研究者詳細 - 大塚　雄一

論文 - 大塚　雄一

分割表示 484 件中 241 - 260 件目／全件表示 >>

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

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

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

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

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

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

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

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

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

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

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

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

EARTH PLANETS AND SPACE 66 巻 2014年12月

CME front and severe space weather 査読有り

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

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

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

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

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

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

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

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

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

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

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

Auroral fragmentation into patches 査読有り

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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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