研究者詳細 - 大塚　雄一

論文 - 大塚　雄一

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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

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

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

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

Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL 査読有り Open Access

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

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

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

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

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

Nighttime-like quasi periodic echoes induced by a partial solar eclipse 査読有り Open Access

Thampi, SV; Yamamoto, M; Liu, HX; Saito, S; Otsuka, Y; Patra, AK

GEOPHYSICAL RESEARCH LETTERS 37 巻 2010年5月

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

Li, GZ; Ning, BQ; Hu, LH; Liu, LB; Yue, XA; Wan, WX; Zhao, BQ; Igarashi, K; Kubota, M; Otsuka, Y; Xu, JS; Liu, JY

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 115 巻 ( 4 ) 2010年4月

A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 査読有り Open Access

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

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

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

A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 査読有り Open Access

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

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

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

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

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

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

DOI： 10.1029/2009JA014297

Scopus

Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL 査読有り Open Access

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

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

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

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 Open Access

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

Thermospheric temperature and density variations 査読有り Open Access

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

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

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

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