研究者詳細 - 大塚　雄一

論文 - 大塚　雄一

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Lower-thermospheric wind fluctuations measured with an FPI during pulsating aurora at Tromso, Norway 査読有り

Oyama, S; Shiokawa, K; Kurihara, J; Tsuda, TT; Nozawa, S; Ogawa, Y; Otsuka, Y; Watkins, BJ

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

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

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

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

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

The STEL induction magnetometer network for observation of high-frequency geomagnetic pulsations 査読有り

Shiokawa, K; Nomura, R; Sakaguchi, K; Otsuka, Y; Hamaguchi, Y; Satoh, M; Katoh, Y; Yamamoto, Y; Shevtsov, BM; Smirnov, S; Poddelsky, I; Connors, M

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

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

Thermospheric temperature and density variations 査読有り

Fujiwara, H; Miyoshi, Y; Jin, H; Shinagawa, H; Otsuka, Y; Saito, A; Ishii, M

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

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

Hasbi, AM; Momani, MA; Ali, MAM; Misran, N; Shiokawa, K; Otsuka, Y; Yumoto, K

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

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

First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite 査読有り

Thampi, SV; Yamamoto, M; Tsunoda, RT; Otsuka, Y; Tsugawa, T; Uemoto, J; Ishii, M

GEOPHYSICAL RESEARCH LETTERS 36 巻 2009年9月

Coordinated observations of nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow and HF radar echoes at midlatitudes 査読有り

Suzuki, S; Hosokawa, K; Otsuka, Y; Shiokawa, K; Ogawa, T; Nishitani, N; Shibata, TF; Koustov, AV; Shevtsov, BM

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 114 巻頁： A07312 2009年7月

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

Onishi, T; Tsugawa, T; Otsuka, Y; Berthelier, JJ; Lebreton, JP

GEOPHYSICAL RESEARCH LETTERS 36 巻 2009年6月

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

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

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

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.

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

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.

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

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

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

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

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

Unusually elongated, bright airglow plume in the polar cap F region: Is it a tongue of ionization? 査読有り

Hosokawa, K; Tsugawa, T; Shiokawa, K; Otsuka, Y; Ogawa, T; Hairston, MR

GEOPHYSICAL RESEARCH LETTERS 36 巻 2009年4月

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

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

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

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