模伝搬性電離圏擾乱(MSTID)のオーロラ帯付近での振る舞いの解明や、80-90km高度の中間圏の大気重力波のダクト伝搬の可視化、台風から発生した大気重力波が中間圏界面付近まで伝搬している様子、赤道域プラズマバブル現象の東向き伝搬と中性大気の風の関係(F層ダイナモ過程を示唆)、などが挙げられる。

  19. 低緯度電離圏不規則構造のレーダー・イメージング観測

    研究課題/研究課題番号:20684021  2008年 - 2010年

    大塚 雄一

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    担当区分:研究代表者 

    配分額:22620000円 ( 直接経費:17400000円 、 間接経費:5220000円 )

    インドネシアにおいてVHFレーダーを用いて電離圏E及びF領域の沿磁力線不規則構造(Field-Aligned Irregularity;FAI)の連続観測を行い、FAI発生頻度の地方時、季節及び太陽活動度依存性や伝搬特性、ドリフト速度などの統計的性質を明らかにした。特に、これまで研究されてこなかった、低太陽活動期に発生する真夜中過ぎFAIの特性を明らかにし、その生成機構がプラズマバブルおよび中規模伝搬性電離圏優乱に起因し得ることを示した。

  20. 大気圏-電離圏統合モデルによる超高層大気の変動機構の解明と数値予測システムの構築

    研究課題/研究課題番号:20200047  2008年 - 2010年

    新学術領域研究(研究課題提案型)

    陣 英克

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    担当区分:連携研究者 

    本研究では、大気圏モデルと電離圏モデルを結合し、世界に先駆けて対流圏から電離圏までの全地球大気領域を扱う数値モデルの開発に成功した。この大気圏-電離圏統合モデルを用いて、近年注目されている気象の影響による超高層大気(熱圏・電離圏)の経度依存性や日々変動との関連を明らかにした。さらに、気象再解析データを取り込んだ現実に近い超高層大気モデリングを実現し、気象の影響を含む超高層大気の数値予測に向けて大きく進展した。

  21. 大型短波レーダーによる中・高緯度電離圏プラズマー超高層大気相互作用の研究

    研究課題/研究課題番号:19340141  2007年 - 2010年

    西谷 望

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    担当区分:連携研究者 

    本研究では、2006年11月に稼働を開始した北海道-陸別HFレーダーを主に活用し、北海道北方からオホーツク海、極東シベリア領域にわたる電場擾乱等の電離圏プラズマ関連現象と伝搬性電離圏擾乱等の超高層大気関連現象の間の相互作用の解明に焦点を置いて研究を進め、サブオーロラ帯電場擾乱の発生条件や伝搬性電離圏擾乱による電離圏プラズマ構造運動のメカニズム、および巨大地震後に超高層大気変動により引き起こされる電離圏プラズマ変動の特性等を明らかにした。

  22. シベリア域から日本におけるジオスペース環境変動の衛星-地上共同観測

    研究課題/研究課題番号:18403011  2006年 - 2009年

    塩川 和夫

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    担当区分:研究分担者 

    ロシア極東域のパラツンカ観測点、マガダン観測点に高感度全天カメラ・誘導磁力計を設置、日本に設置した高感度全天カメラ、誘導磁力計、北海道のSuperDARNレーダーを組み合わせて、極東シベリア域から日本にかけての超高層大気の観測網を構築した。これらのデータと、上空を飛翔する人工衛星データを組み合わせて、低緯度オーロラを引き起こす特殊な電子降り込みの特性や、サブオーロラ帯から中緯度における電離圏の擾乱の特性を明らかにした。

  23. GPS受信機網を用いた地震起源の電離圏変動に関する研究

    研究課題/研究課題番号:18654083  2006年 - 2007年

    萌芽研究

    大塚 雄一

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    担当区分:研究代表者 

    配分額:2300000円 ( 直接経費:2300000円 )

    国内外のGPS観測データを収集し、電離圏における全電子数(Total Electron Content;TEC)を算出し、そのデータベースを作成することにより、以下の結果を得た。
    1.2000年1月から2007年10月までに日本で起きたマグニチュード6.0以上の地震(20例)について、地震発生後のTEC変動を調べた。このうち、2004年9月5日の紀伊半島沖地震、2007年1月13日の千島列島東方沖地震、2007年3月25日の能登半島地震、2007年7月16日の新潟県中越沖地震の4例において、地震発生から十数分後に震央の位置から遠ざかる方向に伝搬するTEC変動が観測された。さらに、そのうちの3例において、赤道向きに伝搬するTEC変動の振幅が他の方向に伝搬する場合よりも大きいことが明らかになった。この結果は、地震によるTEC変動は、地震に伴って発生した音波が原因であり、音波による中性大気の振動によって電離圏プラズマは磁力線平行方向にのみ動かされるため、このような震央に対する非等方的なTEC変動が起こる、と考えられる。本研究の結果は、地表付近の大気波動が超高層大気に与える影響は小さくないことを表しており、大気の上下結合を解明する重要性を示している。
    2.米国に設置されている1400台以上のGPS受信機を用いて、米国上空における電離圏全電子数の2次元マップを作成した。これまでに、中規模伝搬性電離圏擾乱や電離圏トラフの広域水平二次元構造が明らかになり、新たな観測結果が得られている。さらに、従来知られていない電離圏現象(例えば、線状に1,000km以上細長く伸びた領域でTECが増大・減少し、数10分で消滅する現象)も観測されており、電離圏の2次元観測の有効性が示された。

  24. 地球熱圏大気プラズマのスーパーローテーション-日本・インド・台湾共同観測

    研究課題/研究課題番号:18340147  2006年 - 2007年

    渡部 重十

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    担当区分:研究分担者 

    スペースシャトル,宇宙ステーション,人工衛星が飛翔する高度100km以上の熱圏には,中性大気中に0.01%ほどのプラズマが混在している.プラズマは磁力線に束縛された運動をするため,中性大気とプラズマ間には無視できない運動量輸送が存在する.最近の衛星観測やモデリングは,中性大気の運動がプラズマの運動に強く依存していること,電磁場を介したプラズマの運動が中性大気の運動をコントロールしていること,熱圏中性大気の東向きスーパーローテーションがプラズマとの相互作用に起因している可能性があること,を明らかにした.しかし,中性大気とプラズマの運動を熱圏上部で同時に測定した例はない.
    平成19年9月2日19:25に宇宙航空研究開発機構/内之浦宇宙空間観測所からS520ロケットを打ち上げた.このロケットにリチウムガス放出装置とプラズマ・電磁場観測装置が搭載された.〜1000Kのリチウムガスを230km,190km,140km高度でロケットから放出した.リチウムガスによる太陽光の共鳴散乱を地上の多地点から観測し,上部熱圏風の高度分布を測定することに世界で初めて成功した.リチウムガスの拡散から大気温度と密度の高度分布を得ることにも成功した.中性大気の物理パラメータとロケットに搭載したプラズマ測定と比較することにより,中性大気とプラズマ間の相互作用過程を解明することが可能となる.本研究により,ロケットからのガス放出技術,高感度CCDカメラを用いた地上観測技術,画像解析による大気パラメータの導出技術,を確立することもできた.

  25. 中緯度電離圏における力学的・電磁力学的上下結合過程の研究

    研究課題/研究課題番号:18340151  2006年 - 2007年

    山本 衛

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    担当区分:研究分担者 

    電離圏では電離圏プラズマと背景の(電気的)中性大気が密接に相互作用している。プラズマ密度に空間不均一があると、分極電界が発生し磁力線に沿って伝播することから、遠く離れた電離圏の間に電磁力学的な相互作用が生じる。本研究では、4つの研究課題について以下の成果を得た。
    課題1:ブレーンストーミングによる大気圏・電離圏相互作用研究の新展開
    平成18年度に中緯度電離圏の相互作用に関する国際ワータショップを開催し、現在までの到達点と将来の方向について議論した。この議論から次期のロケット観測計画をとりまとめてJAXAに提案している。
    課題2:F領域E領域FAIカップリングの統合観測実験
    平成19年度にMUレーダーによる電離圏F領域FAI観測と山形県酒田市からの小型レーダーによるE領域FAI観測、さらに大気光イメージャを組合せた、同一磁力線上にある電離圏相互作用の統合観測FERIX-2を実施した。F領域FAIが20-30kmの小領域から構成され北西-南東に延びる波面に沿って北西方向に移動すること、E領域FAIは同一磁力線上のF領域FAIの空白域に現れることなどを明らかにした。
    課題3:MUレーダーイメージング観測によるFAI微細構造の観測
    MUレーダーを用いたFAIエコーのイメージング観測法の開発を進めた。E領域FAI観測とGPS-TECに基づく電離圏相互作用に関する論文、F領域FAIエコーの微細構造に関する論文などを公表した。本課題の成果に基づいて、FERIX-2観測においてイメージング観測を全面的に採用した。
    課題4:衛星・ロケットによる電離圏ビーコン観測実験
    平成19年度にJAXA宇宙科学研究本部が実施した観測ロケット実験に参加して、ロケット-地上間のビーコン観測を実施した。またビーコン観測用ディジタル受信機を独自に開発し、観測ロケット実験に利用した。

  26. 太陽フレアによる極端紫外線(EUV)の電離圏応答に関する観測的研究

    研究課題/研究課題番号:17540422  2005年 - 2007年

    増田 智, 佐藤 淳

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    担当区分:研究分担者 

    本研究では、太陽活動と電離圏の対応を観測的に明らかにしようとした。これらは、(1)太陽フレアX線データの整備と、EUV観測データの取得(2)太陽フレアの観測的性質に関する研究(3)EUVデータ解析手法の確立とデータ解析(4)(1)とGPSデータを用いた、フレアによる大気中の電子数の増加に関する観測的研究に大きくわけられる。(1)は「ようこう」の観測データを主として作成し、世界の太陽研究者に初めて画像と時間変動を含めた太陽フレアX線データを約10年分提供することを可能にした。(2)については(1)を使って、太陽フレアを統計的に解析し、ほとんど観測例がない太陽X線放射源の密度の高さ依存性を数百km単位で明らかにした。(3)EUV観測データは時間と波長帯が限られるので、不足分を補うため数値シミュレーションを用いて時間的に連続な擬似データ作成を試み、数倍程度の範囲内で観測データと一致させることを可能にした。また、EUVデータ、F10.7、TSI(Total Solar Irradiance)、X線データの相互の関係を調べ、F10.7はEUVとは相関が良いが、TSIの代用とするには問題があるとの結果を得た。(4)太陽フレア発生時での太陽天頂角、フレア強度、全電子数の増加を統計的に調べ、EUV放射強度と全電子数の増加が一次の比例関係であることを明らかにした。また、GPSデータから得られる全電子数の増加はEUV波長域の変化に良く対応し、GPSデータに影響を及ぼす層はF層であるとの確信を得た。さらに、夏半球と冬半球で電離圏電子数の変動を調べ、フレアによるエネルギー注入以外に、背景となる大気の状態が影響を与えることを明らかにした。

  27. カナダ北極域におけるオーロラ・超高層大気の高感度光学観測

    研究課題/研究課題番号:16403007  2004年 - 2006年

    小川 忠彦

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    担当区分:研究分担者 

    本研究により、極冠域のResolute Bay観測点(磁気緯度83度)に、平成17年1月に高感度全天カメラを設置し、自動観測を開始した。さらに平成17年9月には、高感度全天カメラ、掃天分光フォトメータ、誘導型磁力計をサブオーロラ帯のAthabasca観測点(磁気緯度62度)に設置し、こちらも自動観測を開始した。平成19年現在、どちらも順調に観測を継続している。また、平成18年6月から平成19年4月に、高感度全天カメラを米国・ニューヨーク州Ithacaに設置し、自動観測を行った。本研究の結果として、Resolute Bayで得られた極冠域パッチ現象のデータから、パッチの動きが惑星間空間磁場の変動と非常に良い相関があることを見いだした。この結果は、極冠域のプラズマ対流を可視化し、太陽風の変動に対して磁気圏のプラズマ対流がどのように応答するかを調べるための新たなツールを与えている。このパッチの動きと、Super DARNレーダーで得られるプラズマ対流の動きの比較も行われている。また、Athabascaで得られたオーロラ、地磁気データから、オーロラ帯から赤道側に離れた孤立オーロラとPc1地磁気脈動が1対1対応していることを初めて見いだし、地球の内部磁気圏において、波動と粒子の相互作用が従来考えられていたよりもはるかに空間的に狭い領域で発生していることを示した。
    これら3点の観測から得られるデータはすべてデータベース化され、プロットがホームページで公開されている。また、これらの観測と共同研究が期待されるTHEMIS衛星は、平成19年2月17日に米国から打ち上げられ、平成19年度後半には、カナダの観測点上空でオーロラサブストームに関する共同観測を行うことになっている。

  28. ロケット・レーダー同時観測による電離圏E領域イレギュラリティの生成機構の研究

    研究課題/研究課題番号:14340145  2002年 - 2003年

    深尾 昌一郎

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    担当区分:研究分担者 

    文部科学省宇宙科学研究所鹿児島宇宙空間観測所(KSC)からS-310観測ロケット2機を打上げ、地上観測と組合せて電離圏E領域の観測キャンペーンSEEK-2(Sporadic-E Experiment over Kyushu)を実施した。SEEK-2は、中緯度電離圏E領域の中性大気風速の強いシア(速度の高度変化)や強い分極電界の発生といった現象を統一的に理解し、電離圏の沿磁力線イレギュラリティ(Field-Aligned Irregularity;FAI)の生成機構を明らかすることを目的として計画されたものである。本研究の成果は以下のとおりである。
    1.種子島に2機のレーダーを設置し、高知、高崎(宮崎)、内之浦、種子島にTMA発光雲の写真観測点及びロケットビーコン電波の地上受信点等を設置するなど、SEEK-2観測の準備を進めた。2002年8月3日23時〜24時の期間、種子島設置のレーダーで強いFAIを観測中に、KSCからの観測ロケット2機の連続打上げ(15分間隔)に成功した。ロケット搭載機器は全て順調に動作し、地上観測も成功裡に実施された。
    2.レーダー干渉計観測から、E領域FAIに見られる空間構造が主としてスポラディックE層の水平不均一性によって発生していることが見出された。強い不均一構造によって、レーダー電波が屈折を受ける様子が計算機シミュレーションから明らかになった。
    3.3次元の計算機シミュレーションを開発し、SEEK-2ロケット観測結果等をもとに研究を進めた結果、中性大気風速の強いシア(速度の高度変化)による強いスポラディックE層が現れること、分極電界の効果によって2次的な電子密度のピークが説明されることが明らかになった。更に大気重力波のシミュレーション結果を取り入れることで、大気重力波の効果によってE領域FAIの空間構造が生成される様子が見出された。

  29. 赤道大気エネルギーによる熱圏変動の研究

    研究課題/研究課題番号:13136201  2001年 - 2006年

    小川 忠彦

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    担当区分:研究分担者 

    本研究課題の当初の設定目標は、1)赤道域対流圏に起源を持つ大気波動のエネルギーや運動量が熱圏高度に輸送されて散逸する過程と、2)散逸エネルギーが誘起する熱圏大気の変動と電離圏プラズマの応答過程を研究し、大気活動が世界で最も活発なインドネシア域に特有の赤道大気上下結合を解明することであった。このため、インドネシア域の高度80〜500kmの熱圏・電離圏を探査する独自の装置(光・電波観測装置、VHFレーダー、磁力計)をスマトラ島コトタバンの赤道大気レーダーサイトに設置して連続観測を実施するとともに、赤道レーダーを中心としたリージョナルネットワーク及び日本とオーストラリア内の観測拠点からなる広域ネットワークから得られる電離圏・熱圏データと併せて研究を行った。これらの自動観測から得られるデータは、13に挙げる複数のホームページで公開し、共同研究を促進している。これらの観測から、(1)赤道熱圏・電離圏における大気波動の散逸(赤道上空での新たな南向き熱圏波動の発見、スマトラ沖地震で誘発された電離圏変動の発見など)、(2)赤道電離圏を介した南北中緯度電離圏の水平結合(伝搬性電離圏擾乱の磁気共役性の発見)、(3)赤道電離圏の電子密度擾乱(赤道プラズマバブル中の電離圏不規則構造の詳細構造の解析)、(4)プラズマバブル発生と対流圏活動との関係、などの数多くの新たな知見を得た。

  30. 中緯度熱圏大気波動の南北共役点観測

    研究課題/研究課題番号:13573006  2001年 - 2004年

    塩川 和夫

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    担当区分:研究分担者 

    ・平成13年7月に全天カメラ1式をアレシボ観測点(プエルトリコ)に持ち込み、アレシボにある大型レーダーと全天カメラによるTIDの同時観測を約2週間行った。この観測から、真夜中の赤道付近の電離層からやってくる1000kmスケールの大規模波動構造、200kmスケールの中規模伝搬性電離圏擾乱のそれぞれにっいて、レーダー・カメラ同時観測に成功した。
    ・平成13年10月に、日本の磁気共役点にあたるオーストラリアのダーウィンに、上記のカメラを設置し、定常観測を開始した。同年10-11月にかけて、赤道域で発生したプラズマバブルが、日本の鹿児島県佐多観測点とダーウィンで同時に観測された。詳細な解析から、この構造が日本とオーストラリアでちょうど鏡像の関係になっていることが見出され、赤道プラズマバブルの構造が、南北の磁力管をつないだ非常に大規模な構造であることがわかってきた。
    ・信楽・陸別で大気光イメージに観測された中規模伝搬性電離圏擾乱(MSTID)を統計的に解析し、その伝搬特性の季節変化、緯度変化を初めて明らかにした。さらに、DMSP衛星との同時観測例を詳しく調べることにより、MSTIDの波状構造に伴って電離層中に分極電場が生じていることを世界で初めて示した。
    ・平成14年8月9日に鹿児島県佐多岬とオーストラリアのダーウィンで、MSTIDの大気光イメージング観測に初めて成功した。その結果、MSTIDが磁気赤道をはさんで南北半球でちょうど対称の形をしており、南北半球で1対1に対応することがわかった。この事実は、MSTIDが電離層の分極電場の構造を持っており、その電場が磁力線を通じて南北に投影されていること、を示している。さらに平成15年5月21日から6月7日に第3回FRONTキャンペーン観測を行い、オーストラリア中央部のRenner Springs(滋賀県信楽町の磁気共役点)に新たに1台の大気光全天カメラを設置したほか、国内外計7カ所で全天カメラによる伝搬性電離圏擾乱の総合観測を行った。この観測から、中規模伝搬性電離圏擾乱が、非常に良い南北共役性をもち、南半球と北半球で対称な構造を保ちつつ伝搬していることがわかった。

  31. GPS受信機網による電離圏総電子数データ利用システムの構築

    研究課題/研究課題番号:12554016  2000年 - 2001年

    山本 衛

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    担当区分:研究分担者 

    国土地理院のGEONET全国約千地点のGPS受信機によって30秒毎に取得されている測位データを利用して、日本上空の電離圏全電子数(Total Electron Content : TEC)分布を水平分解能20km×時間分解能30秒で準リアルタイムに求め、その大量のデータを蓄積・提供するシステムを開発した。また全電子数データ利用プログラムやWWWを通じたクイックルック・プロット提供システムを開発し、全電子数データの扱いに詳しくない研究者でも利用可能な環境を整備した。更に、本研究によって蓄積される大量の全電子数データを用いて、電離圏TIDの分布・性質に関する統計解析や、太陽活動に伴う電離圏擾乱等の特徴的な太陽地球環境現象の研究をすすめた。
    まず、国土地理院GEONETの受信機のGPS観測データよりTECを求める手法の開発を行った。この際、観測されている視線方向の量より鉛直方向の量への変換の誤差を抑えるため天頂角の小さい(30度または45度)データのみを使用した。これにより、0.15度x0.15度の空間分解能、30秒の時間分解能、2-4x10^<16>個/m^2の精度で日本上空のTECの2次元分布が求められた。この手法を用いて1999年4月以降の全GEONETデータについてTECの算出を行った。受信機ごとのTEC絶対値データ(ATECファイル)、TECデータ(バイアス未補正:TECファイル)と日本上空の2次元TEC絶対値分布(AGRIDファイル)、TEC変動成分分布(GRIDファイル)のデータとプロットを毎日作成するシステムを構築し、そのデータを逐次wwwサーバー(http://stegps.kugi.kyoto-u.ac.jp)を通して提供できるようにした。また、これらデータのプロット・ルーチンやプロット作成サービスも上記wwwにて提供できるようなシステムも構築した。

  32. 列島規模観測網による熱圏大気波動の立体的研究

    研究課題/研究課題番号:11440145  1999年 - 2002年

    小川 忠彦

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    担当区分:研究分担者 

    1.本研究課題により、平成12年7月より鹿児島県佐多岬で、平成13年10月にはオーストラリアのダーウィンで、それぞれ大気光全天カメラの定常観測を開始し、平成10年10月より北海道陸別町及び滋賀県信楽町で行われている全天カメラ観測とあわせて、4点の多点大気光同時定常観測を現在に至るまで継続している。また、平成11年8月には沖縄県国頭村で、平成14年8月には鹿児島県種子島で、全天カメラによるキャンペーン観測を行っている。
    2.中間圏界面の大気重力波観測に関する成果は、a)日本列島及びオーストラリアにおいて、重力波の発生、伝搬特性の季節変化、緯度による違いを明らかにした、b)局在化した特異な重力波構造を発見し、それが重力波間の非線形相互作用により発生している可能性を示唆した、c)近接した2点同時重力波イメージング観測により、重力波及び大気光の発生高度を特定した。
    3.中規模伝搬性電離圏擾乱(MSTID)に関する成果は、a)日本でのMSTIDの発生確率、季節変化を統計的に明らかにした、b)人工衛星との比較観測、背景風観測によるモデル計算との比較により、MSTIDが大気重力波ではなく電離層不安定に起因する電場構造として存在していることを初めて明らかにした、c)さらにオーストラリアと日本の同時観測により、この電場構造が南北両半球の磁力線を通して同じ構造をとっていることを初めて明らかにした。
    4.大規模伝搬性電離圏擾乱(LSTID)に関する成果は、a)磁気嵐中に大気光の増光を伴うLSTIDを特定し、その変動が熱圏の極向き中性風によって引き起こされていることを、モデル計算、中性風の直接観測などにより示した、b)極域のデータと比較することにより、この極向き中性風の発生が従来の簡単な考え方では説明できないことを示した。
    5.赤道域プラズマバブルに関する成果は、日本付近の緯度でもプラズマバブルが観測されることを示し、日本とオーストラリアの同時観測から、このバブル構造が赤道をはさんで対称になっていることを初めて明らかにした。
    6.低緯度オーロラに関する成果は、平成11年から14年度において、11回の低緯度オーロラ観測に成功した。このうち平成13年3月31日と11月24日の低緯度オーロラは、北海道だけでなく滋賀県でも観測に成功し、科学機器で観測された低緯度オーロラの日本最南端記録となった。
    7.中間圏、熱圏の中性風観測に関する成果は、ファブリ・ペロー分光器の定常観測化に成功し、MUレーダーによる風速観測との比較により、大気光の発光高度の時間変化を明らかにしている。
    8.これらの成果は、以下に示す論文として出版しているので、詳しくはそちらを参照されたい。また、定常観測により得られたデータは、http://stdb2.stelab.nagoya-u.ac.jp/omti/ですべて公開し、共同研究の推進に役立てている

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担当経験のある科目 (本学) 6

  1. 電離圏物理学

    2017

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    本講義は電離圏の物理を理解することを目指している。中性大気との衝突が起こる電離圏中でのプラズマの運動や電離圏電流についての基礎知識を養う。また、電離圏に起こる諸現象についての観測結果や基本的な理論を学ぶ。また、電波を用いた電離圏の観測手法についても学ぶ。

  2. 電離圏物理学

    2016

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    本講義は電離圏の物理を理解することを目指している。中性大気との衝突が起こる電離圏中でのプラズマの運動や電離圏電流についての基礎知識を養う。また、電離圏に起こる諸現象についての観測結果や基本的な理論を学ぶ。また、電波を用いた電離圏の観測手法についても学ぶ。

  3. 電離圏物理学

    2015

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    本講義は電離圏の物理を理解することを目指している。中性大気との衝突が起こる電離圏中でのプラズマの運動や電離圏電流についての基礎知識を養う。また、電離圏に起こる諸現象についての観測結果や基本的な理論を学ぶ。また、電波を用いた電離圏の観測手法についても学ぶ。

  4. 電離圏物理学

    2014

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    本講義は電離圏の物理を理解することを目指している。中性大気との衝突が起こる電離圏中でのプラズマの運動や電離圏電流についての基礎知識を養う。また、電離圏に起こる諸現象についての観測結果や基本的な理論を学ぶ。また、電波を用いた電離圏の観測手法についても学ぶ。

  5. 電離圏物理学

    2013

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    本講義は電離圏の物理を理解することを目指している。中性大気との衝突が起こる電離圏中でのプラズマの運動や電離圏電流についての基礎知識を養う。また、電離圏に起こる諸現象についての観測結果や基本的な理論を学ぶ。また、電波を用いた電離圏の観測手法についても学ぶ。

  6. 電離圏物理学

    2012

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    本講義は電離圏の物理を理解することを目指している。中性大気との衝突が起こる電離圏中でのプラズマの運動や電離圏電流についての基礎知識を養う。また、電離圏に起こる諸現象についての観測結果や基本的な理論を学ぶ。また、電波を用いた電離圏の観測手法についても学ぶ。

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担当経験のある科目 (本学以外) 1

  1. 中・低緯度電離圏擾乱の電波・光学観測

    2013年4月 - 2014年3月 京都大学)

 

社会貢献活動 1

  1. 出前授業

    2015年11月

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    11月13日(金)に北海道陸別町の陸別小学校と陸別中学校で、本研究所及び北海道大学、北見工業大学の教員と大学院生による出前授業が実施されました。本研究所からは大塚雄一准教授と4名の大学院生が参加し、出前授業「夜空が光る?大気光について」によって、夕焼けが赤く見える仕組みなどを説明しました。また、翌14日(土)にはりくべつ宇宙地球科学館・銀河の森天文台において市民の皆さんを対象とした科学イベント「驚き!おもしろ科学実験2015」が実施され、直径1メートルの半球型スクリーンに地球や惑星の映像を投影する科学実験「動かしてみよう、四次元地球儀」を行いました。この事業は本研究所が事務局を務める陸別社会連携連絡協議会の活動の一環として、本学の総長裁量経費(地域貢献戦略枠)の支援のもとで実施されたものです。