2021/03/30 更新

写真a

ノセ マサヒト
能勢 正仁
NOSÉ Masahito
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
大学院工学研究科
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(理学) ( 1998年3月   京都大学 ) 

研究キーワード 4

  1. 宇宙惑星科学

  2. 超高層物理学

  3. 宇宙空間物理学

  4. 地球電磁気学

研究分野 2

  1. 情報通信 / データベース  / 情報地球物理学

  2. 自然科学一般 / 宇宙惑星科学  / 宇宙空間物理学、地球電磁気学、超高層物理学

現在の研究課題とSDGs 1

  1. 宇宙環境擾乱現象の発生機構解明およびその予測

経歴 6

  1. 名古屋大学   宇宙地球環境研究所   准教授

    2018年8月 - 現在

  2. 京都大学   理学研究科附属地磁気世界資料解析センター   助教

    2007年4月 - 2018年7月

  3. 京都大学   理学研究科附属地磁気世界資料解析センター   助手

    2001年4月 - 2007年3月

  4. ジョンズホプキンス大学   応用物理研究所   研究員

    1998年7月 - 2001年3月

  5. 京都大学大学院理学研究科・研修員

    1998年4月 - 1998年6月

  6. 日本学術振興会特別研究員

    1996年4月 - 1998年3月

▼全件表示

学歴 3

  1. 京都大学   理学研究科   地球惑星科学専攻

    1995年4月 - 1998年3月

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    国名: 日本国

  2. 京都大学   理学研究科   地球物理学専攻

    1993年4月 - 1995年3月

  3. 京都大学   理学部

    1989年4月 - 1993年3月

所属学協会 3

  1. 地球電磁気・地球惑星圏学会

  2. 日本地球惑星科学連合

  3. アメリカ地球物理学連合(American Geophysicul Union)

受賞 1

  1. 大林奨励賞(第24号)

    2006年11月   地球電磁気・地球惑星圏学会   ウェーブレット関数を用いたPi2脈動の自動検出手法の開発とその応用研究

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    受賞区分:国内学会・会議・シンポジウム等の賞  受賞国:日本国

 

論文 135

  1. Magnetic Conjugacy of Pc1 Waves and Isolated Proton Precipitation at Subauroral Latitudes: Importance of Ionosphere as Intensity Modulation Region

    Ozaki M.

    Geophysical Research Letters   48 巻 ( 5 )   2021年3月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    DOI: 10.1029/2020GL091384

    Scopus

  2. Oxygen torus and its coincidence with EMIC wave in the deep inner magnetosphere: Van Allen Probe B and Arase observations

    Nose M., Matsuoka A., Kumamoto A., Kasahara Y., Teramoto M., Kurita S., Goldstein J., Kistler L. M., Singh S., Gololobov A., Shiokawa K., Imajo S., Oimatsu S., Yamamoto K., Obana Y., Shoji M., Tsuchiya F., Shinonara I, Miyoshi Y., Kurth W. S., Kletzing C. A., Smith C. W., MacDowal R. J., Spence H., Reeves G. D.

    EARTH PLANETS AND SPACE   72 巻 ( 1 )   2020年8月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-020-01235-w

    Web of Science

    Scopus

  3. Arase Observation of the Source Region of Auroral Arcs and Diffuse Auroras in the Inner Magnetosphere

    Shiokawa K., Nose M., Imajo S., Tanaka Y. -M., Miyoshi Y., Hosokawa K., Connors M., Engebretson M., Kazama Y., Wang S. -Y., Tam S. W. Y., Chang Tzu-Fang, Wang Bo-Jhou, Asamura K., Kasahara S., Yokota S., Hori T., Keika K., Kasaba Y., Shoji M., Kasahara Y., Matsuoka A., Shinohara I.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 8 )   2020年8月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2019JA027310

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  4. Penetration electric fields observed at middle and low latitudes during the 22 June 2015 geomagnetic storm

    Hashimoto Kumiko K., Kikuchi Takashi, Tomizawa Ichiro, Hosokawa Keisuke, Chum Jaroslav, Buresova Dalia, Nose Masahito, Koga Kiyokazu

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

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-020-01196-0

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  5. Evolution of field-aligned current in the meridional plane during substorm: multipoint observations from satellites and ground stations

    Imajo Shun, Nose Masahito, Aida Mari, Higashio Nana, Matsumoto Haruhisa, Kiyokazu Koga, Smith Charles, MacDowall Robert J., Yoshikawa Akimasa

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

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-020-01182-6

    Web of Science

    Scopus

  6. On the Transition Between the Inner and Outer Plasma Sheet in the Earth's Magnetotail

    Miyashita Yukinaga, Seki Kanako, Sakaguchi Kaori, Hiraki Yasutaka, Nose Masahito, Machida Shinobu, Saito Yoshifumi, Paterson William R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 4 )   2020年4月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2019JA027561

    Web of Science

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  7. Selective Acceleration of O+ by Drift-Bounce Resonance in the Earth's Magnetosphere: MMS Observations

    Oimatsu S., Nose M., Le G., Fuselier S. A., Ergun R. E., Lindqvist P. -A., Sormakov D.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 2 )   2020年2月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2019JA027686

    Web of Science

  8. Eastward Propagating Second Harmonic Poloidal Waves Triggered by Temporary Outward Gradient of Proton Phase Space Density: Van Allen Probe A Observation

    Yamamoto K., Nose M., Keika K., Hartley D. P., Smith C. W., MacDowall R. J., Lanzerotti L. J., Mitchell D. G., Spence H. E., Reeves G. D., Wygant J. R., Bonnell J. W., Oimatsu S.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 12 ) 頁: 9904 - 9923   2019年12月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2019JA027158

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  9. Remote Detection of Drift Resonance Between Energetic Electrons and Ultralow Frequency Waves: Multisatellite Coordinated Observation by Arase and Van Allen Probes

    Teramoto M., Hori T., Saito S., Miyoshi Y., Kurita S., Higashio N., Matsuoka A., Kasahara Y., Kasaba Y., Takashima T., Nomura R., Nose M., Fujimoto A., Tanaka Y. -M., Shoji M., Tsugawa Y., Shinohara M., Shinohara I., Blake J. B., Fennell J. F., Claudepierre S. G., Turner D. L., Kletzing C. A., Sormakov D., Troshichev O.

    GEOPHYSICAL RESEARCH LETTERS   46 巻 ( 21 ) 頁: 11642 - 11651   2019年11月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    DOI: 10.1029/2019GL084379

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  10. Locally Generated ULF Waves in the Martian Magnetosphere: MAVEN Observations

    Harada Y., Ruhunusiri S., Halekas J. S., Espley J., DiBraccio G. A., Mcfadden J. P., Mitchell D. L., Mazelle C., Collinson G., Brain D. A., Hara T., Nose M., Oimatsu S., Yamamoto K., Jakosky B. M.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 11 ) 頁: 8707 - 8726   2019年11月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2019JA027312

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  11. Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images (vol 70, 73, 2018)

    Ieda Akimasa, Kauristie Kirsti, Nishimura Yukitoshi, Miyashita Yukinaga, Frey Harald U., Juusola Liisa, Whiter Daniel, Nose Masahito, Fillingim Matthew O., Honary Farideh, Rogers Neil C., Miyoshi Yoshizumi, Miura Tsubasa, Kawashima Takahiro, Machida Shinobu

    EARTH PLANETS AND SPACE   71 巻 ( 1 )   2019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:Earth, Planets and Space  

    DOI: 10.1186/s40623-019-1053-3

    Web of Science

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  12. Meridional Distribution of Middle-Energy Protons and Pressure-Driven Currents in the Nightside Inner Magnetosphere: Arase Observations

    Imajo S., Nose M., Kasahara S., Yokota S., Matsuoka A., Keika K., Hori T., Teramoto M., Yamamoto K., Oimatsus S., Nomura R., Fujimoto A., Shinohara I, Miyoshi Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   124 巻 ( 7 ) 頁: 5719 - 5733   2019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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2019JA026682

    Web of Science

    Scopus

  13. The Space Physics Environment Data Analysis System (SPEDAS)

    Angelopoulos V., Cruce P., Drozdov A., Grimes E. W., Hatzigeorgiu N., King D. A., Larson D., Lewis J. W., McTiernan J. M., Roberts D. A., Russell C. L., Hori T., Kasahara Y., Kumamoto A., Matsuoka A., Miyashita Y., Miyoshi Y., Shinohara I., Teramoto M., Faden J. B., Halford A. J., McCarthy M., Millan R. M., Sample J. G., Smith D. M., Woodger L. A., Masson A., Narock A. A., Asamura K., Chang T. F., Chiang C. -Y., Kazama Y., Keika K., Matsuda S., Segawa T., Seki K., Shoji M., Tam S. W. Y., Umemura N., Wang B. -J., Wang S. -Y., Redmon R., Rodriguez J. V., Singer H. J., Vandegriff J., Abe S., Nose M., Shinbori A., Tanaka Y. -M., UeNo S., Andersson L., Dunn P., Fowler C., Halekas J. S., Hara T., Harada Y., Lee C. O., Lillis R., Mitchell D. L., Argall M. R., Bromund K., Burch J. L., Cohen I. J., Galloy M., Giles B., Jaynes A. N., Le Contel O., Oka M., Phan T. D., Walsh B. M., Westlake J., Wilder F. D., Bale S. D., Livi R., Pulupa M., Whittlesey P., DeWolfe A., Harter B., Lucas E., Auster U., Bonnell J. W., Cully C. M., Donovan E., Ergun R. E., Frey H. U., Jackel B., Keiling A., Korth H., McFadden J. P., Nishimura Y., Plaschke F., Robert P., Turner D. L., Weygand J. M., Candey R. M., Johnson R. C., Kovalick T., Liu M. H., McGuire R. E., Breneman A., Kersten K., Schroeder P.

    SPACE SCIENCE REVIEWS   215 巻 ( 1 )   2019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: 10.1007/s11214-018-0576-4

    Web of Science

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  14. Special issue "The 13th International Conference on Substorms" PREFACE

    LaBelle James, Lessard Marc, Nose Masahito, Raeder Joachim

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

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1186/s40623-019-0990-1

    Web of Science

    Scopus

  15. Visualization of rapid electron precipitation via chorus element wave-particle interactions

    Ozaki Mitsunori, Miyoshi Yoshizumi, Shiokawa Kazuo, Hosokawa Keisuke, Oyama Shin-ichiro, Kataoka Ryuho, Ebihara Yusuke, Ogawa Yasunobu, Kasahara Yoshiya, Yagitani Satoshi, Kasaba Yasumasa, Kumamoto Atsushi, Tsuchiya Fuminori, Matsuda Shoya, Katoh Yuto, Hikishima Mitsuru, Kurita Satoshi, Otsuka Yuichi, Moore Robert C., Tanaka Yoshimasa, Nose Masahito, Nagatsuma Tsutomu, Nishitani Nozomu, Kadokura Akira, Connors Martin, Inoue Takumi, Matsuoka Ayako, Shinohara Iku

    NATURE COMMUNICATIONS   10 巻 ( 1 ) 頁: 257   2019年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41467-018-07996-z

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    PubMed

  16. 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)     頁: .   2019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

  17. Microscopic Observations of Pulsating Aurora Associated With Chorus Element Structures: Coordinated Arase Satellite-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., Katoh Y., Hikishima M., Kumamoto A., Tsuchiya F., Kadokura A., Nishiyama T., Inoue T., Imamura K., Matsuoka A., Shinohara I.

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

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018GL079812

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    Scopus

  18. Ion Energies Dominating Energy Density in the Inner Magnetosphere: Spatial Distributions and Composition, Observed by Arase/MEP-i 査読有り

    Keika K., Kasahara S., Yokota S., Hoshino M., Seki K., Nose M., Amano T., Miyoshi Y., Shinohara I.

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 22 ) 頁: 12153 - 12162   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)   出版者・発行元:Geophysical Research Letters  

    DOI: 10.1029/2018GL080047

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  19. Magnetosphere-Ionosphere Connection of Storm-Time Region-2 Field-Aligned Current and Ring Current: Arase and AMPERE Observations 査読有り

    Imajo S., Nose M., Matsuoka A., Kasahara S., Yokota S., Teramoto M., Keika K., Motoba T., Anderson B., Nomura R., Fujimoto A., Shinohara I, Miyoshi Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 11 ) 頁: 9545 - 9559   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)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2018JA025865

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  20. Purple Auroral Rays and Global Pc1 Pulsations Observed at the CIR-Associated Solar Wind Density Enhancement on 21 March 2017

    Shiokawa K., Ozaki M., Kadokura A., Endo Y., Sakanoi T., Kurita S., Miyoshi Y., Oyama S. -I., Connors M., Schofield I., Ruohoniemi J. M., Nose M., Nagatsuma T., Sakaguchi K., Baishev D. G., Pashinin A., Rakhmatulin R., Shevtsov B., Poddelsky I., Engebretson M., Raita Tero, Tanaka Y. -M., Shinohara M., Teramoto M., Nomura R., Fujimoto A., Matsuoka A., Higashio N., Takashima T., Shinohara I., Albert Jay M.

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 20 ) 頁: 10819-10828   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2018GL079103

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  21. Longitudinal Structure of Oxygen Torus in the Inner Magnetosphere: Simultaneous Observations by Arase and Van Allen Probe A 査読有り

    Nose M., Matsuoka A., Kumamoto A., Kasahara Y., Goldstein J., Teramoto M., Tsuchiya F., Matsuda S., Shoji M., Imajo S., Oimatsu S., Yamamoto K., Obana Y., Nomura R., Fujimoto A., Shinohara I., Miyoshi Y., Kurth W. S., Kletzing C. A., Smith C. W., MacDowall R. J.

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 19 ) 頁: 10177 - 10184   2018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:American Geophysical Union ({AGU})  

    DOI: 10.1029/2018GL080122

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  22. Magnetic Field Dipolarization and Its Associated Ion Flux Variations in the Dawnside Deep Inner Magnetosphere: Arase Observations 査読有り

    Nose M., Matsuoka A., Kasahara S., Yokota S., Teramoto M., Keika K., Yamamoto K., Nomura R., Fujimoto A., Higashio N., Koshiishi H., Imajo S., Oimatsu S., Tanaka Y. -M., Shinohara M., Shinohara I., Miyoshi Y.

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 16 ) 頁: 7942 - 7950   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)   出版者・発行元:American Geophysical Union ({AGU})  

    DOI: 10.1029/2018GL078825

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  23. Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator 査読有り

    Takahashi Kazue, Denton Richard E., Motoba Tetsuo, Matsuoka Ayako, Kasaba Yasumasa, Kasahara Yoshiya, Teramoto Mariko, Shoji Masafumi, Takahashi Naoko, Miyoshi Yoshizumi, Nose Masahito, Kumamoto Atsushi, Tsuchiya Fuminori, Redmon Robert J., Rodriguez Juan V.

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 16 ) 頁: 7918 - 7926   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)   出版者・発行元:Geophysical Research Letters  

    DOI: 10.1029/2018GL078731

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  24. Drift-Bounce Resonance Between Pc5 Pulsations and Ions at Multiple Energies in the Nightside Magnetosphere: Arase and MMS Observations 査読有り

    Oimatsu S., Nose M., Teramoto M., Yamamoto K., Matsuoka A., Kasahara S., Yokota S., Keika K., Le G., Nomura R., Fujimoto A., Sormakov D., Troshichev O., Tanaka Y. -M., Shinohara M., Shinohara I., Miyoshi Y., Slavin J. A., Ergun R. E., Lindqvist P. -A.

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 15 ) 頁: 7277 - 7286   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)   出版者・発行元:American Geophysical Union ({AGU})  

    DOI: 10.1029/2018GL078961

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  25. Giant Pulsations Excited by a Steep Earthward Gradient of Proton Phase Space Density: Arase Observation 査読有り

    Yamamoto Kazuhiro, Nose Masahito, Kasahara Satoshi, Yokota Shoichiro, Keika Kunihiro, Matsuoka Ayako, Teramoto Mariko, Takahashi Kazue, Oimatsu Satoshi, Nomura Reiko, Vellante Massimo, Heilig Balazs, Fujimoto Akiko, Tanaka Yoshimasa, Shinohara Manabu, Shinohara Iku, Miyoshi Yoshizumi

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 14 ) 頁: 6773 - 6781   2018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:American Geophysical Union ({AGU})  

    DOI: 10.1029/2018GL078293

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  26. Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images 査読有り

    Ieda Akimasa, Kauristie Kirsti, Nishimura Yukitoshi, Miyashita Yukinaga, Frey Harald U., Juusola Liisa, Whiter Daniel, Nose Masahito, Fillingim Matthew O., Honary Farideh, Rogers Neil C., Miyoshi Yoshizumi, Miura Tsubasa, Kawashima Takahiro, Machida Shinobu

    EARTH PLANETS AND SPACE   70 巻 ( 1 ) 頁: 73   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)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-018-0843-3

    Web of Science

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    PubMed

  27. Van Allen Probes Observations of Drift-Bounce Resonance and Energy Transfer Between Energetic Ring Current Protons and Poloidal Pc4 Wave 査読有り

    S. Oimatsu, M. Nosé, K. Takahashi, K. Yamamoto, K. Keika, C. A. Kletzing, C. W. Smith, R. J. MacDowall, D. G. Mitchell

    Journal of Geophysical Research: Space Physics   123 巻 ( 5 ) 頁: 3421 - 3435   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)   出版者・発行元:Blackwell Publishing Ltd  

    A poloidal Pc4 wave and proton flux oscillations are observed in the inner magnetosphere on the dayside near the magnetic equator by the Van Allen Probes spacecraft on 2 March 2014. The flux oscillations are observed in the energy range of 67.0 to 268.8 keV with the same frequency of the poloidal Pc4 wave. We find pitch angle and energy dispersion in the phase difference between the poloidal magnetic field and the proton flux oscillations, which are features of drift-bounce resonance. We estimate the resonance energy to be ~120 keV for pitch angle (α) of 30° or 150° and 170–180 keV for α = 50° or 130°. To examine the direction of energy flow between protons and the wave, we calculate the sign of the gradient of proton phase space density (df/dW) on both the inbound and outbound legs of the orbit. We find the gradient to be outward on both legs, which means that energy is transferred from the protons to the wave. During the poloidal Pc4 wave event, the Dst* index shows a measurable increase of ~6.7 nT. We estimate the total energy loss of the ring current from the recovery of the Dst* index and from the variation of proton flux by the drift-bounce resonance. We suggest that energy transfer from the ring current protons to the poloidal Pc4 wave via the drift-bounce resonance contributes to up to ~85% of the increase of the Dst* index.

    DOI: 10.1029/2017JA025087

    Scopus

  28. The ARASE (ERG) magnetic field investigation 査読有り

    Matsuoka Ayako, Teramoto Mariko, Nomura Reiko, Nose Masahito, Fujimoto Akiko, Tanaka Yoshimasa, Shinohara Manabu, Nagatsuma Tsutomu, Shiokawa Kazuo, Obana Yuki, Miyoshi Yoshizumi, Mita Makoto, Takashima Takeshi, Shinohara Iku

    EARTH PLANETS AND SPACE   70 巻 ( 1 )   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)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-018-0800-1

    Web of Science

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  29. Theory, modeling, and integrated studies in the Arase (ERG) project 査読有り

    Seki Kanako, Miyoshi Yoshizumi, Ebihara Yusuke, Katoh Yuto, Amano Takanobu, Saito Shinji, Shoji Masafumi, Nakamizo Aoi, Keika Kunihiro, Hori Tomoaki, Nakano Shin'ya, Watanabe Shigeto, Kamiya Kei, Takahashi Naoko, Omura Yoshiharu, Nose Masahito, Fok Mei-Ching, Tanaka Takashi, Ieda Akimasa, Yoshikawa Akimasa

    EARTH PLANETS AND SPACE   70 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)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-018-0785-9

    Web of Science

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  30. Van Allen Probes Observations of Second Harmonic Poloidal Standing Alfvén Waves 査読有り

    Kazue Takahashi, Satoshi Oimatsu, Masahito Nos{\'{e, Kyungguk Min, Seth G. Claudepierre, Anthony Chan, John Wygant, Hyomin Kim

    Journal of Geophysical Research: Space Physics   123 巻 ( 1 ) 頁: 611 - 637   2018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:American Geophysical Union ({AGU})  

    DOI: 10.1002/2017JA024869

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  31. Three-Step Buildup of the 17 March 2015 Storm Ring Current: Implication for the Cause of the Unexpected Storm Intensification 査読有り

    Keika Kunihiro, Seki Kanako, Nose Masahito, Miyoshi Yoshizumi, Lanzerotti Louis J., Mitchell Donald G., Gkioulidou Matina, Manweiler Jerry W.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   123 巻 ( 1 ) 頁: 414 - 428   2018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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2017JA024462

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  32. Initial results of EMIC observation by MGF/Arase

    Nomura R., Matsuoka A., Teramoto M., Miyoshi Y., Matsuda S., Kurita S., Keika K., Nose M., Shoji M., Fujimoto A., Shinohara M., Tanaka Y., Kasahara Y., Kasaba Y., Ishisaka K.

    2018 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC)     頁: .   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

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

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

    EARTH PLANETS AND SPACE   69 巻 ( 1 )   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:Earth, Planets and Space  

    DOI: 10.1186/s40623-017-0745-9

    Web of Science

    Scopus

  34. 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)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2017JA024342

    Web of Science

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  35. Ionospheric Alfvén resonator observed at low-latitude ground station, Muroto 査読有り

    M. Nos{\'{e, M. Uyeshima, J. Kawai, H. Hase

    Journal of Geophysical Research: Space Physics   122 巻 ( 7 ) 頁: 7240 - 7255   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:American Geophysical Union ({AGU})  

    DOI: 10.1002/2017JA024204

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  36. Long-term variations in the plasma sheet ion composition and substorm occurrence over 23 years 査読有り

    Masahito Nos

    Geoscience Letters   3 巻 ( 1 )   2016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:Springer Science $\mathplus$ Business Media  

    DOI: 10.1186/s40562-015-0033-0

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  37. Van Allen Probes observations of magnetic field dipolarization and its associated O+ flux variations in the inner magnetosphere at L < 6.6 査読有り

    Nose M., Keika K., Kletzing C. A., Spence H. E., Smith C. W., MacDowall R. J., Reeves G. D., Larsen B. A., Mitchell D. G.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 8 ) 頁: 7572 - 7589   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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2016JA022549

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  38. Storm time impulsive enhancements of energetic oxygen due to adiabatic acceleration of preexisting warm oxygen in the inner magnetosphere 査読有り

    Keika Kunihiro, Seki Kanako, Nose Masahito, Machida Shinobu, Miyoshi Yoshizumi, Lanzerotti Louis J., Mitchell Donald G., Gkioulidou Matina, Turner Drew, Spence Harlan, Larsen Brian A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 8 ) 頁: 7739 - 7752   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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2016JA022384

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  39. Estimation of magnetospheric plasma ion composition for 1956-1975 by using high time resolution geomagnetic field data created from analog magnetograms 査読有り

    K. Yamamoto, M. Nose, N. Mashiko, K. Morinaga, S. Nagamachi

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 6 ) 頁: 5203 - 5212   2016年6月

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

    This study addresses the ion composition in the magnetosphere before the satellite era. We estimate the plasma ion mass for 1956-1975 from the period of low-latitude Pi2 pulsations found in digital geomagnetic field data that are created from analog magnetograms at Kakioka. The period of investigation covers most of solar cycle 19 and the whole solar cycle 20. To consider long-term variation, the moving average of the estimated plasma ion mass is calculated with a 1 year time window. We find that 1 year moving average of the plasma ion mass changed by a factor of similar to 2 during one solar cycle (i.e., between similar to 1.1 amu and similar to 2.4 amu for solar cycle 19 and between similar to 1.1 amu and similar to 2.0 amu for solar cycle 20). The correlation coefficient between the 1 year moving average of the plasma ion mass and that of the F-10.7 index is 0.86. This result supports the idea that in long-term variation, solar radiation increases the density and the temperature of O+ ions in the ionosphere, leads to the outflow of O+ ions, and contributes to the enhancement of the plasma ion mass in the nightside magnetosphere. The digital data created from analog magnetograms provide an important clue to know the space environment in old days and are advantageous for studies of the space weather and space climate.

    DOI: 10.1002/2016JA022510

    Web of Science

  40. Subpacket structures in EMIC rising tone emissions observed by the THEMIS probes 査読有り

    Satoko Nakamura, Yoshiharu Omura, Masafumi Shoji, Masahito Nose, Danny Summers, Vassilis Angelopoulos

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 9 ) 頁: 7318 - 7330   2015年9月

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

    We report subpacket structures found in electromagnetic ion cyclotron (EMIC) rising tone emissions observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes. We investigate three typical cases in detail. The first case shows a continuous single rising tone with four obvious subpackets, and the second case is characterized by a patchy emission with multiple subpackets triggered in a broadband frequency. The third case looks like a smooth rising tone without any obvious subpacket in the fast Fourier transform spectrum, while its amplitude contains small peaks with increasing frequencies. The degree of polarization of each subpacket is generally higher than 0.8 with a left-handed polarization, and the wave direction of the subpackets is typically field aligned. We show that the time evolution of the observed frequency and amplitude can be reproduced consistently by nonlinear growth theory. We also compare the observed time span of each subpacket structure with the theoretical trapping time for second-order cyclotron resonance. They are consistent, indicating that an individual subpacket is generated through a nonlinear wave growth process which excites an element in accordance with the theoretically predicted optimum amplitude.

    DOI: 10.1002/2014JA020764

    Web of Science

  41. Multipoint observation of the response of the magnetosphere and ionosphere related to the sudden impulse event on 19 November 2007 査読有り

    Antoni Segarra, Masahito Nose, Juan Jose Curto, Tohru Araki

    JOURNAL OF SPACE WEATHER AND SPACE CLIMATE   5 巻   2015年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EDP SCIENCES S A  

    The aim of this study is to provide a complete scope of a magnetic sudden impulse (SI) event along its way through interplanetary space and the magnetosphere until its arrival to the ground. In our case, we chose the event of 19th November 2007 because of the availability of enough well-located spacecraft at that moment for our purpose. We have used a 16 spacecraft data set. We calculated the mass flux variation and the change in magnetic field components across the discontinuity. Thus, we identified the solar wind discontinuity as a shock. We also calculated the orientation of the solar wind shock front. Then, we examined the effects of the shock front propagation in detail. With this large data set, we obtained a global view of the travelling wave front and identified the effects of the compressional wave front. Thus, we determined in detail the shock front passing through the different parts of the magnetosphere. We described the compressional effects in the bow shock, the magnetosheath, and the magnetopause and we depicted the propagation inside the inner magnetosphere. Moreover, we used an extensive data set from magnetic observatories on the ground and so we studied the global distribution of the SI waveform. Finally, the comparison of the observational facts with those derived from the theoretical model showed a good consistency. On the basis of the waveforms and polarizations of this SI, we determined the location in latitude where ionospheric currents (ICs) changed their sense. And also, we related polarization at ground to polarization measured by GOES spacecraft.

    DOI: 10.1051/swsc/2015016

    Web of Science

  42. Spatial structure and temporal evolution of energetic particle injections in the inner magnetosphere during the 14 July 2013 substorm event 査読有り

    Matina Gkioulidou, S. Ohtani, D. G. Mitchell, A. Y. Ukhorskiy, G. D. Reeves, D. L. Turner, J. W. Gjerloev, M. Nose, K. Koga, J. V. Rodriguez, L. J. Lanzerotti

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 3 ) 頁: 1924 - 1938   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  

    Recent results by the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit could be very frequent throughout the main phase of a geomagnetic storm. Understanding, therefore, the formation and evolution of energetic particle injections is critical in order to quantify their effect in the inner magnetosphere. We present a case study of a substorm event that occurred during a weak storm (Dst similar to-40nT) on 14 July 2013. Van Allen Probe B, inside geosynchronous orbit, observed two energetic proton injections within 10min, with different dipolarization signatures and duration. The first one is a dispersionless, short-timescale injection pulse accompanied by a sharp dipolarization signature, while the second one is a dispersed, longer-timescale injection pulse accompanied by a gradual dipolarization signature. We combined ground magnetometer data from various stations and in situ particle and magnetic field data from multiple satellites in the inner magnetosphere and near-Earth plasma sheet to determine the spatial extent of these injections, their temporal evolution, and their effects in the inner magnetosphere. Our results indicate that there are different spatial and temporal scales at which injections can occur in the inner magnetosphere and depict the necessity of multipoint observations of both particle and magnetic field data in order to determine these scales.

    DOI: 10.1002/2014JA020872

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  43. Formation of the oxygen torus in the inner magnetosphere: Van Allen Probes observations 査読有り

    Nose M., Oimatsu S., Keika K., Kletzing C. A., Kurth W. S., De Pascuale S., Smith C. W., MacDowall R. J., Nakano S., Reeves G. D., Spence H. E., Larsen B. A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 2 ) 頁: 1182 - 1196   2015年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2014JA020593

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  44. Responses of different ion species to fast plasma flows and local dipolarization in the plasma sheet 査読有り

    Ohtani S., Nose M., Miyashita Y., Lui A. T. Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 1 ) 頁: 187 - 200   2015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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2014JA020517

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  45. 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 ( 1 ) 頁: 1 - 20   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:Earth, Planets and Space  

    DOI: 10.1186/s40623-014-0155-1

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  46. An Interactive Data Language software package to calculate ionospheric conductivity by using numerical models 査読有り

    Koyamaa Yukinobu, Shinbori Atsuki, Tanaka Yoshimasa, Hori Tomoaki, Nose Masahito, Oimatsu Satoshi

    COMPUTER PHYSICS COMMUNICATIONS   185 巻 ( 12 ) 頁: 3398 - 3405   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:Computer Physics Communications  

    DOI: 10.1016/j.cpc.2014.08.011

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  47. Interuniversity Upper Atmosphere Global Observation NETwork (IUGONET) meta-database and analysis software

    Yatagai A.

    Data Science Journal   13 巻   頁: PDA37-PDA43   2014年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2481/dsj.IFPDA-07

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  48. Magnetic fluctuations embedded in dipolarization inside geosynchronous orbit and their associated selective acceleration of O+ ions 査読有り

    Nose M., Takahashi K., Keika K., Kistler L. M., Koga K., Koshiishi H., Matsumoto H., Shoji M., Miyashita Y., Nomura R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 6 ) 頁: 4639 - 4655   2014年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2014JA019806

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  49. Electromagnetic ion cyclotron rising tone emissions observed by THEMIS probes outside the plasmapause

    Nakamura Satoko, Omura Yoshiharu, Machida Shinobu, Shoji Masafumi, Nose Masahito, Angelopoulos Vassilis

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   119 巻 ( 3 ) 頁: 1874 - 1886   2014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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1002/2013JA019146

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  50. 専門知のための科学データ融合表示ツール

    村田 健史, 能勢 正仁, 岡田 雅樹, 小嶋 浩嗣, 山本 和憲, 鵜川 健太郎, 村永 和哉, 鈴木 豊, 渡邉 英伸, 是津 耕司, 北本 朝展, 篠原 育, 笠原 禎也

    情報知識学会誌   24 巻 ( 2 ) 頁: 118-124   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    本稿では,Web2.0で提案された集合知の概念を学術分野に拡張し,専門知・学術知を提案する.集合知ではインターネット上で一般市民からの情報を収集することで新しい情報を構築するのに対 し,専門知では異なる学術研究情報を融合し,一般社会に向けて情報を発信する.専門知においては,どのような情報をどのように集約し,提示するかが肝要となる.本研究では収集した科学データを融合して表示するための科学データ融合表示ツールを開発した.

    DOI: 10.2964/jsik_2014_007

    CiNii Article

  51. Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data 査読有り

    Machida S., Miyashita Y., Ieda A., Nose M., Angelopoulos V., McFadden J. P.

    ANNALES GEOPHYSICAE   32 巻 ( 2 ) 頁: 99 - 111   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:Annales Geophysicae  

    DOI: 10.5194/angeo-32-99-2014

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  52. 世界科学データシステム(WDS)のための学際的科学データ表示Webの提案

    村田 健史, 岡田 雅樹, 小嶋 浩嗣, 能勢 正仁, 木村 映善, 建部 修見, 田中 昌宏, 鵜川 健太郎, 村永 和哉, 鈴木 豊, 渡邉 英伸, 是津 耕司, 山本 和憲, 篠原 育, 笠原 禎也

    情報知識学会誌   24 巻 ( 3 ) 頁: 297-320   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    世界科学会議(ICSU)のプログラムの一つである世界科学データシステム(WDS)は科学データに関する国際的取組を目的としており,異分野横断型研究対応を主要目標の一つとして掲げている.NICTサイエンスクラウドは,WDSの理念を実現するために次世代型の科学研究環境の実現を目的に構築された科学研究用クラウドシステムである.科学分野のビッグデータの収集・転送機能,保存・公開機能,処理・可視化機能をマッシュアップすることで学際的研究環境の実現が期待される.本研究では,科学データを融合して表示するための学際的科学データ表示Webを提案する.過去の 経験をもとに,まず学際的科学データ表示Webで必要な要件をまとめた.さらに基本設計を行い, 2 つの科学衛星プロジェクトデータを融合表示するWebアプリケーションをNICTサイエンスクラウド上に実装した.この実装事例をもとに,学際的科学データ表示Webの有効性について議論する.

    DOI: 10.2964/jsik_2014_030

    CiNii Article

  53. Assessment of the auroral electrojet index performance under various geomagnetic conditions 査読有り

    K. Liou, K. Takahashi, B. J. Anderson, M. Nose, T. Iyemori

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   92 巻   頁: 31 - 36   2013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:PERGAMON-ELSEVIER SCIENCE LTD  

    Saturation of the auroral electrojet (AE) index during storm times is a phenomenon that has been known but not fully understood. To address this puzzle, here we correlate the (provisional) AE index with net field-aligned current (Net-dB) index, which is a data product derived with magnetic field measurements from the Iridium satellite constellation (Anderson et al., 2010), with an assumption that AE is largely measuring convection driven by the field-aligned currents represented by the Net-dB index. The Net-dB index has a time resolution of similar to 45 mm and is currently available from February 18, 1999, to May 31, 2008. It is found that, for the entire data period, there is a good linear correlation (r=0.74) between the AE index, when averaging over the Net-dB index time grids, and the Net-dB index, suggesting that statistically similar to 55% of the ionospheric Hall currents correlate with large scale convection as reflected in the field-aligned currents. It is also found that the correlation decreases during storm times, with a clear decreasing trend toward a more negative Sym-H. For large storms (Sym-H &lt; - 100 nT), the correlation becomes weak (r &lt; 0.4). Two correlation peaks are identified: a major peak (r=0.73) occurring at Sym-H &gt; 30 nT and a secondary peak (r=0.66) at Sym-H similar to -50 to -30 nT. A further study shows that the variations of the AE-Net-dB correlation are associated with the location of the field-aligned currents into and out of the ionosphere relative to the ground magnetometer stations, as expected often but not demonstrated in the past. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jastp.2012.09.017

    Web of Science

    J-GLOBAL

  54. Barometric and magnetic observations of vertical acoustic resonance and resultant generation of field-aligned current associated with earthquakes 査読有り

    Toshihiko Iyemori, Yoshikazu Tanaka, Yoko Odagi, Yasuharu Sano, Masahiko Takeda, Masahito Nose, Mitsuru Utsugi, Domingo Rosales, Edwin Choque, Jose Ishitsuka, Sadato Yamanaka, Kunihito Nakanishi, Mitsuru Matsumura, Hiroyuki Shinagawa

    EARTH PLANETS AND SPACE   65 巻 ( 8 ) 頁: 901 - 909   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    Three rare occasions are introduced, where the excitation of vertical acoustic resonance between the ground and the ionosphere, and the resultant generation of a field-aligned current, just after earthquakes are observationally confirmed. In the case of two inland earthquakes, barometric observations very close to the epicenters (i.e., only 30 km apart) were available, and they showed a sharp spectral peak which appeared within one hour after the origin time and lasted a few hours. The observed periods of the spectral peaks around 260 seconds are close to the period of the theoretically-expected fundamental mode of the resonance. On the other hand, magnetic observations on the ground showed a dominant period at 220-230 seconds which corresponds to the first overtone among theoretically-expected major resonance peaks. In the third case, i.e., during the 2010 Chile earthquake, a long-period magnetic oscillation in the east-west direction, which has two major resonance periods at 265 and 190-195 seconds, was observed on the night-side magnetic dip equator in Peru, where the distance is more than 2600 km from the epicenter, under a very quiet geomagnetic condition. The oscillation was interpreted as the effect of field-aligned current generated through a dynamo process in the ionosphere over the epicenter caused by the resonance.

    DOI: 10.5047/eps.2013.02.002

    Web of Science

    CiNii Article

    J-GLOBAL

  55. A statistical study of energy release and transport midway between the magnetic reconnection and initial dipolarization regions in the near-Earth magnetotail associated with substorm expansion onsets

    Miyashita Y., Machida S., Nose M., Liou K., Saito Y., Paterson W. R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻 ( 11 )   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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2012JA017925

    Web of Science

    Scopus

  56. Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude 査読有り

    M. Nose, T. Iyemori, L. Wang, A. Hitchman, J. Matzka, M. Feller, S. Egdorf, S. Gilder, N. Kumasaka, K. Koga, H. Matsumoto, H. Koshiishi, G. Cifuentes-Nava, J. J. Curto, A. Segarra, C. Celik

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   10 巻 ( 8 )   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  

    Geomagnetic field data with high time resolution (typically 1 s) have recently become more commonly acquired by ground stations. Such high time resolution data enable identifying Pi2 pulsations which have periods of 40-150 s and irregular (damped) waveforms. It is well-known that pulsations of this type are clearly observed at mid-and low-latitude ground stations on the nightside at substorm onset. Therefore, with 1-s data from multiple stations distributed in longitude around the Earth's circumference, substorm onset can be regularly monitored. In the present study we propose a new substorm index, the Wp index (Wave and planetary), which reflects Pi2 wave power at low-latitude, using geomagnetic field data from 11 ground stations. We compare the Wp index with the AE and ASY indices as well as the electron flux and magnetic field data at geosynchronous altitudes for 11 March 2010. We find that significant enhancements of the Wp index mostly coincide with those of the other data. Thus the Wp index can be considered a good indicator of substorm onset. The Wp index, other geomagnetic indices, and geosynchronous satellite data are plotted in a stack for quick and easy search of substorm onset. The stack plots and digital data of the Wp index are available at the Web site (http://s-cubed.info) for public use. These products would be useful to investigate and understand space weather events, because substorms cause injection of intense fluxes of energetic electrons into the inner magnetosphere and potentially have deleterious impacts on satellites by inducing surface charging. Citation: Nose, M., et al. (2012), Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude, Space Weather, 10, S08002, doi:10.1029/2012SW000785.

    DOI: 10.1029/2012SW000785

    Web of Science

  57. Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude 査読有り

    M. Nose, T. Iyemori, L. Wang, A. Hitchman, J. Matzka, M. Feller, S. Egdorf, S. Gilder, N. Kumasaka, K. Koga, H. Matsumoto, H. Koshiishi, G. Cifuentes-Nava, J. J. Curto, A. Segarra, C. Celik

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   10 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  

    Geomagnetic field data with high time resolution (typically 1 s) have recently become more commonly acquired by ground stations. Such high time resolution data enable identifying Pi2 pulsations which have periods of 40-150 s and irregular (damped) waveforms. It is well-known that pulsations of this type are clearly observed at mid-and low-latitude ground stations on the nightside at substorm onset. Therefore, with 1-s data from multiple stations distributed in longitude around the Earth's circumference, substorm onset can be regularly monitored. In the present study we propose a new substorm index, the Wp index (Wave and planetary), which reflects Pi2 wave power at low-latitude, using geomagnetic field data from 11 ground stations. We compare the Wp index with the AE and ASY indices as well as the electron flux and magnetic field data at geosynchronous altitudes for 11 March 2010. We find that significant enhancements of the Wp index mostly coincide with those of the other data. Thus the Wp index can be considered a good indicator of substorm onset. The Wp index, other geomagnetic indices, and geosynchronous satellite data are plotted in a stack for quick and easy search of substorm onset. The stack plots and digital data of the Wp index are available at the Web site (http://s-cubed.info) for public use. These products would be useful to investigate and understand space weather events, because substorms cause injection of intense fluxes of energetic electrons into the inner magnetosphere and potentially have deleterious impacts on satellites by inducing surface charging. Citation: Nose, M., et al. (2012), Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude, Space Weather, 10, S08002, doi:10.1029/2012SW000785.

    DOI: 10.1029/2012SW000785

    Web of Science

  58. Revisiting the role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization 査読有り

    M. Nose, Y. Ono, S. P. Christon, A. T. Y. Lui

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻 ( 2 )   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  

    Using energetic (9-212 keV/e) ion flux data obtained by the Geotail spacecraft, Ono et al. (2009) statistically examined changes in the energy density of H+ and O+ ions in the near-Earth plasma sheet during substorm-associated dipolarization. They found that ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies. The present paper revisits this result and finds it still holds.

    DOI: 10.1029/2012JA017518

    Web of Science

  59. Revisiting the role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization 査読有り

    M. Nose, Y. Ono, S. P. Christon, A. T. Y. Lui

    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  

    Using energetic (9-212 keV/e) ion flux data obtained by the Geotail spacecraft, Ono et al. (2009) statistically examined changes in the energy density of H+ and O+ ions in the near-Earth plasma sheet during substorm-associated dipolarization. They found that ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies. The present paper revisits this result and finds it still holds.

    DOI: 10.1029/2012JA017518

    Web of Science

  60. The Energization and Radiation in Geospace (ERG) Project

    Miyoshi Y., Ono T., Takashima T., Asamura K., Hirahara M., Kasaba Y., Matsuoka A., Kojima H., Shiokawa K., Seki K., Fujimoto M., Nagatsuma T., Cheng C. Z., Kazama Y., Kasahara S., Mitani T., Matsumoto H., Higashio N., Kumamoto A., Yagitani S., Kasahara Y., Ishisaka K., Blomberg L., Fujimoto A., Katoh Y., Ebihara Y., Omura Y., Nose M., Hori T., Miyashita Y., Tanaka Y. -M., Segawa T.

    DYNAMICS OF THE EARTH'S RADIATION BELTS AND INNER MAGNETOSPHERE   199 巻   頁: 103-116   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: 10.1029/2012GM001304

    Web of Science

    Scopus

  61. Energetic O+ and H+ ions in the plasma sheet: Implications for the transport of ionospheric ions 査読有り

    S. Ohtani, M. Nose, S. P. Christon, A. T. Y. Lui

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 10 )   2011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 present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O+ ions, and the characteristics of the H+ ions are used as references. The following is a summary of the results. (1) The average O+ energy is lower during solar maximum and higher during solar minimum. A similar tendency is also found for the average H+ energy, but only for geomagnetically active times; (2) The O+-to-H+ ratios of number and energy densities are several times higher during solar maximum than during solar minimum; (3) The average H+ and O+ energies and the O+-to-H+ ratios of number and energy densities all increase with geomagnetic activity. The differences among different solar phases not only persist but also increase with increasing geomagnetic activity; (4) Whereas the average H+ energy increases toward Earth, the average O+ energy decreases toward Earth. The average energy increases toward dusk for both the H+ and O+ ions; (5) The O+-to-H+ ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O+ ions is transported directly from the ionosphere to the near-Earth region rather than through the distant tail.

    DOI: 10.1029/2011JA016532

    Web of Science

  62. Oxygen torus in the deep inner magnetosphere and its contribution to recurrent process of O+-rich ring current formation 査読有り

    M. Nose, K. Takahashi, R. R. Anderson, H. J. Singer

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 10 )   2011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  

    Using the magnetic field and plasma wave data obtained by the Combined Release and Radiation Effects Satellite (CRRES), we search for enhancements of O+ ion density in the deep inner magnetosphere known as "the oxygen torus". We examine 4 events on the dayside in which toroidal standing Alfven waves appear clearly. From the frequency of the toroidal waves, the magnetospheric local mass density (rho(L)) is estimated by solving the MHD wave equation for realistic models of the magnetic field and the field line mass distribution. We also estimate the local electron number density (n(eL)) from the plasma wave spectrograms by identifying narrow-band emission at the upper-hybrid resonance frequency. Assuming the quasi-neutral condition of plasma, we infer the local average ion mass (M-L) by rho(L)/n(eL). It is found that M-L is approximately 3 amu in the plasma trough, while it shows an enhancement of &gt;7 amu at L similar to 4.5-6.5 that is close to the plasmapause at L similar to 3.5-6.0. This indicates an existence of the oxygen torus in the vicinity of the plasmapause. The oxygen torus is found preferentially during the storm recovery phase. We interpret that these features of the oxygen torus (i.e., close relations with the plasmapause and the storm recovery phase) reflect its generation mechanism; that is, the ionospheric temperature is enhanced by heat conduction from high altitudes in the limited L range where the plasmasphere, because of its inflation during the recovery phase, encounters the ring current, and then the ionosphere has a larger scale height and supplies O+ ions to the inner magnetosphere, resulting in the oxygen torus. We also discuss the contribution of the oxygen torus to the formation of the O+-rich ring current. It is proposed that the O+-rich ring current is formed in a recurrent process, in which the oxygen torus, the plasmasphere, and the ring current interact with each other.

    DOI: 10.1029/2011JA016651

    Web of Science

  63. Pi2 pulsations in the inner magnetosphere simultaneously observed by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer and Dynamics Explorer 1 satellites 査読有り

    M. Teramoto, K. Takahashi, M. Nose, D. -H. Lee, P. R. Sutcliffe

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 7 )   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  

    We statistically studied the spatial characteristics of Pi2 pulsations using magnetic field observations in the magnetosphere at the equatorial-orbiting Active Magnetospheric Particle Tracer Explorers (AMPTE)/Charge Composition Explorer (CCE) and the polar-orbiting Dynamics Explorer 1 (DE 1) satellites and on the ground at the low-latitude station Kakioka (KAK, L = 1.23). We defined Pi2 pulsations from wavelet analysis of KAK data covering August 1984 to January 1989 and obtained 849 nightside (20:00-04:00 LT) events. For each KAK Pi2 event, we evaluated the coherence between the ground H component and the magnetospheric radial (B(perpendicular to R)), azimuthal (B(perpendicular to A)), and compressional (B(//)) components at the frequency of the ground Pi2. High-coherence ground-satellite Pi2 events were found most often in B(//), with many of them evident at both spacecraft when CCE was located near the equator (magnetic latitude &lt;30 degrees) and inside of the plasmapause estimated from an empirical formula while DE 1 was located at high latitude (&gt;30 degrees) and outside of the estimated plasmapause. In these simultaneous CCE and DE 1 events, the B(//) amplitude was larger at CCE; in addition, the H-B(//) cross phase was similar to 0 degrees at CCE but was similar to 180 degrees at DE 1. We show detailed analysis of one such event as well as two other events that occurred when CCE was outside of the estimated plasmapause and exhibited different coherence and cross-phase properties at this spacecraft. Overall, the two-satellite observations provide additional evidence of plasmaspheric virtual resonance, which was previously suggested from studies using single satellites.

    DOI: 10.1029/2010JA016199

    Web of Science

  64. Magnetic field depression at the Earth's surface during energetic neutral atom emission fade-out in the inner magnetosphere 査読有り

    M. Nose, S. Ohtani, P. C. Son Brandt, T. Iyemori, K. Keika, D. -Y. Lee

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 6 )   2011年6月

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

    Using data from the high-energy neutral atom (HENA) imager onboard the IMAGE satellite, we examined the relation between the SYM-H index and the ring current energy during a storm main phase. The energy range of the energetic neutral atom (ENA) flux data used here is 16-120 keV for hydrogen and &lt;180 keV for oxygen. From the data for the period 2000-2002, we selected 24 storm main phase events during which the IMAGE satellite was located at a geomagnetic latitude of &gt;= 45 degrees and a geocentric distance of &gt;= 6 R-E. According to the Dessler-Parker-Sckopke (DPS) equation, the ring current energy is expected to increase as the SYM-H index decreases. When the ENA energy flux is superimposed as a function of the SYM-H index for all 24 events, their overall correlation is negative; that is, the relation between the ENA energy flux and the SYM-H index is generally consistent with the DPS equation. However, an analysis of individual events showed only 10 events (42%) in which the ENA energy flux was negatively correlated with the SYM-H index (negative correlation events). There were 10 events showing no clear correlation between the ENA energy flux and the SYM-H index (no correlation events) and 4 events which contradicted the DPS equation (positive correlation events). In the superimposed plot, we noted that a smooth curve can be drawn for an upper limit of the data distribution, and data from the no correlation or positive correlation events create downward branches in the distribution. These observational results are not explained by the conventional DPS equation but by the "generalized" DPS equation, which includes a term representing energy stored in the stretched magnetic field. We can reasonably presume that the stretched magnetic field prevents energetic particles from being injected into the ring current. From the generalized DPS equation, we conclude that the total (kinetic and magnetic) energy stored in the stretched field and ring current loss mechanisms are important for understanding the relation between the ground magnetic field variation and ring current energy variation.

    DOI: 10.1029/2010JA015799

    Web of Science

  65. Evolution of ring current ion energy spectra during the storm recovery phase: Implication for dominant ion loss processes 査読有り

    K. Keika, P. C. Brandt, M. Nose, D. G. Mitchell

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 3 )   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  

    We examine the temporal evolution of spatially averaged energy spectra of ring current ions (27-120 keV for H+, 79-264 keV for O+) during the recovery phase of three magnetic storms. The energy spectra are derived from energetic neutral atom (ENA) imaging provided by the High Energy Neutral Atom (HENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite; ENAs generated within HENA lines of sight passing by close to the Earth are excluded in order to distinguish high-altitude emissions from low-altitude emissions. We confirm, by performing a simple model of ENA production, that the retrieved spectra are a good indication of those at 3.5 &lt; L &lt; 5. The spectral evolution during the early and rapid recovery phase of the examined intense and weak storms shows that higher-energy H+ were lost more than lower-energy H+. The loss rate of similar to 100 keV H+ is higher than or comparable to that of similar to 100 keV O+. During the early and rapid recovery of the examined moderate storm, the O+ loss rate was higher for lower energies. These results suggest that charge exchange makes a small contribution to the ring current rapid recovery. We conclude that ion precipitation through pitch angle scattering (probably due to interactions with electromagnetic ion cyclotron waves) plays a significant role in ion loss during the early and rapid recovery phase. For the late and slow recovery phase, on the other hand, the spectral evolution is consistent with that expected from charge exchange. The retrieved phase space density of &lt;60 keV H+ decreased down to around the prestorm level when Dst did not yet recover to the prestorm value, while the phase space density of &gt;60 keV H+ was higher than the prestorm level. It is likely that the contribution from &gt;60 keV H+ to the ring current intensity (and H+ pressure) increases as a storm recovers. We suggest that the ring current intensity is dominated by higher-energy (&gt;60 keV) H+ during the late recovery phase.

    DOI: 10.1029/2010JA015628

    Web of Science

  66. Modeling the superstorm in November 2003 査読有り

    Mei-Ching Fok, Thomas E. Moore, Steve P. Slinker, Joel A. Fedder, Dominique C. Delcourt, Masahito Nose, Sheng-Hsien Chen

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 1 )   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  

    The superstorm on 20-21 November 2003 was the largest geomagnetic storm in solar cycle 23 as measured by Dst, which attained a minimum value of -422 nT. We have simulated this storm to understand how particles originating from the solar wind and ionosphere get access to the magnetosphere and how the subsequent transport and energization processes contribute to the buildup of the ring current. The global electromagnetic configuration and the solar wind H+ distribution are specified by the Lyon-Fedder-Mobarry (LFM) magnetohydrodynamics model. The outflow of H+ and O+ ions from the ionosphere are also considered. Their trajectories in the magnetosphere are followed by a test-particle code. The particle distributions at the inner plasma sheet established by the LFM model and test-particle calculations are then used as boundary conditions for a ring current model. Our simulations reproduce the rapid decrease of Dst during the storm main phase and the fast initial phase of recovery. Shielding in the inner magnetosphere is established at early main phase. This shielding field lasts several hours and then breaks down at late main phase. At the peak of the storm, strong penetration of ions earthward to L shell of 1.5 is revealed in the simulation. It is surprising that O+ is significant but not the dominant species in the ring current in our calculation for this major storm. It is very likely that substorm effects are not well represented in the models and O+ energization is underestimated. Ring current simulation with O+ energy density at the boundary set comparable to Geotail observations produces excellent agreement with the observed symH. As expected in superstorms, ring current O+ is the dominant species over H+ during the main to midrecovery phase of the storm.

    DOI: 10.1029/2010JA015720

    Web of Science

  67. Pressure changes associated with substorm depolarization in the near-Earth plasma sheet (vol 116, A01299, 2011) 査読有り

    Y. Miyashita, S. Machida, A. Ieda, D. Nagata, Y. Kamide, M. Nose, K. Liou, T. Mukai, S. P. Christon, C. T. Russell, I. Shinohara, Y. 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  

    DOI: 10.1029/2010JA016389

    Web of Science

  68. Erratum: Pressure changes associated with substorm depolarization in the near-Earth plasma sheet (Journal of Geophysical Research A: Space Physics 115 (A12239) DOI: 10.1029/2010JA015608) 査読有り

    Y. Miyashita, S. MacHida, A. Ieda, D. Nagata, Y. Kamide, M. Nosé, K. Liou, T. Mukai, S.P. Christon, C.T. Russell, I. Shinohara, Y. Saito

    Journal of Geophysical Research A: 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)  

    DOI: 10.1029/2010JA016389

  69. Geomagnetic Indices 査読有り

    Michel Menvielle, Toshihiko Iyemori, Aurélie Marchaudon, Masahito Nosé

    Geomagnetic Observations and Models     頁: 183 - 228   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Michel Menvielle, Toshihiko Iyemori, Aurélie Marchaudon, Masahito Nosé, 2011, &#039;Geomagnetic Indices&#039;, &lt;i&gt;Geomagnetic Observations and Models&lt;/i&gt;, pp. 183-228

    DOI: 10.1007/978-90-481-9858-0_8

    その他リンク: http://orcid.org/0000-0002-2789-3588

  70. Magnetic local time dependence of geomagnetic disturbances contributing to the AU and AL indices 査読有り

    S. Tomita, M. Nose, T. Iyemori, H. Toh, M. Takeda, J. Matzka, G. Bjornsson, T. Saemundsson, A. Janzhura, O. Troshichev, G. Schwarz

    ANNALES GEOPHYSICAE   29 巻 ( 4 ) 頁: 673 - 678   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:COPERNICUS GESELLSCHAFT MBH  

    The Auroral Electrojet (AE) indices, which are composed of four indices (AU, AL, AE, and AO), are calculated from the geomagnetic field data obtained at 12 geomagnetic observatories that are located in geomagnetic latitude (GMLAT) of 61.7 degrees-70 degrees. The indices have been widely used to study magnetic activity in the auroral zone. In the present study, we examine magnetic local time (MLT) dependence of geomagnetic field variations contributing to the AU and AL indices. We use 1-min geomagnetic field data obtained in 2003. It is found that both AU and AL indices have two ranges of MLT (AU: 15:00-22:00 MLT, similar to 06:00 MLT; and AL: similar to 02:00 MLT, 09:00-12:00 MLT) contributing to the index during quiet periods and one MLT range (AU: 15:00-20:00 MLT, and AL: 00:00-06:00 MLT) during disturbed periods. These results are interpreted in terms of various ionospheric current systems, such as, S(q)(p), S(q), and DP2.

    DOI: 10.5194/angeo-29-673-2011

    Web of Science

    J-GLOBAL

  71. Magnetic Observatory Data and Metadata: Types and Availability 査読有り

    Sarah J. Reay, Donald C. Herzog, Sobhana Alex, Evgeny P. Kharin, Susan McLean, Masahito Nosé, Natalia A. Sergeyeva

    Geomagnetic Observations and Models     頁: 149 - 181   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Sarah J. Reay, Donald C. Herzog, Sobhana Alex, Evgeny P. Kharin, Susan McLean, Masahito Nosé, Natalia A. Sergeyeva, 2011, &#039;Magnetic Observatory Data and Metadata: Types and Availability&#039;, &lt;i&gt;Geomagnetic Observations and Models&lt;/i&gt;, pp. 149-181

    DOI: 10.1007/978-90-481-9858-0_7

    その他リンク: http://orcid.org/0000-0002-2789-3588

  72. Pressure changes associated with substorm depolarization in the near-Earth plasma sheet 査読有り

    Miyashita Y., Machida S., Ieda A., Nagata D., Kamide Y., Nose M., Liou K., Mukai T., Christon S. P., Russell C. T., Shinohara I., Saito Y.

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

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2010JA015608

    Web of Science

    Scopus

  73. Mass-dependent evolution of energetic neutral atoms energy spectra during storm time substorms: Implication for O+ nonadiabatic acceleration 査読有り

    K. Keika, P. C. Brandt, S. Ohtani, D. G. Mitchell, K. Min, M. Nose, T. Obara, H. Koshiishi, H. Matsumoto

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

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

    We examine the temporal variations of energy spectra of energetic neutral atoms (ENAs) detected by the High Energy Neutral Atom imager (HENA) onboard the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite during three substorms on 21 October 2001 and three substorms on 19 March 2002; the substorms occurred during the storm main phase. The ENA energy used in the present study ranges from 10 to 198 keV for hydrogen and from 29 to 222 keV for oxygen. We use ENA data obtained from two independent areas of a HENA image, for which HENA lines of sight pass through the inner magnetosphere (similar to-6 RE &lt; X &lt; similar to-3 R-E around the magnetic equator) and the outer magnetosphere (X &lt; similar to-6 R-E around the magnetic equator). The analyses of the selected ENA data yield the following results: (1) The oxygen ENA flux displays 20-30 min bursts during all substorms, while the hydrogen ENA flux did not increase or less significantly increased than the oxygen flux. (2) The temporal evolution of energy spectra is mass dependent for all examined substorms. (3) For two of the substorms, the oxygen flux ratio between before and after a substorm increases with increasing energy, indicating the hardening of an O+ energy spectrum. (4) The flux ratio for the inner image area is comparable to or higher than that in the outer area. The results confirm that nonadiabatic acceleration with regard to the first adiabatic invariant did occur in the near-Earth magnetotail (X &gt; -8 R-E). Although the influence of the nonadiabatic acceleration appears in the inner magnetosphere (similar to-6 R-E &lt; X &lt; similar to-3 R-E) as well as the outer magnetosphere (similar to-8 R-E &lt; X &lt; similar to-6 R-E), it is not clear from the present results whether O+ energization in the inner magnetosphere is due to nonadiabatic acceleration in the inner magnetosphere or adiabatic transport of O+ nonadiabatically accelerated in the outer magnetosphere. It is likely, for at least the two substorms, that the nonadiabatic acceleration makes a more significant contribution to O+ energization than increase of the O+ density in the plasma sheet.

    DOI: 10.1029/2010JA015889

    Web of Science

  74. Multipoint observation of fast mode waves trapped in the dayside plasmasphere 査読有り

    Kazue Takahashi, John Bonnell, Karl-Heinz Glassmeier, Vassilis Angelopoulos, Howard J. Singer, Peter J. Chi, Richard E. Denton, Yukitoshi Nishimura, Dong-Hun Lee, Masahito Nose, Wenlong Liu

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( A12 )   2010年12月

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

    Multipoint observations of a dayside Pc4 pulsation event provide evidence of fast mode waves trapped in the plasmasphere (plasmaspheric cavity mode or virtual resonance). Time History of Events and Macroscale Interactions during Substorms (THEMIS)-A, the primary source of data for the present study, was moving outward near noon and detected poloidal oscillations, characterized by the azimuthal electric field component E-y and the radial and compressional magnetic field components B-x and B-z. The structure of the plasmasphere was constructed from the mass density radial profile estimated from the frequency of toroidal standing Alfven waves observed at this spacecraft. The outer edge of the plasmapause (the maximum of the equatorial Alfven velocity V-Aeq) was located at L similar to 7, and the minimum of V-Aeq was located at L similar to 4, forming a potential well structure required for mode trapping. Relative to the ground magnetic pulsations observed in the H component at a low-latitude station (L = 1.5), the E-y component exhibited a broad amplitude maximum around L similar to 3.5 and maintained a nearly constant phase from L = 2 to L = 5. In contrast, the B-z component exhibited an amplitude minimum and switched its phase by 180 degrees at L = 3.8. This radial mode structure is consistent with theoretical models of mode trapping. Also, the E-y and B-z components oscillated +/- 90 degrees out of phase, as is expected for radially standing waves.

    DOI: 10.1029/2010JA015956

    Web of Science

  75. Mass-dependent evolution of energetic neutral atoms energy spectra during storm time substorms: Implication for O+ nonadiabatic acceleration 査読有り

    K. Keika, P. C. Brandt, S. Ohtani, D. G. Mitchell, K. Min, M. Nose, T. Obara, H. Koshiishi, H. Matsumoto

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

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

    We examine the temporal variations of energy spectra of energetic neutral atoms (ENAs) detected by the High Energy Neutral Atom imager (HENA) onboard the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite during three substorms on 21 October 2001 and three substorms on 19 March 2002; the substorms occurred during the storm main phase. The ENA energy used in the present study ranges from 10 to 198 keV for hydrogen and from 29 to 222 keV for oxygen. We use ENA data obtained from two independent areas of a HENA image, for which HENA lines of sight pass through the inner magnetosphere (similar to-6 RE &lt; X &lt; similar to-3 R-E around the magnetic equator) and the outer magnetosphere (X &lt; similar to-6 R-E around the magnetic equator). The analyses of the selected ENA data yield the following results: (1) The oxygen ENA flux displays 20-30 min bursts during all substorms, while the hydrogen ENA flux did not increase or less significantly increased than the oxygen flux. (2) The temporal evolution of energy spectra is mass dependent for all examined substorms. (3) For two of the substorms, the oxygen flux ratio between before and after a substorm increases with increasing energy, indicating the hardening of an O+ energy spectrum. (4) The flux ratio for the inner image area is comparable to or higher than that in the outer area. The results confirm that nonadiabatic acceleration with regard to the first adiabatic invariant did occur in the near-Earth magnetotail (X &gt; -8 R-E). Although the influence of the nonadiabatic acceleration appears in the inner magnetosphere (similar to-6 R-E &lt; X &lt; similar to-3 R-E) as well as the outer magnetosphere (similar to-8 R-E &lt; X &lt; similar to-6 R-E), it is not clear from the present results whether O+ energization in the inner magnetosphere is due to nonadiabatic acceleration in the inner magnetosphere or adiabatic transport of O+ nonadiabatically accelerated in the outer magnetosphere. It is likely, for at least the two substorms, that the nonadiabatic acceleration makes a more significant contribution to O+ energization than increase of the O+ density in the plasma sheet.

    DOI: 10.1029/2010JA015889

    Web of Science

  76. Magnetic field dipolarization in the deep inner magnetosphere and its role in development of O+-rich ring current 査読有り

    M. Nose, H. Koshiishi, H. Matsumoto, P. Cson Brandt, K. Keika, K. Koga, T. Goka, T. Obara

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

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

    We studied magnetic field dipolarization and associated ion acceleration in the deep inner magnetosphere, using magnetic field data obtained by the magnetometer on board the Mission Demonstration Satellite 1 (MDS-1) and the energetic neutral atom (ENA) flux data obtained by the high-energy neutral analyzer imager on board the Imager for Magnetopause-to-Aurora Global Exploration satellite. Because the MDS-1 satellite has a geosynchronous transfer orbit, we could survey magnetic field variations at L = 3.0-6.5. Analyzing data in the period from February to July 2002, we found that (1) dipolarization can be detected over a wide range of L (i.e., L = 3.5-6.5, which is far inside the geosynchronous altitude); (2) when the MDS-1 satellite was located close to auroral breakup longitude, the occurrence probability of dipolarization was about 50% just inside the geosynchronous altitude and about 16% at L = 3.5-5.0, suggesting that dipolarization in the deep inner magnetosphere is not unusual; (3) magnetic storms were developing whenever dipolarization was found at L = 3.5-5.0; (4) dipolarization was accompanied by magnetic field fluctuations having a characteristic timescale of 3-5 s, which is comparable to the local gyroperiod of O+ ions; and (5) after dipolarization, the oxygen ENA flux in the nightside ring current region was predominantly enhanced by a factor of 2-5 and stayed at an enhanced level for more than 1 h, while clear enhancement was scarcely seen in the hydrogen ENA flux. From these results, we conjectured a scenario for the generation of an O+-rich ring current, in which preexisting thermal O+ ions in the outer plasmasphere (i.e., an oxygen torus known from satellite observations) experience local and nonadiabatic acceleration by magnetic field fluctuations that accompany dipolarization in the deep inner magnetosphere (L = 3.5-5.0).

    DOI: 10.1029/2010JA015321

    Web of Science

  77. A new generation mechanism of butterfly pitch angle distributions of energetic ions: Multiple pitch angle scattering in the stretched magnetic field 査読有り

    K. Shibahara, M. Nose, T. A. Fritz, J. Niehof

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 7 )   2010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  

    A new generation mechanism of a butterfly pitch angle distribution (PAD) of energetic ions is demonstrated by a test particle simulation in the stretched magnetic field. The Polar satellite detected some events of the butterfly PADs of the energetic protons (greater than or similar to 80 keV) in the outer ring current region around midnight near the equatorial plane. They were observed at relatively disturbed time in the inner magnetosphere and the ring current appeared to be developed; that is, magnitude of the magnetic field at the Polar satellite was highly depressed and the adiabaticity of the protons were expected to be violated. To reproduce the butterfly PAD, we perform a test particle simulation in which the first adiabatic invariant mu can be changed. When the radius of the field line becomes almost comparable to the Larmor radius of a proton, it suffers significant scattering of pitch angle (a) due to change of mu. This mu-scattering process causes reform of the PADs. Owing to cumulative mu-scattering, the flux of the protons ends to have a peak at alpha similar to 40 degrees (or 140 degrees) and collapses at alpha similar to 0 degrees (or 180 degrees) and 90 degrees, which is a butterfly PAD. The reproduced PAD resembles the butterfly PADs observed by the Polar satellite. We suggest that the nonadiabatic effect is important for not only the generation mechanisms of the butterfly PAD but also the development of the storm-time ring current.

    DOI: 10.1029/2010JA015281

    Web of Science

  78. Excitation mechanism of low-latitude Pi2 pulsations: Cavity mode resonance or BBF-driven process? 査読有り

    M. Nosé

    Journal of Geophysical Research: Space Physics   115 巻 ( 7 )   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  

    There are two schools of thought regarding the excitation mechanism of low-latitude Pi2 pulsations. One is the cavity mode resonance, which is established by fast mode waves that are emitted at substorm onset and form the standing oscillation within the plasmasphere. The other is the bursty bulk flow (BBF)-driven process, in which periodical BBFs traveling from the magnetotail cause pressure pulses in the inner magnetosphere, generating Pi2 pulsations. This study intends to examine which of these two excitation mechanisms is more plausible. A working assumption is that in the case of the cavity mode resonance the wave period of Pi2 pulsations depends on the size and the plasma mass density of the plasmasphere, while in the case of the BBF-driven process the wave period is controlled by the BBF period and is independent of the plasmaspheric parameters. We investigated long-term variation in wave period of Pi2 pulsations observed at the Kakioka observatory for the period from March 1983 to October 2009. Multiple correlation analysis revealed that the Pi2 period is negatively correlated with the ∑Kp index and positively correlated with ion mass in the near-Earth plasma sheet or the F10.7 index. The ∑Kp index is considered as a proxy for the size of the plasmasphere, and the plasma sheet ion mass or the F10.7 index can be considered as a proxy for the mass density of the plasmasphere, indicating that the Pi2 period is proportional to both the size and mass density of the plasmasphere. This result strongly supports the plasmaspheric cavity mode resonance as an excitation mechanism of low-latitude Pi2 pulsations. Copyright 2010 by the American Geophysical Union.

    DOI: 10.1029/2009JA015205

    Scopus

  79. Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere and in the plasma sheet 査読有り

    M. Nose, S. Taguchi, S. P. Christon, M. R. Collier, T. E. Moore, C. W. Carlson, J. P. McFadden

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   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:AMER GEOPHYSICAL UNION  

    We investigate variations of ion flux over the ionosphere and in the plasma sheet when storm time substorms are initiated, using simultaneous observations of neutral atoms in the energy range of up to a few keV measured by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) satellite, outflowing ion flux of &lt;1 keV measured by the ion electrostatic analyzer (IESA) on board the Fast Auroral SnapshoT (FAST) satellite, and energetic (9-210 keV/e) ion flux measured by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite. We examined three storm intervals during which the IMAGE or FAST satellite was in a suitable location to observe ionospheric ion outflow and the Geotail satellite was in the plasma sheet on the nightside. The neutral atom flux observed by IMAGE/LENA in the first interval and outflowing ion flux observed by FAST/IESA in the second and third intervals indicate that storm time substorms can cause increases of low-energy ion flux over the ionosphere by a factor of 3-50 with time delay of less than several minutes. In the plasma sheet, the flux ratio of O+/H+ is rapidly enhanced at the storm time substorms and then increased gradually or stayed at a constant level in a time scale of similar to 1 h, suggesting a mass-dependent acceleration of ions at local dipolarization and a subsequent additional supply of O+ ions to the plasma sheet which have been extracted from the ionosphere at the substorms. These coordinated observations revealed that substorms have both an immediate effect and a delayed effect (i.e., two-step effect) on the ion composition in the plasma sheet.

    DOI: 10.1029/2009JA014048

    Web of Science

  80. The role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization 査読有り

    Y. Ono, M. Nose, S. P. Christon, A. T. Y. Lui

    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:AMER GEOPHYSICAL UNION  

    We statistically examine changes in the composition of two different ion species, proton and oxygen ions, in the near-Earth plasma sheet (X = -16 R(E) similar to -6 R(E)) during substorm-associated dipolarization. We use 10 years of energetic (9-212 keV/e) ion data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particles and ion composition (EPIC) instrument on board the Geotail spacecraft. The results are as follows: (1) Although the percentage increase in the energy density of O(+) ions before and after a dipolarization exceeds that of H(+) ions in the low-energy range (9-36 keV/e), this property is not evident in the high-energy range (56-212 keV/e); (2) the energy spectrum of H(+) and that of O(+) become harder after dipolarization in almost all events; and (3) in some events the energy spectrum of O+ becomes harder than that of H(+) as reported by previous studies, and, importantly, in other events, the spectrum of H(+) becomes harder than that of O(+). In order to investigate what mechanism causes these observational results, we focus on magnetic field fluctuations during dipolarization. It is found that the increase of the spectrum slope is positively correlated with the power of waves whose frequencies are close to the gyrofrequency of H(+) or O(+), respectively (the correlation coefficient is 0.48 for H(+) and 0.68 for O(+)). In conclusion, ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies.

    DOI: 10.1029/2008JA013918

    Web of Science

  81. Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere and in the plasma sheet 査読有り

    M. Nose, S. Taguchi, S. P. Christon, M. R. Collier, T. E. Moore, C. W. Carlson, J. P. McFadden

    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:AMER GEOPHYSICAL UNION  

    We investigate variations of ion flux over the ionosphere and in the plasma sheet when storm time substorms are initiated, using simultaneous observations of neutral atoms in the energy range of up to a few keV measured by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) satellite, outflowing ion flux of &lt;1 keV measured by the ion electrostatic analyzer (IESA) on board the Fast Auroral SnapshoT (FAST) satellite, and energetic (9-210 keV/e) ion flux measured by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite. We examined three storm intervals during which the IMAGE or FAST satellite was in a suitable location to observe ionospheric ion outflow and the Geotail satellite was in the plasma sheet on the nightside. The neutral atom flux observed by IMAGE/LENA in the first interval and outflowing ion flux observed by FAST/IESA in the second and third intervals indicate that storm time substorms can cause increases of low-energy ion flux over the ionosphere by a factor of 3-50 with time delay of less than several minutes. In the plasma sheet, the flux ratio of O+/H+ is rapidly enhanced at the storm time substorms and then increased gradually or stayed at a constant level in a time scale of similar to 1 h, suggesting a mass-dependent acceleration of ions at local dipolarization and a subsequent additional supply of O+ ions to the plasma sheet which have been extracted from the ionosphere at the substorms. These coordinated observations revealed that substorms have both an immediate effect and a delayed effect (i.e., two-step effect) on the ion composition in the plasma sheet.

    DOI: 10.1029/2009JA014048

    Web of Science

  82. Acoustic resonance between ground and thermosphere 査読有り

    M. Matsumura, T. Iyemori, Y. Tanaka, D. Han, M. Nose, M. Utsugi, N. Oshiman, H. Shinagawa, Y. Odagi, Y. Tabata

    Data Science Journal   8 巻   頁: S68 - S77   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:Ubiquity Press Ltd  

    Ultra-low frequency acoustic waves called "acoustic gravity waves" or "infrasounds" are theoretically expected to resonate between the ground and the thermosphere. This resonance is a very important phenomenon causing the coupling of the solid Earth, neutral atmosphere, and ionospheric plasma. This acoustic resonance, however, has not been confirmed by direct observations. In this study, atmospheric perturbations on the ground and ionospheric disturbances were observed and compared with each other to confirm the existence of resonance. Atmospheric perturbations were observed with a barometer, and ionospheric disturbances were observed using the HF Doppler method. An end point of resonance is in the ionosphere, where conductivity is high and the dynamo effect occurs. Thus, geomagnetic observation is also useful, so the geomagnetic data were compared with other data. Power spectral density was calculated and averaged for each month. Peaks appeared at the theoretically expected resonance frequencies in the pressure and HF Doppler data. The frequencies of the peaks varied with the seasons. This is probably because the vertical temperature profile of the atmosphere varies with the seasons, as does the reflection height of infrasounds. These results indicate that acoustic resonance occurs frequently.

    DOI: 10.2481/dsj.8.S68

    Scopus

  83. A state-of-the-art picture of substorm-associated evolution of the near-Earth magnetotail obtained from superposed epoch analysis 査読有り

    Miyashita Y., Machida S., Kamide Y., Nagata D., Liou K., Fujimoto M., Ieda A., Saito M. H., Russell C. T., Christon S. P., Nose M., Frey H. U., Shinohara I., Mukai T., Saito Y., Hayakawa H.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻 ( 1 )   2009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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2008JA013225

    Web of Science

    Scopus

  84. Statistical visualization of the earth's magnetotail based on geotail data and the implied substorm model 査読有り

    Machida S.

    Annales Geophysicae   27 巻 ( 3 ) 頁: 1035 - 1046   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:Annales Geophysicae  

    DOI: 10.5194/angeo-27-1035-2009

    Web of Science

    Scopus

  85. Geotail observations of plasma sheet ion composition over 16 years: On variations of average plasma ion mass and O<sup>+</sup> triggering substorm model

    Nosé M.

    Journal of Geophysical Research: Space Physics   114 巻 ( 7 )   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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2009JA014203

    Web of Science

    Scopus

  86. Dawnside particle injection caused by sudden enhancement of solar wind dynamic pressure 査読有り

    D. -S. Han, H. -G. Yang, M. Nose, D. -H. Huang, Z. -T. Chen, H. -Q. Hu

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   70 巻 ( 16 ) 頁: 1995 - 1999   2008年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Here we present the first evidence for particle injection in the dawn-side equatorial plane caused by a sudden enhancement of the solar wind dynamic pressure (SEP(dyn))The observational results demonstrate that the SEP(dyn) caused two effects: (1) instantaneous particle energization in the dayside, and (2) particle injection in the dawn side at approximately 7 min later. The former effect has been suggested to be energization of the preexisting particles by the sudden compression of the magnetosphere. We argue that the latter effect was due to acceleration of relatively hot ions in the dawn-side plasma sheet by a bipolar electric field caused by the SEP(dyn). (C) 2008 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jastp.2008.07.019

    Web of Science

    J-GLOBAL

  87. Determination of the substorm initiation region from a major conjunction interval of THEMIS satellites 査読有り

    A. T. Y. Lui, V. Angelopoulos, O. LeContel, H. Frey, E. Donovan, D. G. Sibeck, W. Liu, H. U. Auster, D. Larson, X. Li, M. Nose, M. O. Fillingim

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

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

    We investigate in detail the time history of substorm disturbances in the magnetotail observed during a major tail conjunction of Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites on 29 January 2008, 0700-0900 UT. During this interval, all THEMIS satellites were closely aligned along the tail axis near midnight and were bracketed in local time by GOES 11 and 12. The radial distance covered ranges from the geosynchronous altitude to similar to 30 R-E in the tail. This interval consists of three activations detected by the THEMIS satellites with good ground all-sky-camera observations of auroral activity. The first activation is a small substorm with spatially limited disturbance in the tail. The onset arc was equatorward of an undisturbed arc. The second activation is a moderate size substorm with the onset arc also being equatorward of an undisturbed arc. The third activation is an intensification of the substorm with its onset indicated by the second activation. The active auroral arc for this intensification was near the poleward boundary of the auroral oval. Analysis of these observations indicates that the first activation is a small substorm initiated in the near-Earth plasma sheet and does not involve magnetic reconnection of open magnetic field lines. Magnetic reconnection on closed field lines can be ruled out for this substorm because it cannot generate the observed high-speed plasma flow. The second and third activations are part of a moderate size substorm initiated also in the near-Earth plasma sheet, with a subsequent substorm intensification involving activity initiated tailward of similar to 30 R-E. Overall, the time history of substorm activity for these two substorms is consistent with the near-Earth initiation model.

    DOI: 10.1029/2008JA013424

    Web of Science

  88. Longitudinal association between magnetotail reconnection and auroral breakup based on Geotail and Polar observations 査読有り

    Ieda A., Fairfield D. H., Slavin J. A., Liou K., Meng C. -I., Machida S., Miyashita Y., Mukai T., Saito Y., Nose M., Shue J. -H., Parks G. K., Fillingim M. O.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A8 )   2008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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2008JA013127

    Web of Science

    Scopus

  89. Statistical analysis of Pi2 pulsations inside and outside the plasmasphere observed by the polar orbiting DE-1 satellite 査読有り

    M. Teramoto, M. Nose, P. R. Sutcliffe

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A7 )   2008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  

    [1] We have statistically analyzed Pi2 pulsations, using the 6-second magnetic field data acquired by the polar orbiting DE-1 satellite ( a perigee of about 500 km altitude and an apogee of about 3.6 RE altitude). From February 1983 to January 1991, 746 events were found in the H component of the geomagnetic field data from Kakioka or Hermanus, which were located near midnight at substorm onsets determined with the AL index. Out of these 746 events, 91 events had high coherence (&gt; 0.6) between DE-1 and ground stations. We examined the spatial distributions of the occurrence probability and the L dependence of the power ratio to the ground and phase difference. The following observational results are obtained: ( 1) There are many high- coherence events in the compressional component at high latitude as well as at low latitude on the nightside; ( 2) In the compressional component, the power ratio of DE-1 to ground stations has a weak peak around L similar to 5 on the nigthside and flankside; and ( 3) the phase difference between DE-1 and ground stations is changed by similar to 180 degrees around L similar to 5 on the nightside and flankside. Some high- coherence events were found in the compressional component in the polar region. We concluded Pi2 pulsations might be excited by plasmaspheric virtual resonance (PVR) mode, in which compressional waves are produced inside the plasmasphere and oscillate the ambient magnetic field at high latitude.

    DOI: 10.1029/2007JA012740

    Web of Science

  90. Storm phase dependence of ion outflow: Statistical signatures obtained by IMAGE/LENA 査読有り

    T. Kunori, M. Nose, S. Taguchi, K. Hosokawa, M. R. Collier, T. E. Moore

    GEOPHYSICAL RESEARCH LETTERS   34 巻 ( 18 )   2007年9月

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

    The low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) spacecraft can observe energetic neutral atoms (ENA) of 10 eV to a few keV generated by upflowing ions through charge exchange with the Earth's exosphere. Using IMAGE/LENA data, we statistically analyzed behaviors of the ion outflow in the main and recovery phases of the magnetic storms from June 2000 to December 2001. Results show that during the main phase, most of ENA emissions from the Earth's direction are accompanied by the solar wind dynamic pressure (P-dy) enhancements. For the recovery phase, there are no such tendencies. Instead, the ENA flux shows large values at the beginning of the recovery phase, and then decreases with the storm recovery. These results suggest that the dominant mechanism responsible for the ion outflow during the magnetic storms can be totally different between the two phases.

    DOI: 10.1029/2007GL029877

    Web of Science

  91. Coupling of perturbations in the solar wind density to global Pi3 pulsations: A case study 査読有り

    D.-S. Han, H.-G. Yang, Z.-T. Chen, T. Araki, M. W. Dunlop, M. Nose, T. Iyemori, Q. Li, Y.-F. Gao, K. Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A5 )   2007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  

    [1] A typical Pi3 pulsation is examined by magnetic field measurements from multiple satellites and ground stations. Low-latitude ground observations with a wide longitudinal span indicate that the amplitude of the Pi3 pulsation peaks on the dayside and is gradually decreasing toward the nightside. This effect and the fact that the wave phase on the dayside leads that on the nightside, imply that the source of the Pi3 lies on the dayside. Variations in solar wind dynamic pressure observed by the GEOTAIL satellite (just outside of the magnetosphere) are highly correlated with these ground magnetic field variations. We argue in this case that the global Pi3 pulsation is directly driven by impulsive variations in the solar wind dynamic pressure. The Pi3 pulsation observed along the latitudinal magnetometer chain at 0930LT shows significant equatorial enhancement and additional observations along a latitudinal chain at 1630LT show that the phase of the Pi3 pulsation at high latitudes lags behind that at low latitudes. The low-altitude polar orbiting satellite Oersted also observed this pulsation in the dayside inner magnetosphere. The B-parallel to (northward) component at Oersted is strictly out of phase with the X component observed at the dip equator below the spacecraft path, which indicates that the Pi3 pulsation at the dip equator is caused by oscillation of an ionospheric current. We propose that the Pi3 pulsations at different latitudes are generated by different mechanisms.

    DOI: 10.1029/2006JA011675

    Web of Science

  92. Polarization analysis of a Pi2 pulsation using continuous wavelet transform 査読有り

    M. Kulesh, M. Nose, A. Holschneider, K. Yumoto

    EARTH PLANETS AND SPACE   59 巻 ( 8 ) 頁: 961 - 970   2007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  

    In this contribution, we extend a series of previous works focused on an investigation of signal's polarization attributes using the continuous wavelet transform, where we proposed a method to map instantaneous polarization attributes of multicomponent signals in the wavelet domain and explicitly relate these attributes with the wavelet transform coefficients of the analyzed signal. In this work, we applied our polarization method to an examination of characteristics of Pi2 pulsations. We have shown some merits of the use of the continuous wavelet transform for the Pi2 pulsations' analysis. First, we used our polarization method for the geomagnetic field data from the MSR, KAK, GUA, SMA, BLM and LAQ observatories and showed some correlations between the polarization parameters of pulsation and the station's position (nightside or dayside). Secondly, we considered the signal's north components of a pair of stations and demonstrated a time-frequency variations of the phase difference between two stations during the pulsation.

    DOI: 10.1186/BF03352035

    Web of Science

    J-GLOBAL

  93. Contribution of charge exchange loss to the storm time ring current decay: IMAGE/HENA observations 査読有り

    K. Keika, M. Nose, P. C. Brandt, S. Ohtani, D. G. Mitchell, E. C. Roelof

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A11 )   2006年11月

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

    The present study addresses the contribution of charge exchange loss of the ring current ions to the decay of the storm time ring current, based on measurements of energetic neutral atoms (ENAs) made by the High Energy Neutral Atom (HENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) satellite. The energy range of ENA fluxes examined in the present study is from 27 to 119 keV for hydrogen and from 79 to 264 keV for oxygen. This is the first statistical estimate of the charge exchange contribution made with dedicated measurements of both neutral hydrogen and oxygen. We estimate charge exchange energy losses of the ring current ions, employing two independent methods. The decay rate of the ring current is derived from the temporal variations of the Dst index. Our estimates show that the rate of the charge exchange energy losses is comparable to the ring current decay rate for the intervals of the slow decay, while the loss rate is much smaller than the decay rate in the rapid decay phase in particular for the early stage of a storm recovery. The logarithm of the energy loss rate is well correlated with the simultaneous Dst index, increasing as Dst decreases. Utilizing the high correlations, we simulate a Dst recovery due to charge exchange loss alone. Pressure-corrected Dst (Dst(0)) recoveries derived from measured Dst cannot be reproduced by charge exchange loss alone. We conclude that the charge exchange loss is not primarily responsible for the rapid decay of the storm time ring current.

    DOI: 10.1029/2006JA011789

    Web of Science

  94. Realistic magnetospheric density model for 29 August 2000 査読有り

    RE Denton, J Goldsten, DH Lee, RA King, ZC Dent, DL Gallagher, D Berube, K Takahashi, M Nose, D Milling, F Honary

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   68 巻 ( 6 ) 頁: 615 - 628   2006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:PERGAMON-ELSEVIER SCIENCE LTD  

    Using a two dimensional image of the Earth's plasmasphere taken by the Extreme Ultraviolet Imager (EUV) on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, in-situ electron density measurements from the IMAGE Radio Plasma Imager (RPI) instrument, measurements of magnetospheric mass density inferred from field line resonant frequencies measured by magnetometers on the Earth's surface, and a model for the density field aligned variation, we construct a computer model for the magnetospheric density on 29 August 2000 at 1519 UT. The purposes of this study are to demonstrate how a density model can be constructed using multiple data sources, to document this particular model, which is being used in studies of ultra low frequency Pi-2 oscillations and plasmaspheric cavity modes, to describe some of the problems involved with EUV density inversion, and to demonstrate some features of the plasmaspheric density, particularly in the region of the dusk plasmatrough and plume. (c) 2005 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jastp.2005.11.009

    Web of Science

    J-GLOBAL

  95. ERG - A small-satellite mission to investigate the dynamics of the inner magnetosphere

    Shlokawa K., Seki K., Miyoshi Y., Leda A., Ono T., Iizima M., Nagatsuma T., Obara T., Takashima T., Asamura K., Kasaba Y., Matsuoka A., Saito Y., Saito H., Hirahara M., Tonegawa Y., Toyama F., Tanaka M., Nose M., Kasahara Y., Yumoto K., Kawano H., Yoshikawa A., Ebihara Y., Yukimatsu A., Sato N., Watanabe S.

    ADVANCES IN SPACE RESEARCH   38 巻 ( 8 ) 頁: 1861 - 1869   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.asr.2005.05.089

    Web of Science

    Scopus

  96. 'Cosmic-ray-mediated' interplanetary shocks in 1994 and 2003 査読有り

    T. Terasawa, M. Oka, K. Nakata, K. Keika, M. Nose, R. W. McEntire, Y. Saito, T. Mukai

    PARTICLE ACCELERATION, SPACE PLASMA PHYSICS, SOLAR RADIATION AND THE EARTH'S ATMOSPHERE AND CLIMATE   37 巻 ( 8 ) 頁: 1408 - 1412   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE LTD  

    Shock accelerated nonthermal particles are thought to contribute to modify the shock structure. Here we present two such cases at two strong interplanetary shocks in 1994 and 2003, and try to see how the nonlinear feature depend on the shock parameters, such as Mach number and shock angle. (c) 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.asr.2006.03.012

    Web of Science

  97. Longitudinal dependence of characteristics of low-latitude Pi2 pulsations observed at Kakioka and Hermanus 査読有り

    M Nose, K Liou, PR Sutcliffe

    EARTH PLANETS AND SPACE   58 巻 ( 6 ) 頁: 775 - 783   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    We statistically investigated longitudinal dependence of characteristics of low-latitude Pi2 pulsations to find the longitudinal structure of the plasmaspheric cavity mode. We used the geomagnetic field data from two ground stations, Kakioka (27.2 degrees geomagnetic latitude, 208.5 degrees geomagnetic longitude) and Hermanus (-33.9 degrees geomagnetic latitude, 82.2 degrees geomagnetic longitude), and auroral image data acquired by the ultraviolet imager onboard the Polar satellite for the period of December 4, 1996 to March 3, 1997. Our findings include the following: (1) Pi2 amplitude is the largest around the magnetic local time of the auroral breakup site and decreases away from it; (2) when a nightside Pi2 pulsation has large amplitude, a dayside Pi2 pulsation can be observed with a similar waveform; (3) Pi2 pulsations generally have no clear phase differences (mean phase difference of 3.3 degrees) between Kakioka and Hermanus, except for some events; and (4) the phase difference is independent on Delta MLT (difference of magnetic local time between a station and the auroral breakup). These observations suggest that the plasmaspheric cavity mode can be excited globally with a very small value of the azimuthal wave number (m approximate to 0).

    DOI: 10.1186/BF03351981

    Web of Science

    J-GLOBAL

  98. Source of Pc4 pulsations observed on the nightside 査読有り

    K Takahashi, K Liou, K Yumoto, K Kitamura, M Nose, F Honary

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A12 )   2005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  

    [1] We have studied magnetic pulsations in the 5- to 20-mHz (Pc4) band observed on 7 January 1997 from similar to 1400 UT to similar to 1600 UT at ground stations located on the nightside. At low latitudes ( L &lt; 2) the spectral content of the pulsations did not differ much from the Pi2 pulsations that were observed adjacent to the above interval. However, during the Pc4 event the auroral luminosity measured by the Ultra Violet Imager instrument on the Polar spacecraft was steadily declining toward a very low level. Also, the Geotail spacecraft, located in the plasmasheet at a geocentric distance of similar to 30 R-E did not detect strong plasma flows. Looking for clues of possible dayside sources for the pulsations, we find that the interplanetary magnetic field measured by the IMP-8 spacecraft made a small (&lt; 30 degrees) angle with the Sun-Earth axis. This condition is favorable for generation of ultra-low-frequency (ULF) waves in the region upstream of the bow shock, and it is known that the upstream waves are a major source of Pc4 pulsations observed on the dayside. Pointing to a common upstream energy source, strong low-latitude Pc4 pulsations were observed on the dayside during the period of the nightside Pc4 pulsations. However, the spectrum of the upstream magnetic field oscillations at IMP-8 was characterized by broadband power below 20 mHz instead of a strong peak at the frequency of the observed ground Pc4 pulsations. Plasmaspheric cavity mode resonance may have played a role in filtering the Pc4 pulsations from the broadband input to the magnetosphere.

    DOI: 10.1029/2005JA011093

    Web of Science

  99. Geomagnetic pulsations caused by the Sumatra earthquake on December 26, 2004 査読有り

    T Iyemori, M Nose, DS Han, YF Gao, M Hashizume, N Choosakul, H Shinagawa, Y Tanaka, M Utsugi, A Saito, H McCreadie, Y Odagi, FX Yang

    GEOPHYSICAL RESEARCH LETTERS   32 巻 ( 20 ) 頁: 1 - 4   2005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  

    A long period Pc5 pulsation was observed at Phimai in Thailand, shortly after the origin time of the Sumatra earthquake on December 26, 2004. The localized nature and the period of oscillations suggest that the long period magnetic pulsation was generated by dynamo action in the lower ionosphere, set up by an atmospheric pressure pulse which propagated vertically as an acoustic wave when the ocean floor suddenly moved vertically. It is speculated that a Pc3 type pulsation observed at Tong Hai in China, 10 degrees north of Phimai in latitude, was the result of magnetic field line resonance with a magnetosonic wave generated from the electric and magnetic fields of the dynamo current caused by the Earthquake.

    DOI: 10.1029/2005GL024083

    Web of Science

  100. Geotail observations of signatures in the near-Earth magnetotail for the extremely intense substorms of the 30 October 2003 storm 査読有り

    Miyashita Y, Miyoshi Y, Matsumoto Y, Ieda A, Kamide Y, Nose M, Machida S, Hayakawa H, McEntire RW, Christon SP, Evans DS, Troshichev OA

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A9 )   2005年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2005JA011070

    Web of Science

    Scopus

  101. Outflow of energetic ions from the magnetosphere and its contribution to the decay of the storm time ring current 査読有り

    K Keika, M Nose, S Ohtani, K Takahashi, SP Christon, RW McEntire

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A9 )   2005年9月

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

    [1] We statistically and quantitatively examine the outflow of energetic ions from the magnetosphere during magnetic storms. We also evaluate the contribution of the outflow to the decay of the ring current. We use energetic ion ( 9 - 210 keV) data obtained by the energetic particle and ion composition ( EPIC) instrument and magnetic field data obtained by the magnetic field measurements (MGF) system, both on board the Geotail spacecraft. The outflowing energy flux, that is, the energy flux lost by ring current ions flowing through the magnetopause, is defined as the energy flux normal to the magnetopause and is calculated based on measurements made adjacent to the earthward side of the low-latitude boundary layer. Our statistics show that the outflowing energy flux is about 10(5) - 10(8) keV/(cm(2) s) during both the main phase and the recovery phase. It is higher on the afternoonside than on the morningside. It is better correlated with the square root of the dynamic pressure of the solar wind than the electric field of the solar wind, which is a proxy for the strength of the convection electric field. The contribution of the outflow to the rapid decay of the ring current is estimated to be at least 23% and could be much higher than 23% for the 23 September 2001 storm, based on an underestimated leakage area which is determined from magnetic field measurements. We suggest that the drift governing the ion outflow mainly is the del B drift which has a radial component that arises from a day-night gradient of the magnetic field in the magnetosphere caused by the solar wind compression. We conclude that the ion outflow contributes significantly to the rapid decay of the ring current, even in the case of a sudden northward turning of the interplanetary magnetic field which causes a sudden decrease in the convection electric field.

    DOI: 10.1029/2004JA010970

    Web of Science

  102. Overwhelming O+ contribution to the plasma sheet energy density during the October 2003 superstorm: Geotail/EPIC and IMAGE/LENA observations 査読有り

    M Nose, S Taguchi, K Hosokawa, SP Christon, RW McEntire, TE Moore, MR Collier

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A9 )   2005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  

    [1] We studied dynamics of O+ ions during the superstorm that occurred on 29 - 31 October 2003, using energetic (9 - 210 keV/e) ion flux data obtained by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite and neutral atom data in the energy range of 10 eV to a few keV acquired by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite. Since the low-energy neutral atoms are created from the outflowing ionospheric ions by the charge exchange process, we could examine variations of ionospheric ion outflow with the IMAGE/LENA data. In the near-Earth plasma sheet of X-GSM similar to - 6 R-E to - 8.5 R-E, we found that the H+ energy density showed no distinctive differences between the superstorm and quiet intervals ( 1 - 10 keV cm(-3)), while the O+ energy density increased from 0.05 - 3 keV cm(-3) during the quiet intervals to similar to 100 keV cm(-3) during the superstorm. The O+/ H+ energy density ratio reached 10 - 20 near the storm maximum, which is the largest ratio in the near-Earth plasma sheet ever observed by Geotail, indicating more than 90% of O+ in the total energy density. We argued that such extreme increase of the O+/ H+ energy density ratio during the October 2003 superstorm was due to mass-dependent acceleration of ions by storm-time substorms as well as an additional supply of O+ ions from the ionosphere to the plasma sheet. We compared the ion composition between the ring current and the near-Earth plasma sheet reported by previous studies and found that they are rather similar. On the basis of the similarity, we estimated that the ring current had the O+/ H+ energy density ratio as large as 10 - 20 for the October 2003 superstorm.

    DOI: 10.1029/2004JA010930

    Web of Science

  103. Storm-substorm relationship: Variations of the hydrogen and oxygen energetic neutral atom intensities during storm-time substorms 査読有り

    S Ohtani, PC Brandt, DG Mitchell, H Singer, M Nose, GD Reeves, SB Mende

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A7 )   2005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 present study observationally addresses the role of the magnetospheric substorm in the storm-time ring current intensification. The intensity of energetic neutral atom (ENA) emission, which is measured by the high-energy neutral atom (HENA) imager onboard the IMAGE satellite, is carefully used as a guide for inferring the change of the ring current intensity. First, a storm event of August 2000 is examined in detail with a focus on a substorm that occurred at the start of the storm recovery phase (as defined by Sym-H). During the expansion phase of this substorm, the Sym-H index recovered ( increased) as the geosynchronous magnetic field dipolarized. At the same time the low-energy (27-60 keV) hydrogen, high-energy (60-119 keV) hydrogen, and total oxygen(&lt;160 keV for this event) ENA intensities increased, suggesting that the ring current intensified. The apparent recovery of Sym-H can therefore be attributed to the reduction of the tail current rather than the decay of the ring current. The substorm-related change of the ENA intensity is examined statistically by conducting a superposed epoch analysis, for which the onset of geosynchronous dipolarization is adopted as a reference time. The result reveals that the ENA intensity tends to decrease before substorm onsets and to increase after onsets, and so does the Sym-H index although its pre-onset decrease is less clear than the post-onset increase. It is therefore suggested that in the course of substorms, the change of the ring current intensity is opposite to what is expected from the change of the Sym-H index. The decay and intensification of the ring current can be attributed to substorm-related changes of the near-Earth magnetic field and convection. Another important result is that the response of the ENA intensity to substorms strongly depends on species and energy range. The variation of the low-energy hydrogen ENA intensity is not clearly organized by the substorm onset, and its relative change is less than 10%. The high-energy hydrogen intensity decreases by about 20% during the growth phase and then recovers to the initial level leaving no significant net increase. In contrast, the increase in the oxygen ENA intensity during the expansion phase overcompensates for the preceding reduction, resulting in a net increase of 20%. The net enhancement of the oxygen ENA intensity suggests the importance of non-adiabatic acceleration associated with near-Earth dipolarization. The timescale of dipolarization is comparable to the oxygen gyroperiod, and therefore the oxygen ions may be accelerated preferably by the associated inductive electric field. It is inferred that the substorm-related energization of the oxygen ions makes an important contribution to the storm-time ring current intensification.

    DOI: 10.1029/2004JA010954

    Web of Science

  104. Comparison of energetic ion composition between ring current and plasma sheet 査読有り

    M Nose, RW McEntire, SP Christon

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation   16 巻 ( C ) 頁: 198 - 202   2005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:ELSEVIER SCIENCE BV  

    We calculated the energy density of H+, He+, and O+ ions in the plasma sheet during the development of a magnetic storm, using energetic (9-210 keV) particle flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. We found that the energy density ratio of O+/H+ stayed at similar to 0.1 before storms, but increased as storms developed, reaching 0.5-1.0 at a peak of storms. The energy density ratio of He+/H+ was rather constant at 0.01-0.02. These results are comparable with those in the outer ring current reported by the previous studies. This implies that the ions of ionospheric origin (O+ and He+) are transported to the ring current through the plasma sheet.

    DOI: 10.1016/S0964-2749(05)80031-9

    Web of Science

  105. Influence of solar wind on source of ring current plasma 査読有り

    M Nose, RW McEntire, SP Christon

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation   16 巻 ( C ) 頁: 48 - 53   2005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:ELSEVIER SCIENCE BV  

    In the present study we aim to derive empirical equations relating source plasma of the ring current to the solar wind. We used the energy spectra at energies of 9-135 keV obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. The plasma parameters (i.e., number density and temperature) of H+, O+, and He were estimated by fitting the K-distribution function to the energy spectra in the region of a geocentric distance of 8.5-10.5 RE and magnetic local time of 2200-0200 hour. The results showed that the H+ number density in the plasma sheet correlated with the solar wind density, while the O+ and He+ number density had no correlation with the solar wind parameters. Thus the origin of H+ ions in the plasma sheet is thought to be the solar wind. O+ and He+ ions in the plasma sheet are expected to have different origin from the solar wind. It was also found that the temperature of H+, O+ and He+ has a good correlation with the solar wind velocity and that gradients of the derived empirical equations can be ordered by ion mass. This implies that ions are accelerated in a mass-dependent way.

    DOI: 10.1016/S0964-2749(05)80009-5

    Web of Science

  106. Geomagnetic activity dependence of occurrence probability and spatial distribution of upstream events 査読有り

    K Keika, M Nose, SP Christon, RW McEntire

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation   16 巻 ( C ) 頁: 297 - 300   2005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:ELSEVIER SCIENCE BV  

    We investigated upstream events observed by the ion composition system (ICS) sensor of the energetic particles and ion composition (EPIC) instrument on board the Geotail spacecraft. We examined how occurrence probability and spatial distribution of upstream events depend on the geomagnetic activity. The results showed that the upstream events were observed more frequently in the dawn side during intense geomagnetic activity in particular. We also analyzed carbon-nitrogen-oxygen ions during the upstream events. From the above results we discuss origin of the upstream energetic ions.

    DOI: 10.1016/S0964-2749(05)80045-9

    Web of Science

  107. Nosé, M., K. Takahashi, S. Ohtani, S. P. Christon, and R. W. McEntire, Dynamics of ions of ionospheric origin during magnetic storms: Their acceleration mechanism and transport path to ring current, in The Inner Magnetosphere: Physics and Modeling, Geophy 査読有り

    能勢 正仁

    AGU, Washington, D. C.,pp. 61-71     2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  108. Acceleration sites of energetic ions upstream of the Earth's bow shock and in the magnetosheath: Statistical study on charge states of heavy ions 査読有り

    K Keika, M Nose, SP Christon, RW McEntire

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   109 巻 ( A11 )   2004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  

    [1] In order to identify acceleration sites of energetic ions upstream of the Earth's bow shock and in the dayside magnetosheath, we investigated energetic ion events observed by the Energetic Particles and Ion Composition ( EPIC) instrument on board the Geotail spacecraft from 1995 to 2001. Energetic ion data obtained by the Ion Composition System ( ICS) sensor were used to select " events,'' that is, intervals when the 77 - 107 keV ion flux increased by more than two orders of magnitude within 10 min, and examine their spatial distribution and its geomagnetic activity dependence. Heavy ions with energy range of 9 - 210 keV/ e detected by the Suprathermal Ion Composition Spectrometer ( STICS) sensor were chosen to calculate the percentage of low- charge- state heavy ions ( P-LCS = ( O+ + N+)/( O+ + N+ + O6+ + O7+)) in each event, and the events were classified into three groups: high- charge- state ( HCS) events ( P-LCS less than or equal to 25%), intermediate ( IM) events ( 25% &lt; P-LCS &lt; 75%), and low- charge- state ( LCS) events ( P-LCS greater than or equal to 75%). The HCS and LCS events occurred at almost the same rate in geomagnetically quiet conditions ( SYM- H greater than or equal to 0 nT), while the LCS events were observed more frequently than the HCS events in geomagnetically disturbed conditions ( SYM- H less than or equal to - 30 nT). The percentage of the IM and LCS events summed was higher in disturbed conditions than in quiet conditions. The HCS and LCS events were frequently observed in the dawnside upstream region and in the duskside magnetosheath, respectively. The IM events occurred both in the dawnside upstream region and in the magnetosheath around noon. We conclude that energetic ion events including ions accelerated in the magnetosphere are dominant. Ions accelerated in the magnetosphere leak out from the duskside magnetopause, in particular when geomagnetic activity is high, and then most likely mix with ions accelerated at the bow shock on the way to the dawnside upstream region. The acceleration site of the HCS events is also discussed.

    DOI: 10.1029/2003JA009953

    Web of Science

  109. A comparative analysis of low-latitude Pi2 pulsations observed by Orsted and ground stations 査読有り

    DS Han, T Iyemori, M Nose, H McCreadie, YF Gao, FX Yang, S Yamashita, P Stauning

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   109 巻 ( A10 )   2004年10月

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

    [1] Orsted is a low-altitude polar orbiting satellite, which is advantageous for investigating the spatial structure of low-frequency events like Pi2 pulsations. Using 1-s vector magnetic field data from April 1999 to May 2002 obtained from Orsted and Kakioka magnetic observatories, we found that the field aligned component (Bparallel to) of Pi2 pulsations at the satellite height is highly correlated with the H component on the ground, but the other two components, i.e., eastward component (B-E) and radial component (B-R), do not show a clear correlation with the ground observations. The observed results for nightside events provide evidence that nightside Pi2s at low latitude are generated from cavity resonance. Two cases observed by Orsted when it was located on the dawnside or duskside also show cavity resonance properties. However, when Orsted was on the dayside, the oscillations observed by the satellite are out of phase with that observed on the ground, suggesting that the dayside Pi2s are more likely related to some dayside ionospheric current systems rather than that caused by a global cavity resonance mode. The amplitude variation recorded by Orsted shows a peak in the equatorial region, which, for the first time, gives clear observational support for earlier model calculations. We also estimated the screening effect of the ionosphere on MHD waves and suggest that when the cavity resonance mode is valid for generation of Pi2 pulsations at low latitudes, the screening effect is negligible; that is, the compressional waves are seen directly as Pi2 pulsations at the ground.

    DOI: 10.1029/2004JA010576

    Web of Science

  110. Change of the plasma sheet ion composition during magnetic storm development observed by the Geotail spacecraft 査読有り

    M Nose, RW McEntire, SP Christon

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003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  

    [1] The present study aims to investigate how and where ions of ionospheric origin are accelerated to the ring current energy (a few tens to a few hundreds of keV) and how they are supplied to the ring current. We examined the plasma sheet ion composition during magnetic storm development, using energetic (9-210 keV) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. We selected two magnetic storms, that is, the 16-17 May 2000 storm and the 25 December 1998 storm, for which the energy density ratios of O+/H+ and He+/H+ in the plasma sheet were calculated from the EPIC/STICS data. These magnetic storms had a minimum of the SYM-H index (the 1-min Dst index) less than -50 nT and a duration of the main phase shorter than 6 hours. We obtained the following results: (1) Both the O+/H+ and He+/H+ energy density ratios were anticorrelated with the SYM-H index (\r\ = 0.73-0.88); (2) The O+ /H+ energy density ratio was rather constant at similar to0.1 before storms, but reached 0.3-1.0 at the storm maximum; and (3) The He+ /H+ energy density ratio increased from 0.01-0.02 before storms to 0.04-0.1 at the storm maximum. These ion composition changes are comparable to those in the ring current, which have been reported by previous studies, indicating that ions of ionospheric origin are possibly convected to the ring current via the plasma sheet. A close inspection of ion energy spectra revealed that the observed ion composition changes can be attributed to the mass-dependent acceleration of ions by the dawn-to-dusk electric field in the current sheet and the additional transport of ionospheric ions into the plasma sheet.

    DOI: 10.1029/2002JA009660

    Web of Science

  111. CRRES electric field study of the radial mode structure of Pi2 pulsations 査読有り

    K Takahashi, DH Lee, M Nose, RR Anderson, WJ Hughes

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003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  

    The radial mode structure of Pi2 pulsations in the inner magnetosphere (L&lt;7) and its relation to the plasmapause are studied using data acquired by the Combined Release and Radiation Effects Satellite (CRRES) between August 1990 and September 1991. Low-latitude Pi2 pulsations detected on the ground at Kakioka (L=1.25) are used as the reference signal to determine the relative amplitude and phase of the electric field oscillations detected at CRRES. The plasmapause is identified using electron density inferred from the plasma wave spectra observed on CRRES. Pi2 events at CRRES are defined to be 10-min intervals of high coherence between oscillations in the Kakioka horizontal northward magnetic field (H) and CRRES dusk-to-dawn electric field (E-&phi;) components within the Pi2 band (6-25 mHz). The E-&phi; component represents the poloidal oscillation of the geomagnetic field lines for satellite local times near midnight. Fifty-five high-coherence E-&phi;-H Pi2 events occurred when both CRRES and Kakioka were within 3 hours of magnetic midnight. For these events CRRES was on L shells ranging from 2 to 6.5 and was either in the plasmasphere or in the close vicinity of the plasmapause, providing evidence for the plasmaspheric origin of low-latitude Pi2 pulsations. The amplitude of E-&phi; varied significantly but there is an indication of a maximum near L=4. The phase of E-&phi; (relative to Kakioka H) remained near -90&DEG; at all distances. These properties are consistent with the radial structure of the fundamental cavity mode oscillations confined in the plasmasphere. For some events observed at L&gt;3.5 it was also possible to determine the amplitude and phase of the compressional component B-z at CRRES. In contrast to E-phi, the phase of B-z (relative to H) was clustered both at similar to180 and similar to0 for events occurring near the plasmapause. This observation still is consistent with the cavity mode according to a numerical simulation using a dipole magnetic field and a realistic plasmapause plasma density structure, which indicates that the node of B-z is located near the plasmapause. Depending on the satellite position relative to the node, the phase can be either -180degrees or 0. A negative correlation is found between the Pi2 frequency and the distance of the plasmapause, which is additional support for the cavity mode origin of low-latitude Pi2 pulsations.

    DOI: 10.1029/2002JA009761

    Web of Science

  112. Change of the plasma sheet ion composition during magnetic storm development observed by the Geotail spacecraft 査読有り

    M Nose, RW McEntire, SP Christon

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003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  

    [1] The present study aims to investigate how and where ions of ionospheric origin are accelerated to the ring current energy (a few tens to a few hundreds of keV) and how they are supplied to the ring current. We examined the plasma sheet ion composition during magnetic storm development, using energetic (9-210 keV) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. We selected two magnetic storms, that is, the 16-17 May 2000 storm and the 25 December 1998 storm, for which the energy density ratios of O+/H+ and He+/H+ in the plasma sheet were calculated from the EPIC/STICS data. These magnetic storms had a minimum of the SYM-H index (the 1-min Dst index) less than -50 nT and a duration of the main phase shorter than 6 hours. We obtained the following results: (1) Both the O+/H+ and He+/H+ energy density ratios were anticorrelated with the SYM-H index (\r\ = 0.73-0.88); (2) The O+ /H+ energy density ratio was rather constant at similar to0.1 before storms, but reached 0.3-1.0 at the storm maximum; and (3) The He+ /H+ energy density ratio increased from 0.01-0.02 before storms to 0.04-0.1 at the storm maximum. These ion composition changes are comparable to those in the ring current, which have been reported by previous studies, indicating that ions of ionospheric origin are possibly convected to the ring current via the plasma sheet. A close inspection of ion energy spectra revealed that the observed ion composition changes can be attributed to the mass-dependent acceleration of ions by the dawn-to-dusk electric field in the current sheet and the additional transport of ionospheric ions into the plasma sheet.

    DOI: 10.1029/2002JA009660

    Web of Science

  113. Multipoint observations of a Pi2 pulsation on morningside: The 20 September 1995 event 査読有り

    M Nose, K Takahashi, T Uozumi, K Yumoto, Y Miyoshi, A Morioka, DK Milling, PR Sutcliffe, H Matsumoto, T Goka, H Nakata

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003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 investigated a Pi2 pulsation that occurred at 0538 UT on 20 September 1995, using data from ground stations and the ETS-VI and EXOS-D satellites. Since ground stations at L=1.45-12.6 and the two satellites were located at 7-10 hours of magnetic local time (MLT), we could investigate characteristics of the morning side Pi2 pulsation in detail. We also examined geomagnetic field data from equatorial and low-latitude (Lless than or equal to1.5) stations at 0200 MLT and 1500 MLT. Our findings include the following: (1) Pi2 pulsations on the morning side were observed over a wide range of L (L&lt;6.1) with almost identical period (T&SIM;70 s) and waveforms; (2) the ETS-VI satellite located above the geomagnetic equator at L=6.3 observed a Pi2 pulsation that had nearly the same period and waveforms as the ground Pi2 pulsation; (3) the Pi2 pulsation observed by ETS-VI appeared in the compressional and radial components; (4) phase lag between the compressional and radial components was &SIM;180&DEG; (5) the ground-to-satellite phase lag was &SIM;180&DEG; (&SIM;0&DEG;) for the X component and the compressional (radial) component; (6) the EXOS-D observation placed the plasmapause location at L=6.8, across which ground Pi2 pulsations changed their characteristics; and (7) no phase delay was found between low-latitude Pi2 pulsations observed around 0700 MLT, 0200 MLT, and 1500 MLT. From these results we concluded that the morning side Pi2 pulsation was caused by the plasmaspheric cavity mode resonance and that its longitudinal structure was rather uniform.

    DOI: 10.1029/2002JA009747

    Web of Science

  114. Local time dependence of the frequency of Pi2 waves simultaneously observed at 5 low-latitude stations 査読有り

    DS Han, T Iyemori, YF Gao, YH Sano, FX Yang, WS Li, M Nose

    EARTH PLANETS AND SPACE   55 巻 ( 10 ) 頁: 601 - 612   2003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  

    One-second resolution geomagnetic data from 5 stations located at low-latitudes (i.e., L = 1.2 similar to 1.6) were used to examine the local time dependence of the dominant frequency of Pi2 pulsations. We analyzed 183 Pi2 events simultaneously recorded at the 5 stations and discussed their possible generation mechanisms. The averaged dominant frequency of the H (horizontal) component is higher on the dawn side than that on the dusk side and shows a peak value in the post-midnight at around 03 LT, which confirms the LT dependence previously suggested from single station data (i.e., non-simultaneous observation). However, some of the events have no LT dependence. For the events which show the LT dependence at low-latitudes, we infer that the cavity resonance mode is a plausible generation mechanism, but we do not rule out the possibility of the plasmaspheric surface wave mode which has also been suggested. For the events having a common frequency between the eastern and western stations, we suggest the cavity resonance mode to be the mechanism. The averaged dominant frequency of the D component does not show any clear LT dependence, and only about 20% of Pi2s have identical frequency for both the H and D components, therefore we suggest that the H and D oscillations of Pi2s are generated from different mechanisms. We also found that the frequency of different parts of a Pi2 pulsation, i.e., the dominant frequency for leading part and trailing part of the pulsation, is different, and the frequency of the trailing part is lower than that of the leading part.

    DOI: 10.1186/BF03352467

    Web of Science

    CiNii Article

    J-GLOBAL

  115. Quiet time magnetotail dynamics and their implications for the substorm trigger 査読有り

    S Ohtani, R Yamaguchi, M Nose, H Kawano, M Engebretson, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   107 巻 ( A2 )   2002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  

    [1] The present study seeks to systematically examine the fast plasma flow in the plasma sheet at geomagnetically quiet time. The study uses plasma measurements made by the Geotail satellite in the midnight sector at x &gt; -50 R-E during quiet intervals with a total duration of 446 hours. Comparison with the results of previous studies suggests that the occurrence frequency of the perpendicular flow velocity V-Xperpendicular to depends more clearly on the radial distance than on geomagnetic activity. Two extreme events were selected for detailed studies; they occurred on 23 November and 10-11 December 1994. In the 23 November event, Geotail was located similar to37 R-E from Earth and observed a fast tailward flow (V-Xperpendicular to similar to -1250 km s(-1)) with a strongly southward magnetic field (B-Z similar to -8.9 nT). The signature indicates that a near-Earth neutral line was formed earthward of the satellite and the reconnection reached the lobe magnetic field. On the ground, however, only weak (&lt; 100 nT) magnetic disturbances were observed at high (&SIM;75&DEG;) latitudes but not at auroral zone stations. The result strongly suggests that lobe reconnection is not sufficient for the global development of a substorm. The 10-11 December 1994 event is very similar to the 23 November 1994 event except that Geotail observed a fast (V-X&BOTTOM; &SIM; +1500 km s(-1)) earthward flow rather than a tailward flow, along with the dipolarization of the local magnetic field. It is asserted that the near-Earth substorm process, that is, tail current disruption, controls the development of a substorm. The fast plasma flow may set a favorable condition for this process to proceed, and therefore the substorm may tend to develop following generation of the fast flow, but the result of the present study indicates that near-Earth reconnection does not necessarily trigger the global substorm.

    DOI: 10.1029/2001JA000116

    Web of Science

  116. Local time dependence of the dominant frequency of Pi2 pulsations at mid- and low-latitudes 査読有り

    K Kosaka, T Iyemori, M Nose, M Bitterly, J Bitterly

    EARTH PLANETS AND SPACE   54 巻 ( 7 ) 頁: 771 - 781   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    We carried out a statistical analysis of Pit pulsations using the geomagnetic field data obtained at three ground stations. A local time dependence of the dominant frequency of Pit was found on the nightside. The frequency of mid-latitude Pit pulsations is lower on the dusk side than that on the dawn side. This tendency is attributed to the shape of the plasmasphere which bulges out to the dusk side. It was confirmed that the Pit frequency depends also on the geomagnetic activity measured with Kp index. During the disturbed periods, Pit pulsations have higher frequency than that in the quiet periods. This dependence is interpreted to be caused by the size of the plasmapause which is smaller under the disturbed conditions than that under the quiet conditions. The dominant frequency of Pit pulsations at lower latitudes has a peak in post-midnight, and a Kp dependence similar to that at mid-latitudes is also observed. However, the result for low-latitude Pit's is different from that for mid-latitude Pit. We consider that the dominant mechanism of mid-latitude Pit is the plasmaspheric surface wave. In order to examine the idea that the surface wave on the plasmapause is the dominant mechanism of Pit pulsations at mid-latitudes, we estimated the resonance frequency of the surface wave on the plasmapause using a plasmaspheric model which includes the effect of the plasmaspheric bulge. The estimated frequency of the surface wave is higher on the dawn side than that on the dusk side, which is essentially consistent with the observational results. The predicted frequency under quiet conditions (Kp less than or equal to 3) is nearly equal to the observed Pit frequency at mid-latitudes. These results suggest that the dominant frequency of Pit pulsations at mid-latitudes depends on the structure of the plasmapause.

    DOI: 10.1186/BF03351730

    Web of Science

    CiNii Article

    J-GLOBAL

  117. Storm-substorm relationship: Contribution of the tail current to Dst

    Ohtani S.

    Journal of Geophysical Research: Space Physics   106 巻 ( A10 ) 頁: 21199 - 21209   2001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:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2000ja000400

    Scopus

  118. Storm-substorm relationship: Contribution of the tail current to Dst 査読有り

    S Ohtani, M Nose, G Rostoker, H Singer, ATY Lui, M Nakamura

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A10 ) 頁: 21199 - 21209   2001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 Dst index has been conventionally used as a measure of the storm intensity, which ideally assumes that the associated ground magnetic disturbance is caused by the ring current. The present study examines the contribution of the tail current to Dst, focusing on the occurrence of geosynchronous dipolarization close to the Dst minimum, in other words, the start of the storm recovery phase. The Sym-H (referred to as Dst((Sy-H)) hereafter) index rather than the conventional Dst index is used because of its higher time resolution (1 min). For the June 1998 storm event, dipolarization started at two GOES satellites and the Geotail satellite in the near-Earth tail when Dst((Sym-H)) reached its minimum. This result indicates that the source current was located outside of geosynchronous orbit, and therefore the recovery of Dst((Sym-H)) can be attributed to the reduction of the tail current rather than the decay of the ring current. A statistical study based on 59 storm events (79 GOES events) confirms the tendency for geosynchronous magnetic field to dipolarize at the Dst((Sym-H)) minimum. It is therefore highly likely that the Dst((Sym-H)) minimum is misidentified as the start of the ring current (storm) decay at a time when the ring current may actually be intensifying owing to substorm-associated injection, From the magnitude of the Dst((Sym-H)) recovery during the interval of geosynchronous dipolarization, the contribution of the tail current to Dst((Sym-H)) at the Dst((Sym-H)) minimum is estimated to be 20-25%. However, the contribution of the tail current may be even larger because the tail current may not return to preintensification levels and may continue to contribute to Dst(sym-fn after dipolarization. The trigger of dipolarization (substorm) and the subsequent recovery of Dst((Sym-H)) tend to take place in the course of the reduction of the southward interplanetary magnetic field (IMF) B-Z. It is therefore suggested that the ring current (storm) recovers after the substorm since the magnetospheric convection weakens because of weaker southward IMF B-Z.

    DOI: 10.1029/2000JA000400

    Web of Science

  119. Ion composition of the near-Earth plasma sheet in storm and quiet intervals: Geotail/EPIC measurements 査読有り

    M Nose, S Ohtani, K Takahashi, ATY Lui, RW McEntire, DJ Williams, SP Christon, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A5 ) 頁: 8391 - 8403   2001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 investigate the ion composition of the near-Earth plasma sheet in storm and quiet intervals, using energetic (9-210 keV) particle flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. In 1998 four magnetic storms (minimum Dst &lt; -50 nT) occurred when Geotail was located in the near-Earth plasma sheet (X greater than or equal to -10 R-E) For each of the storms, we have selected a col responding quiet interval from time periods when Geotail revisited the near-Earth plasma. sheet under the condition Dst &gt; -20 nT, The energy density of the H+, He+, and O+ ions was computed from the EPIC/STICS data for these storm and quiet-time events. We obtained. the following results: (1) The energy density is higher during storms than during quiet times for all ion species (H+, He+, and O+); (2) the He+/H+ energy density ratio during storms is 0.01-0.02, while that, during quiet times is similar to0.01; and (3) the O+/H+ energy density ratio is significantly larger during storms (0.2-0.6) than during quiet times (0.05-0.1). To explain these results we suggested a current sheet acceleration mechanism in which ions are energized by the dawn-to-dusk convection electric field in a mass-dependent way in the course of interaction with the current sheet.

    DOI: 10.1029/2000JA000376

    DOI: 10.1029/2000ja000376

    Web of Science

  120. Composition of energetic neutral atoms during a storm main phase 査読有り

    ATY Lui, RW McEntire, M Nose, DJ Williams

    GEOPHYSICAL RESEARCH LETTERS   28 巻 ( 7 ) 頁: 1363 - 1366   2001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:AMER GEOPHYSICAL UNION  

    The first composition observation of energetic neutral atom (ENA) emissions during the main phase of a geomagnetic storm is reported here. The measurements were made by the Energetic Particles and Ion Composition (EPIC) instrument on the Geotail on October 22, 1999 when the ring current was strengthening. For this geomagnetic storm, while the Dst index was monotonically decreasing during the main phase, ENA fluxes showed two major enhancements with distinctly different temporal profiles. For the first enhancement, the increases in ENA fluxes were rapid and the subsequent evolution was species dependent. Both the integral ENA (E &gt;similar to 12 keV) and neutral hydrogen (E &gt; 67 keV) fluxes remained relatively unchanged after the increase while the neutral oxygen (E &gt; 203 keV) fluxes decreased rapidly. For the second enhancement, the increases in ENA fluxes of all species were rather gradual and the subsequent decrease in the neutral oxygen flux was also slow. The slow decrease may be related to the continual AE enhancement during that time. For total energies above 200 keV, the intensity of ENA oxygen was the highest, followed by hydrogen, and then by helium. This ordering of ENA intensity for these species is similar to the previous ENA composition results obtained for the recovery phase of another geomagnetic storm.

    DOI: 10.1029/2000GL012612

    Web of Science

  121. Convection enhancements in the low-latitude lobe for substorm onset 査読有り

    S Taguchi, M Kiyohara, T Mukai, M Nose, Y Saito

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A3 ) 頁: 3943 - 3952   2001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  

    Characteristics of the lobe plasma convection enhancements around Pi2 substorm onset have been clarified with Geotail data. We identified 92 lobe substorm onset events within 5 R-E from an estimated neutral sheet from X = -10 to -35 R-E, and we found 27 convection enhancement events. These events were categorized into two types depending on whether the magnetic field tilts northward or southward in coincidence with intensity. decrease. The former type was identified in 12 of the 27 and found to be generally at shorter distances from the Earth than the latter, The frequencies of the lobe observations in the above Z width are small (less than or equal to 11%); that is, the plasma sheet usually occurs. In this situation, 80%: of the 27 are identified only within 2.5 R-E from the estimated neutral sheet. This indicates that the convection enhancement events occur. in association with the lobe appearance in the vicinity of the neutral sheet. This is also recognized in the X-Y distribution of the lon-latitude lobe observation; the relatively high frequencies of greater than or equal to4% which have a dawn-dusk asymmetry roughly correspond to the event location. Examination of the convection speed shows that the peak lies in 0.04V(A) to 0.1V(A) (V-A is the local Alfven velocity) and that the duration is 1 - 3 min for most cases. Identification probability of the convection enhancement events nas also examined. Both types of events have very similar occurrence probability in Y = 0-10 R-E, which is consistent with an interpretation that both are created by a common process, i,e,, lobe reconnection in the near-Earth neutral line (NENL). For the downside of this Y region, however, the southward field tilting type more often appears than he other, implying that the convection enhancements occur in an asymmetric manner with respect to the NENL.

    DOI: 10.1029/2000JA900097

    DOI: 10.1029/2000ja900097

    Web of Science

  122. Change of energetic ion composition in the plasma sheet during substorms 査読有り

    M Nose, S Ohtani, ATY Lui, SP Christon, RW McEntire, DJ Williams, T Mukai, Y Saito, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A10 ) 頁: 23277 - 23286   2000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  

    It I-las been reported by previous studies that the energetic particle flux of ions of ionospheric origin like O+ ions is more enhanced than that of Hf ions in the near-Earth tail (X similar to-6 to -16 R-E) during substorms. To explain this strong O+ flux enhancement, some studies have surmised that thermal O+ ions in the plasma sheet boundary layer or the lobe are strongly accelerated at the magnetic reconnection region (X similar to-20 to -30 R-E), and are subsequently transported into the near-Earth plasma sheet; with earthward plasma flows. However, other studies have supposed that the strong O+ flux enhancement is caused by local magnetic field reconfiguration (local dipolarization). In the present study, we used Geotail/EPIC measurements of energetic (60 keV to 3.6 MeV) ion flux to test the above two scenarios. We investigated ion composition in the plasma sheet while earthward plasma flows and/or dipolarization signatures were observed. In terms of energy density ratio of oxygen ions to protons, the observational results can be summarized as follows: (1) earthward plasma flows without dipolarization signatures did not accompany large increases of the ratio in most cases; (2) when earthward plasma flows appeared with dipolarization signatures, they accompanied increases of the ratio; and (3) most of dipolarization events were associated with large increases of the ratio. These results suggest that the strong increase in the energetic oxygen constituent in the near-Earth plasma sheet is due to acceleration of ions during dipolarization, consistent with the latter scenario.

    DOI: 10.1029/2000JA000129

    DOI: 10.1029/2000ja000129

    Web of Science

  123. Acceleration of oxygen ions of ionospheric origin in the near-Earth magnetotail during substorms 査読有り

    M Nose, ATY Lui, S Ohtani, BH Mauk, RW McEntire, DJ Williams, T Mukai, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A4 ) 頁: 7669 - 7677   2000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:AMER GEOPHYSICAL UNION  

    Measurements from the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft were used to investigate dynamics of O+ ions of ionospheric origin at energies of 9 keV to 210 keV in the near-Earth plasma, sheet during the substorm expansion phase. Substorm signatures were clearly observed on the ground at 1850 UT on May 17, 1995. In the expansion phase of this substorm, Geotail stayed in the plasma sheet at X similar to-10.5 R-E and observed a local dipolarization signature accompanied by strong disturbances of the magnetic field. From the energetic ion flux data of EPIC/STICS, we obtained the following results: (1) energetic flux enhancement was more pronounced for O+ than for H+; (2) the flux was enhanced almost simultaneously with local dipolarization; (3) the enhancement factor of O+ ions (EO+), which represents the enhancement of the O+ flux ratio (after and before substorm onset) relative to the H+ flux ratio, was Bs large as 1.31; and (4) thermal energy increased from 8.9 keV to 42.8 keV for O+ ions and from 9.4 keV to 15.9 keV for H+ ions. We also performed statistical analysis for 35 events of local dipolarization found in the near-Earth region (X similar to-6 to -16 R-E). We found that EO+ is larger than unity in all ranges of radial distance and that the average value of EO+ is 1.37. These results suggest that O+ ions are commonly more energized than H+ ions during the substorm expansion phase. To interpret these observational results, we propose a mechanism in which ions are accelerated in a non-adiabatic way during substorm-associated field reconfiguration.

    DOI: 10.1029/1999JA000318

    DOI: 10.1029/1999ja000318

    Web of Science

  124. Near-Earth dipolarization: Evidence for a non-MHD process 査読有り

    Lui A.T.Y.

    Geophysical Research Letters   26 巻 ( 19 ) 頁: 2905 - 2908   1999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:Geophysical Research Letters  

    DOI: 10.1029/1999GL003620

    DOI: 10.1029/1999gl003620

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    Scopus

  125. Automated detection of Pi 2 pulsations using wavelet analysis: 2. An application for dayside Pi 2 pulsation study 査読有り

    M Nose

    EARTH PLANETS AND SPACE   51 巻 ( 1 ) 頁: 23 - 32   1999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 investigated statistical characteristics of dayside Pi 2 pulsations observed at Mineyama (25.5 degrees geomagnetic latitude) from November 1994 through June 1996, using an algorithm to detect Pi 2 pulsations which was introduced in Part I of the accompanying paper. We obtained the following results. (1) The ratio of the number of Pi 2 pulsations on the dayside (06-18 MLT) to that on the nightside (18-06 MLT) was about 31%. (2) The polarization of the dayside Pi 2 pulsations changed from right-handed before local noon to left-handed after local noon. (3) Wave power of dayside Pi 2 pulsations in the H-component has a peak around local noon and dips on both dawn and dusk sides. (4) Frequency of the fundamental wave is ranging from 9 mHz to 30 mHz with dominant frequency of 17-24 mHz, and frequency ratios of the first three harmonics are 1 : (1.7 +/- 0.5) : (2.3 +/- 0.7). We found that the magnetospheric cavity model can explain most of these observational results.

    DOI: 10.1186/BF03352206

    Web of Science

    J-GLOBAL

  126. Geotail observations of north-south plasma velocity enhancements in the lobe near substorm expansion phase onset 査読有り

    S Taguchi, M Kiyohara, T Mukai, T Yamamoto, M Nose, Y Saito, S Kokubun

    GEOPHYSICAL RESEARCH LETTERS   25 巻 ( 22 ) 頁: 4125 - 4128   1998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  

    This paper reports on the enhancement of the lobe plasma velocity towards the neutral sheet. Analyzing the Geotail plasma and magnetic field data in the lobes earthward of X = -45 R-E, we identified 30 events of several-minute magnetic field increase-and-decrease during which the field tilts only southward; that is, the B-Z variation is unipolar. For most of these events, we found that the lobe plasma velocity towards the neutral sheet is enhanced and peaked around the most southward tilting of the field. The average of the peak magnitude is about 130 km/s in a plane perpendicular to the magnetic field. For each case, this magnitude is roughly 1 - 10 % of the lobe Alfven speed. We interpret the velocity enhancement having these characteristics as sig-natures of the transition from plasma sheet reconnection to lobe reconnection at the near-Earth neutral line.

    DOI: 10.1029/1998GL900132

    DOI: 10.1029/1998gl900132

    Web of Science

    Scopus

  127. Temporal relationship between midtail traveling compression regions and substorm onset: Evidence for near-Earth neutral line formation in the late growth phase 査読有り

    S Taguchi, JA Slavin, M Kiyohara, M Nose, GD Reeves, RP Lepping

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A11 ) 頁: 26607 - 26612   1998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  

    The timing of the near-Earth neutral line (NENL) formation relative to substorm onset signatures has been a central debate in substorm research for some time. Several recent studies have suggested that the direct identification of the reconnection site, at least in its initial stage, is difficult because it may be a very limited region spatially. Our approach to this timing problem is the examination of the midtail lobe traveling compression regions (TCRs) relative to onset during substorm events. Fifty-nine midtail TCRs in the IMP 8 magnetotail observations are analyzed. These midtail TCRs differ from the distant tail TCRs in that they lack the first half of the north and south tilting of the field during the compression. The flat B-Z phase preceding the south tilting interval in these midtail compression regions has been interpreted as being due to the close proximity to the growing plasmoid bulge just prior to plasmoid ejection down the tail. The results of our analysis show that these TCRs start a few minutes before or simultaneously (accuracy of 1 min) with Pi2 onset at low-latitude or midlatitude ground stations and the particle injection at the geosynchronous orbit. Before the plasmoid bulge formation starts, the NENL must start to form in the plasma sheet; that is, the formation of NENL must initially occur on closed field lines to form the plasmoids which compress the lobes to cause the TCRs. Our results support this view and allow us to conclude that NENL forms before ground and geosynchronous substorm onset signatures, i.e., in the late growth phase. The implications of these results for magnetospheric substorm models are discussed.

    DOI: 10.1029/98JA02617

    DOI: 10.1029/98ja02617

    Web of Science

  128. Electron precipitation accompanying Pc 5 pulsations observed by the DE satellites and at a ground station 査読有り

    M Nose, T Iyemori, M Sugiura, JA Slavin, RA Hoffman, JD Winningham, N Sato

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A8 ) 頁: 17587 - 17604   1998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 data from the polar orbiting Dynamic Explorer (DE) -1 and -2 satellites and a ground-based station, we investigated electron precipitation phenomena accompanying Pc 5 pulsations. DE-2 observed oscillatory disturbances in the magnetic and electric fields in the upper ionosphere at the geomagnetic footprint of the high altitude region in which transverse Pc 5 pulsations were detected by DE-1. DE-2 observed electrons precipitating into the ionosphere with energies of several keV to several tens of keV, These electrons were accelerated in the direction of the ambient magnetic field. When Pc 5 pulsations in the H-component and periodic variations of cosmic radio noise absorption (CNA pulsations) were observed at Syowa Station, DE-2 which was in geomagnetic conjunction with Syowa Station also observed oscillatory disturbances in the magnetic and electric fields. These oscillatory disturbances are caused by small-scale field-aligned currents each with. width of 0.5 degrees-1.4 degrees invariant latitude. This suggests that Pc 5 pulsations have a small-scale resonance structure in the radial direction. The resonance structure has a small scale comparable to the ion acoustic gyroradius, then kinetic Alfven waves having electric fields parallel to the ambient magnetic field can arise. The parallel electric field generates a field-aligned potential drop of about 3-5 kV. Electrons accelerated by these kinetic Alfven waves would cause CNA pulsations, the phase of which leads that of the B-component of the Pc 5 pulsations by 90 degrees in the southern hemisphere. This is consistent with the observations at Syowa Station.

    DOI: 10.1029/98JA01187

    DOI: 10.1029/98ja01187

    Web of Science

  129. Application of discovery science to solar-terrestrial physics 査読有り

    T Araki, T Iyemori, M Nose, T Wada, Y Futaana, G Ueno, T Kamei, A Saito

    DISCOVERY SCIENCE   1532 巻   頁: 451 - 452   1998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-VERLAG BERLIN  

    Tohru Araki, Toshihiko Iyemori, Masahito Nose, Takaaki Wada, Yoshifumi Futaana, Genta Ueno, Toyohisa Kamei, Akiniro Saito, 1998, &#039;Application of Discovery Science to Solar-Terrestrial Physics&#039;, &lt;i&gt;Discovey Science&lt;/i&gt;, pp. 451-452

    DOI: 10.1007/3-540-49292-5_66

    Web of Science

  130. Automated detection of Pi 2 pulsations using wavelet analysis: 1. Method and an application for substorm monitoring 査読有り

    M Nose, T Iyemori, M Takeda, T Kamei, DK Milling, D Orr, HJ Singer, EW Worthington, N Sumitomo

    EARTH PLANETS AND SPACE   50 巻 ( 9 ) 頁: 773 - 783   1998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  

    Wavelet analysis is suitable for investigating waves, such as Pi 2 pulsations, which are limited in both time and frequency. We have developed an algorithm to detect Pi 2 pulsations by wavelet analysis. We tested the algorithm and found that the results of Pi 2 detection are consistent with those obtained by visual inspection. The algorithm is applied in a project which aims at the nowcasting of substorm onsets. In this project we use real-rime geomagnetic field data. with a sampling rate of 1 second, obtained at mid- and low-latitude stations (Mineyama in Japan, the York SAMNET station in the U.K., and Boulder in the U.S.). These stations are each separated by about 120 degrees in longitude, so at least one station is on the nightside at all times. We plan to analyze the real-time data at each station using the Pi 2 detection algorithm, and to exchange the detection results among these stations via the Internet. Therefore we can obtain information about substorm onsets in real-time, even if we are on the dayside. We have constructed a system to detect Pi 2 pulsations automatically at Mineyama observatory. The detection results for the period of February to August 1996 showed that the rate of successful detection of Pi 2 pulsations was 83.4% for the nightside (18-06MLT) and 26.5% for the dayside (06-18MLT). The detection results near local midnight (20-02MLT) give the rate of successful detection of 93.2%.

    DOI: 10.1186/BF03352169

    Web of Science

    J-GLOBAL

  131. Storm-time magnetic field variations observed by the ETS-VI satellite 査読有り

    N Terada, T Iyemori, M Nose, T Nagai, H Matsumoto, T Goka

    EARTH PLANETS AND SPACE   50 巻 ( 10 ) 頁: 853 - 864   1998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  

    To study the ring current structure in the inner magnetosphere, we have statistically examined the magnetic field data acquired by ETS-VI (the Engineering Test Satellite-VI). During a magnetic storm, the Dst index shows a rapid recovery of its amplitude for about 9 hours on average after the main phase and a subsequent long-lasting slow recovery. We have investigated this "two-step recovery" of the Dst index by obtaining magnetic field vectors and calculating the current structure in the inner magnetosphere for each magnetic storm phase determined by the Dst index. From this study, following results are obtained: (1) Throughout the storm-time, disturbed magnetic fields exhibit clear day-night asymmetry with strong peak in the nightside. (2) During the main phase, southward perturbed field components have a relative bump in the nightside region between similar to 2000 and similar to 0400 MLT and between similar to 4.0 and 6.4 R-E (geocentric distances in Earth radii). (3) The initial rapid recovery of the Dst index is considerably influenced by the nightside currents flowing between similar to 1800 and similar to 0600 MLT and between 5.6 and 7.2 R-E. These currents are thought to be mainly composed of the particles that escape the magnetosphere on the duskside flank, which are simulated in particle tracing in a realistic magnetosphere.

    DOI: 10.1186/BF03352179

    Web of Science

    J-GLOBAL

  132. ULF pulsations observed by the ETS-VI satellite: Substorm associated azimuthal Pc 4 pulsations on the nightside 査読有り

    M Nose, T Iyemori, S Nakabe, T Nagai, H Matsumoto, T Goka

    EARTH PLANETS AND SPACE   50 巻 ( 1 ) 頁: 63 - 80   1998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  

    The magnetic field data from the Engineering Test Satellite-VI (ETS-VI) have been analyzed to investigate the occurrence distributions of pulsations in Pc 3-5 frequency ranges in the magnetosphere. The observation of ETS-VI covered the invariant latitude (ILAT) range of 64.5 degrees-69 degrees ILAT near the geomagnetic equator (-10 degrees-20 degrees magnetic latitude) at all magnetic local time (MLT). Magnetic pulsations were selected by the Fast Fourier Transform method and checked by visual scanning if they have continuous waveforms. From the occurrence distributions of pulsations, we have found distinctive features in the following pulsations: (1) azimuthal Pc 5 pulsation; (2) azimuthal Pc 3 pulsation; (3) radial Pc 4 pulsation on the dayside; (4) azimuthal Pc 4 pulsations on the nightside, In respect of the first three types of pulsations (i.e., the azimuthal Pc 5 pulsation, the azimuthal Pc 3 pulsation, and the radial Pc 4 pulsation on the dayside), the results presented in this study confirm the previous results obtained by other satellite observations. The azimuthal Pc 4 pulsations on the nightside were observed in continuous waveforms lasting for about 10 minutes. Although the azimuthal Pc 4 pulsations on the nightside start at almost the same time as substorm onsets, they are different from Pi 2 pulsations in the magnetosphere. They are observed frequently in the MLT range of 23-04MLT with an occurrence peak at 01-02MLT. We suggest that the azimuthal Pc 4 pulsations on the nightside are excited through coupling to the fast mode Alfven waves which were launched at substorm onset.

    DOI: 10.1186/BF03352087

    Web of Science

    J-GLOBAL

  133. ETS-VI Magnetic Field Observations of the Near-Earth Magnetotail during Substorms 査読有り

    Nagai T.

    Journal of Geomagnetism and Geoelectricity   48 巻 ( 5-6 ) 頁: 741 - 748   1996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:Journal of Geomagnetism and Geoelectricity  

    The magnetic field experiment on board ETS-VI (the Engineering Test Satellite-VI) and initial results from the experiment are presented. ETS-VI was launched on August 28, 1994 and has been placed in anear equatorial orbit with a perigee of 2.3Re, an apogee of 7.1Re, an inclination of 13.4&deg;, and an orbital period of 14.4 hours. The spacecraft is three-axis stabilized. The magnetic field experiment on board the satellite consists of a triaxial fluxgate magnetometer. The magnetometer has a sampling interval of 3 s, and except near perigee, it is operated in the mode having a &plusmn;256 nT dynamic range and a 0.125 nT resolution. We have examined the magnetometer data obtained at radial distances from 5.0 to 7.1Re, magnetic latitudes from-10&deg; to 25&deg;, and local times from 14 MLT through midnight to 04 MLT, to study magnetic field variations associated with substorms. Substorm-associated field variations are easily seen at larger radial distances and at local times later than 19 MLT. Using 92 substorm events that occurred in the 21-01 MLT sector, we have constructed the average field configuration during the growth phase. The magnetic field becomes highly taillike and its intensity increases at high latitudes (> 10&deg;), while the field intensity decreases at lower latitudes (<10&deg;). The field configuration suggests that the inner edge of the growth phase current system is located near the synchronous altitude at the end of the growth phase.

    DOI: 10.5636/jgg.48.741

    Web of Science

    Scopus

    CiNii Article

    J-GLOBAL

  134. Traveling compression region observed in the mid-tail lobes near substorm expansion phase onset 査読有り

    S. Taguchi, J.A. Slavin, R.P. Lepping, M. Nosé

    European Space Agency, (Special Publication) ESA SP   ( 389 ) 頁: 603 - 607   1996年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  135. A STRONG DAWN DUSK ASYMMETRY IN PC5 PULSATION OCCURRENCE OBSERVED BY THE DE-1 SATELLITE 査読有り

    M NOSE, T IYEMORI, M SUGIURA, JA SLAVIN

    GEOPHYSICAL RESEARCH LETTERS   22 巻 ( 15 ) 頁: 2053 - 2056   1995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 the magnetic field data obtained by the DE-1 polar orbiting satellite, statistical characteristics of transverse Pc5 pulsations in the inner magnetosphere are examined. The occurrence distribution is found to have a strong dawn/dusk asymmetry. The occurrence is most frequent in the region around 72 degrees invariant latitude (ILAT) between 0800 and 1000MLT. The distribution shifts to lower ILAT both in the early morning and in the afternoon sectors. Our results are generally consistent with the occurrence distributions obtained by previous studies except for appreciable differences in the local time of the peak occurrence. The dependence of the transverse Pc5 occurrence on solar wind velocity is also investigated. Results show that the higher the solar wind velocity, the more frequent the Pc5 occurrence. This fact suggests that the energy source of these Pc5's is in the Kelvin-Helmholtz instability (KHI) on the magnetopause. To explain the strong dawn/dusk asymmetry, the dependence of the Pc5 occurrence on the angle between the solar wind velocity and the IMP in the ecliptic plane is investigated. It is found that this angle controls the magnetic local time of Pc5 appearance when the solar wind velocity is small. This dependence may be explained by the low threshold of KHI due to an influence of a quasi-parallel bow shock.

    DOI: 10.1029/95GL01794

    DOI: 10.1029/95gl01794

    Web of Science

▼全件表示

書籍等出版物 2

  1. 地磁気観測で探る宇宙空間環境変動

    能勢正仁( 担当: 分担執筆)

    日本磁気学会報「まぐね」  2020年9月 

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    担当ページ:244-254   記述言語:日本語

  2. データ引用を研究活動の新たな常識に:研究データ利活用協議会(RDUF)リサーチデータサイテーション小委員会の活動

    能勢正仁, 池内有為( 担当: 分担執筆)

    国立国会図書館, カレントアウェアネス  2020年9月 

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    担当ページ:2-4  

    DOI: 10.11501/11546850

科研費 25

  1. 多様な学術研究活動を育むアカデミックデータ・イノベーション成熟度モデルの開発

    研究課題/研究課題番号:20H00099  2020年4月 - 2023年3月

    梶田 将司

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    担当区分:研究分担者 

    大学における研究データの蓄積・共有・公開及び長期保管を通じて,研究者自らが研究データマネジメントスキル (RDMスキル) を高められるとともに,研究データを軸とした研究コミュニティ形成や異分野連携を可能にするアカデミックデータ・イノベーション成熟度モデルを開発する.本モデルは,研究者が日常的に行う基本RDMスキル,分野ごとに特有のRDMスキル,分野横断型のイノベーションを創発するRDMスキルの3スキル及びこれらのスキル開発方法論により構成される.本研究では,多様な分野の研究者が集う京都大学を実証フィールドとして開発することにより,イノベーションの可能性に満ちた土壌を我が国の学術研究現場に育む.

  2. プラズマ圏極端収縮時の放射線帯消失の撮像

    研究課題/研究課題番号:19H01958  2019年4月 - 2024年3月

    尾花 由紀

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    担当区分:研究分担者 

    本研究では、ニュージーランドに新しく高感度全天カメラと誘導磁力計を設置し、放射線帯降下粒子による孤立オーロラの発光と、粒子降下を引き起こすイオンサイクロトロン(EMIC)波動を同時観測することで、以下の科学目標の達成を目指す。
    (1) 地球にごく近い深部磁気圏において、EMIC波動に起因する放射線帯消失が生じていることを立証する。
    (2) 地磁気嵐に伴うプラズマ圏の収縮と放射線帯消失の因果関係を解明する。
    (3) 放射線帯粒子降下による中緯度超高層大気組成への影響評価を行う。
    本研究は、ニュージーランドのミドルマーチ観測点(磁気緯度: -53度, L値: 2.8(磁力線の到達距離が地球半径の 2.8倍の位置))に新しく 高感度全天カメラと誘導磁力計を設置し、放射線帯降下粒子による孤立オーロラの発光と、粒子降下を引き起こすイオンサイクロトロン波動を同時観測することで、以下の科学目標の達成を目指すものである。
    (1) 地球にごく近い深部磁気圏において、イオンサイクロトロン波動に起因する放射線帯消失が生じて いることを立証する。
    (2) 地磁気嵐に伴うプラズマ圏の収縮と放射線帯消失の因果関係を解明する。
    (3) 放射線帯粒子降下による中緯度超高層大気組成への影響評価を行う。
    初年度である2019年度は、過去の観測例を洗い出し、中緯度帯(L < 3)(地球半径の 3 倍以下の位置)のニュージーランドにおけるイオンサイクロトロン波動の周波数と振幅の予想を立て、高感度誘導磁力計に求められるスペックを決定して、購入するインダクションコイルの選別を慎重に行った。その結果、Metronix社製ADU-08eおよびインダクションコイルMFS-06e 2本を購入し、南北・東西方向に設置するのが最低であるとの結論を得た。これらの機器を購入後、高感度誘導磁力計と孤立オーロラ観測用の高感度カメラの観測システムを開発し、高感度誘導磁力計システムについては、名古屋大学稲生地殻変動観測所にて動作確認を行った。さらに大阪電気通信大学内にて、長期動作中の消費電力量のテスト等を行い、太陽電池給電システムの仕様を決定し、必要な太陽電池パネルの発電量や蓄電装置の電気容量等を算出し、在ニュージーランドの現地協力者に必要物品の手配を依頼した。これらの準備が整ったのち、ニュージーランドに出張し、ミドルマーチ観測点にて設置作業を行なった。
    当初の予定では、1年目はスペックの決定後、誘導磁力計を購入し、観測システムを開発し、現地での設置場所の下見を行う予定であった。さらに2年目に誘導磁力計を仮設置し、3年目に本格的な定常観測を開始する計画であった。しかしながら、観測システムの開発が予定以上にスムーズに進行し、電源供給システムについても既存の技術が適合したため開発スケジュールを前倒しすることができた。また現地においても、地主との交渉がスムーズに行え、すぐに掘削する許可を得ることができた上、良好な観測場所も見つけることができた。そのために、予定を繰り上げて2020年3月の現地訪問時に本設置を行うこととし、現地作業を無事済ませることができた。
    これにより、2年目以降はデータ解析に注力することができる体制となった。
    本研究計画の鍵となる誘導磁力計とオーロラ高感度カメラを2020年3月にミドルマーチ観測店に設置したが、その後新型コロナウイルスの流行により、ニュージーランドでは市民の外出規制が行われており、最初の観測データがいまだ回収できていない状況にある。外出規制が解かれたのち速やかに現地協力者にデータの回収と日本への送付を行ってもらう予定である。
    データが入手でき次第、EMIC波動の解析に着手する。特に「あらせ」衛星との共役観測データについては優先的に解析を行う予定である。またプロトタイプ の数値計算モデルを使って EMIC 波動と共鳴することができる荷電粒子のエネルギー (共鳴エネルギー)を導出し、この情報を入力として、オーロラ発光の強度とスペクト ルを計算する。
    さらにこれらの理論的推定値に基づき、観測装置のセッティングを調整するための現地作業を行う予定である。

  3. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:18HP8018  2018年4月 - 2019年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:1700000円

  4. 磁気インピーダンスセンサーによる地磁気観測実験と稠密観測網展開可能性の探索

    研究課題/研究課題番号:17K18804  2017年6月 - 2021年3月

    挑戦的研究(萌芽)

    能勢 正仁

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    担当区分:研究代表者 

    配分額:6370000円 ( 直接経費:4900000円 、 間接経費:1470000円 )

    磁気インピーダンス(Magneto-Impedance (MI))センサーのメーカーであるアイチマイクロインテリジェント社の技術者と打ち合わせを通して、既製品のセンサーを地磁気計測に適したものとなるような改良を加えた。改良点は、(1)計測レンジの±80000 nTへの拡大、(2)パルス信号生成素子のセンサー基盤への搭載、(3)基盤のサイズを調整、の3点である。センサーを固定するための治具や、アナログ-デジタル変換器、Raspberry Piを使ったデータを記録するためのロガー、Pythonを使ったデータ表示プログラム、などを自作し、改良したセンサーと組み合わせて、観測システムのプロトタイプを完成させた。そのため、観測システム一式の製作価格は数十万円ほどである。そのシステムを用いて、愛知県豊川市や豊田市でテスト計測を行い、Sq変動や地磁気脈動など、自然の地磁気変動現象が問題なく観測できることを確認した。システムの詳細や計測結果は、学会や研究会などで発表した。
    MIセンサーは、地上で地磁気観測を行うために開発・改良をはじめたものであるが、幸運なことに科学観測ロケット(LAMPロケット)に搭載し高度300-400 kmにおける磁場計測を行える機会が得られたため、そのロケットプロジェクトへの参加も同時に進行している。ロケットプロジェクトの研究者と連絡を取り合いながら、ロケット搭載のためにセンサー冶具、データ取得およびロケット共通バスとのやり取りを行う回路部分の設計や製作を行い、打ち上げ前の実験室でのテスト計測を行っている。
    既製品の時期インピーダンスセンサーを、主磁場が大きい高緯度でも計測できるように計測レンジを広げたり、フィールドで用いることを前提に電子回路基板の枚数を減らしたり、というように地磁気計測に適したものに改良した。その後、地磁気3成分を取得できるように、3枚の基板を異なる方向に固定できるような治具を製作し、改良したセンサーを取り付けた。センサーの計測結果はアナログ信号として出力されるので、市販の手ごろな価格で手に入るアナログ-デジタル変換器を選定し、デジタル信号に変換した後、Raspberry Piを用いたデータロガーに取り込んで記録するようなシステムのプロトタイプを開発した。このプロトタイプシステムを用いて、2019年6月29日から7月3日に愛知県豊川市において、2020年2月13日から2月20日に愛知県豊田市において、実際に地磁気のフィールド計測を行った。地磁気の一日変動や、周期1-2分程度の地磁気脈動が計測できていることが確認できた。
    さらには、科学観測ロケットへの搭載機会を得たため、搭載センサーコンポーネントおよび機上データ処理コンポーネントを製作し、その間のデータやり取りなどのテストなどを行った。
    当初の目的であった、安価な地磁気観測システムの製作に関しては、プロトタイプ製作やそれを用いたフィールド観測実施など、十分な成果が得られた。ただ、温度によって計測値が大きく変化する温度ドリフトの効果や、治具の製作精度やセンサーの取り付け精度に伴う計測軸の非直交度については、引き続き改良および較正する必要があると考えている。また、数日だけの計測ではなく、数年にわたるフィールド計測を行い、長期間のデータ取得とその評価を行うことが求められる。
    現時点では、LAMPロケットの打ち上げは2021年初旬に予定されているので、MIセンサー搭載に向けての準備や、その後のデータ解析を行うつもりである。

  5. 磁気リップル現象の生成機構解明と短周期大気波動の全球的モニタリングへの応用

    研究課題/研究課題番号:17K05669  2017年4月 - 2021年3月

    家森 俊彦

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    担当区分:研究分担者 

    ・ESAからSwarm電子密度観測データを収集・処理し、蓄積すると共に、磁場データと比較した。ハイパスフィルターをかけると、電子密度データにも磁場の場合と同様に、小規模な波動状構造が頻繁に見られることがわかった。しかし、磁場変動(磁気リップル)と電子密度変動(電子密度波状構造)は、軌道に沿って観測される見かけの周期が異なり、振幅が極大となる場所も必ずしも一致しない。また、磁気リップルは電離層電気伝導度に比例して昼間側の振幅が大きいが、電子密度波状構造は夜間の方が振幅が大きい。
    ・昨年度は、音波モードの大気波動が鉛直上方に伝搬、電離圏E層でダイナモ電流を流し、それが沿磁力線電流として衛星軌道まで流れ、磁気リップルとして観測されると共に、鉛直上方に伝搬した音波が衛星軌道の電離圏F層で電子密度擾乱を起こしていると解釈すると、衛星軌道上での磁場変動と電子密度変動の位置関係が矛盾なく説明できる例をいくつか見いだした。今年度は、この解釈が一般的に成り立つか否かを確認するため解析例を増やした。また、電子密度変動のグローバルな分布を求め、磁場変動のグローバル分布と比較した。その結果、一定の類似性が見られるが、かなり相違する領域もあることが判明した。
    ・タイ・ピマーイで取得した微気圧、磁場、降雨およびGPS-TEC データから、スコール発生時の微気圧変動と電離圏TECおよび磁場変動の関連を前年度に引き続き調べた。
    ・トカラ・中之島で行っていた微気圧計、磁力計、高時間分解能の雨量計による観測を6月まで継続したのち、機器を撤去した。2013年から開始した観測データは全て毎秒値ファイルの形でデータベース化した。2017年以降のGPS観測データ(15秒値)を入手した。
    ・地上観測データを公開することに役立つと考えられる京都大学内のデータマネージメントシステム開発を目指す活動に参画した。
    (1)Swarm衛星による磁場および電子密度データの取得を継続すると共に、微気圧変動や磁場、GPS-TECなどの地上観測データを蓄積することができた。
    (2)電子密度データに、これまで報告されていない微細な波状構造がほぼ常時存在することを見いだした。
    (3)Swarm電子密度データの統計的解析を行い、グローバルな分布およびそれらの季節依存性等を調べることにより、これまで行ってきた磁場変動のグローバル分布の特性と比較することができた。
    (4)地上観測データを蓄積することにより、観測諸量の関連を調べることのできるイベント数を大幅に増やすことができた。
    ・学会で発表を行った成果を論文として学術誌に公表することが遅れているので、それを最優先する。
    ・自らが観測・取得した地上観測データについては、その整理と公開のためのデータベース化を行う。
    ・地上観測データとSwarm衛星観測データの同時観測例を更に多く解析することにより、下層大気擾乱の磁気リップル現象および電子密度波状構造生成における役割と、現在推測しているそれらの生成メカニズム、すなわち、「大気音波モード重力波による電離層でのダイナモ効果と、波動の電離圏F層への伝搬」を更に確かなものとする。
    ・下層大気擾乱の一つである積雲対流の強度の指標として有用と考えられるグローバルな降雨分布データが昨年度から公開されたので、それも解析に利用することにより、磁気リップル現象および電子密度波状構造のグローバル分布の成因の理解を深める。

  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

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    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. 衛星多点観測と計算機シミュレーションによる内部磁気圏のイオン組成変化要因の探究

    研究課題/研究課題番号:16H04057  2016年4月 - 2019年3月

    能勢 正仁

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    担当区分:研究代表者 

    配分額:14560000円 ( 直接経費:11200000円 、 間接経費:3360000円 )

    日本が2016年12月にうちあげた「あらせ衛星」の観測データの解析および計算機シミュレーションにより、酸素イオントーラスおよびイオンと長周期地磁気脈動のドリフトバウンス共鳴現象に関する研究を行った。酸素イオントーラスに関しては、その形状が軸対象ではなく朝側に偏った三日月形であることが、世界で初めて明らかにされた。ドリフトバウンス共鳴がリングカレントのエネルギー増加に少なからぬ影響を及ぼしていることやそれにはイオン種依存性があること、イオンフラックスの空間勾配が共鳴の重要なパラメターになり得ること、などの新しい発見が得られた。以上の研究成果を含め、査読付き国際学術誌に25編の論文を出版した。
    日本が打ち上げた国産の「あらせ衛星」が観測したデータに基づく研究成果であるため、日本発の科学成果を世界に向けて発信することができた。酸素イオントーラスの経度方向の構造が軸対象ではなく朝側に偏っていること、およびドリフトバウンス共鳴がリングカレントの発達に効果的であることやそのイオン種依存性などは、これまでに報告のなされたことのないもので、学術的に大きな意義のある発見である。人類が宇宙空間を利用していくに当たって宇宙天気予報の研究が進んでおり、その実用化のために理解すべき、宇宙空間におけるイオンのダイナミクスの一端を明らかにした点で社会的な意義があると考えている。

  8. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:16HP8026  2016年4月 - 2017年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    資金種別:競争的資金

    配分額:1700000円

  9. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:15HP8028  2015年4月 - 2016年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:1600000円

  10. 深内部磁気圏における高エネルギーイオン生成・輸送機構とそのイオン種依存性の解明(国際共同研究強化)

    研究課題/研究課題番号:15KK0161  2015年

    国際共同研究加速基金(国際共同研究強化)

    能勢 正仁

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    担当区分:研究代表者 

    配分額:14300000円 ( 直接経費:11000000円 、 間接経費:3300000円 )

  11. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:268023  2014年4月 - 2015年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    資金種別:競争的資金

    配分額:2300000円

  12. 下層大気の大規模擾乱に起因する超高層電磁場変動の解明とその応用研究

    研究課題/研究課題番号:25287128  2013年4月 - 2016年3月

    家森 俊彦

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    担当区分:研究分担者 

    低高度精密磁場観測衛星が、中低緯度電離圏でほぼ常時観測する微細な磁場変動(magnetic ripplesと命名)は、これまでその存在すら認識されていなかった微細な沿磁力線電流の空間構造であることを世界で初めて明らかにした。また、それらの振幅の季節・地方時・緯度依存性や変動の時間スケールなどを求めた。地理的依存性や地震・火山噴火時に地上で観測される磁場、微気圧およびGPS-TEC変動も考慮することにより、それらが、下層大気の擾乱を起源とし、電離圏まで伝搬した重力音波が、電離層でのダイナモ作用を介して電離層に電流を流し、それが磁力線に沿って発散し沿磁力線電流になっていることを明らかにした。

  13. 深内部磁気圏における高エネルギーイオン生成・輸送機構とそのイオン種依存性の解明

    研究課題/研究課題番号:25287127  2013年4月 - 2016年3月

    能勢 正仁

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    担当区分:研究代表者 

    配分額:12740000円 ( 直接経費:9800000円 、 間接経費:2940000円 )

    気象衛星ひまわりやGPS衛星が飛翔する地球周辺の宇宙空間(内部磁気圏)は、荷電粒子からなるプラズマで満たされている。内部磁気圏のプラズマは、平時は水素イオンが主成分であるが、磁気嵐が起こると酸素イオンの含有量が急激に増加する。この研究では、内部磁気圏を観測している科学衛星のデータを解析し、その原因の究明を行った。その結果、「電離層から内部磁気圏へ酸素イオンが直接流出しており、それが磁場双極子化に伴う微小磁場擾乱によりその場で選択的に加速される」ためであることが明らかになった。

  14. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:248032  2012年4月 - 2013年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    資金種別:競争的資金

    配分額:2200000円

  15. サブストームトリガー・駆動機構の完全解明に向けた先端研究

    研究課題/研究課題番号:22340145  2010年 - 2012年

    町田 忍

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    担当区分:研究分担者 

    サブストームは地球磁気圏・電離圏で発生する大規模なエネルギー解放現象であるが、そのトリガー機構と駆動機構の解明を目指して、衛星および地上同時観測で得られた最新データを用いて研究を実施した。その結果、われわれがかねてより提案しているサブストームのトリガー・駆動機構モデルの正当性を確認することができた。また、サブストームに関連したオーロラ電波放射(AKR)について幾つかの重要な知見を得た。

  16. 地上・衛星の多点観測データを用いた深内部磁気圏擾乱の発達・減衰に関する総合解析

    研究課題/研究課題番号:22740322  2010年 - 2012年

    能勢 正仁

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    担当区分:研究代表者 

    配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

    磁気圏擾乱の指標であるDst指数には、リングカレントなどの磁気圏電流と地球内部に誘起された電流の寄与が混在している。これまで、地球内部誘起電流の寄与は約25%で一定と考えられてきたが、今回の研究により、その割合は20%から55%の間で変化し、Dst指数の時間変化率と高い相関を持つことが明らかになった。また、リングカレントの発達に関しては、過去に報告されてきたような「プラズマシートからの高エネルギー粒子の流入」よりも、「その場に既に存在していた低エネルギー粒子が短周期の磁場擾乱によって受けるローカルな非断熱的加速」がより重要な役割を果たしていることが分かった。

  17. 地球惑星科学仮想データセンターの構築と機能の実証的研究

    研究課題/研究課題番号:20244081  2008年 - 2010年

    家森 俊彦

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    担当区分:研究分担者 

    大小様々な組織が提供する地球惑星科学関係のデータベースを、メタデータのデータベースを核として、サイバースペースで結合し、異分野横断・学際研究推進の母体となる『地球惑星科学仮想データセンター』創出の実現可能性を実証的に研究した。実施にあたっては、大学間連携プロジェクト『超高層大気長期変動の全球地上ネットワーク観測・研究』(IUGONET)と密接に協力し、使用するメタ情報フォーマットを検討、SPASE data modelが最適であると判断した。IUGONETと協力してシステムを開発し、微気圧観測データと地磁気データを具体例として、メタデータの入力およびデータベースの構築を実施した。

  18. 下層大気の大規模擾乱に起因する宇宙空間電磁気現象の研究

    研究課題/研究課題番号:19654073  2007年 - 2008年

    萌芽研究

    家森 俊彦

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    担当区分:研究分担者 

    当研究は、地震や火山噴火、台風など地球表面付近の現象が、それより上層の海洋、大気の運動を通して、電離圏や磁気圏に電磁気学的現象を発生させるメカニズムの理論的考察と、観測および数値シミュレーションによる検証を全体構想とする。本年度は、下記の成果が得られた。
    1. 平成18年夏から観測を開始した微気圧観測データと、近接地点の地磁気観測データを統計的に解析することにより、理論的に予想されてきた3つの周波数帯に、気圧、磁場ともスペクトル密度ピークが存在することを、データを増やすことにより、統計的により確実にすることができた。また、微気圧振動のピークは秋に明瞭に見られるという前年度示唆された結果をより確実なものにした。
    2. 平成20年度は微気圧観測システムをペルーのアンコン観測所に設置した。このデータは、磁場観測データと共に昨年末から京都大学に転送されており、解析を進めつつある。
    3. 2004年12月のスマトラ地震時に、中国南部で観測された約20秒余りの周期の地磁気脈動が、その場所での磁力線共鳴周期とほぼ一致すること、また、それ以外の場所では見られないことを、それぞれ、理論的計算およびデータ解析から確認した。このことは、この約20秒余りの周期の地磁気脈動が、スマトラ地震によって引き起こされた磁力線共鳴現象であることを強く示唆し、下層大気の大規模擾乱に起因する宇宙空間電磁気現象の一つであることを示す。
    4. 研究協力者と共に、数値シミュレーションで確認するための計算コードの3次元化に着手した。

  19. 複数衛星観測による深内部磁気圏の磁場構造変化とイオン組成変化に関する研究

    研究課題/研究課題番号:19740303  2007年 - 2008年

    能勢 正仁

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    担当区分:研究代表者 

    配分額:3520000円 ( 直接経費:3100000円 、 間接経費:420000円 )

    これまでは、静止衛星軌道より内側のリングカレント領域(高度20000-30000km付近)の磁場構造はそれほど大きく変化しないと考えられることが多く、双極子磁場による近似が行われてきた。しかしながら、MDS-1衛星の磁場観測により、このような領域でもサブストームに伴う磁場双極子化や高周波の磁場擾乱が現れたり、磁場構造が強く引き伸ばされた形状になったりするように、内部磁気圏の磁場構造は想像以上に変動していることが明らかになった。こうした磁場変動は、特に酸素イオンを選択的に加速し、リングカレントのイオン組成変化に重要な役割を果たしていることが分かった。

  20. リモートセンシングによる磁気圏・極域電離圏プラズマの動態の解明

    研究課題/研究課題番号:18540443  2006年 - 2008年

    田口 聡

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    担当区分:研究分担者 

    地球の周辺の宇宙空間には電気を帯びた微粒子が存在しており, 様々な場所でそれぞれ固有の速さで動いている. 本研究では, その微粒子の一部が姿を変えた中性の粒子の運動を検出する撮像のデータを主に用いて, 電気を帯びた微粒子であるイオンの太陽風から磁気圏への直接的な流入, 地球磁気圏の外壁であるマグネトポーズの運動, 電離圏から磁気圏へと上昇するイオンの流れに関して, これまでに知られていない性質を見出した.

  21. ユーラシア大陸横断磁力計列構築と精密衛星磁場観測に基づく自然電磁環境変動の研究

    研究課題/研究課題番号:17403008  2005年 - 2007年

    家森 俊彦

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    担当区分:研究分担者 

    地磁気は超高層物理学および地球内部電磁気学的研究にとって最も基礎的で重要な物理量であり、汎世界的に分布する観測所で長期間安定した測定をする必要がある。当研究では、地磁気ディジタルデータの巨大な空白地帯となっているシルクロード沿いおよびその延長線上の地域に存在する約12ヶ所の地磁気観測所のうち3ヶ所に、高精度ディジタル磁力計を設置し、中緯度のユーラシア大陸を横断する長大な磁力計ネットワークを構築することを計画し実施した。そして、上記ネットワークで取得されたデータとOersted精密磁場観測衛星等のデータを用いて、地磁気脈動の東西伝搬、オーロラ帯に流れ込む沿磁力線電流の刻々の時間変化の推定、電離層ダイナモ電流の逐日および経度依存変動やその原因となる下部電離層の中性風の推定、磁気圏サブストーム開始の指標となるPi2型地磁気脈動のリアルタイム検出等、このネットワークの特徴を生かした超高層物理学的研究を推進した。また、トルコ、中央アジアなど、地殻活動の活発なシルクロード沿いの地球内部電磁気学的諸観測にとって基準となる高精度・高時間分解能地磁気データを提供することも、目的の一つとした。Pi2型地磁気脈動のリアルタイム検出結果は京都大学大学院理学研究科地磁気世界資料解析センターのホームページから公開した。(URL:http://swdcli40.kugi.kyoto-u.ac.jp/pi2/)また、トルコおよびインドからの観測データ(毎分値および毎秒値)は、電話回線およびインターネットを経由して、準リアルタイムで京都に送られている。

  22. 汎地球的地磁気観測によるPi2地磁気脈動リアルタイム検出システムの構築

    研究課題/研究課題番号:17740327  2005年 - 2006年

    能勢 正仁

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    担当区分:研究代表者 

    配分額:3500000円 ( 直接経費:3500000円 )

    2005年7月から9月にかけて、イギリス(ランカスター大学)、ドイツ(フルステンフェルドブルク観測所)・アメリカ(ジョンズホプキンス大学応用物理研究所)・メキシコ(テオロユーカン観測所)、日本(柿岡地磁気観測所、峰山観測所)の合計6観測所を順次訪問し、ウェーブレット解析を使ってPi2地磁気脈動を自動検出するソフトウェアをインストールした。Pi2地磁気脈動が検出されると、その波形や検出時刻などの結果は、電子メールで申請者の所属する京都大学へ送られ、WWWで公開されるようになっている。各観測所では、地磁気データをリアルタイムで収集しているので、検出結果もほぼリアルタイムでWWWから見られるようになっている。WWWアドレスは、http://swdcli40.kugi.kyoto-u.ac.jpである。また、このようなデータ収集で得られた経験を基にして、サブストームの発生を中低緯度の地磁気観測から推定するための新しい地磁気指数を考案し、その算出を行い始めた。この新しい指数をAE指数や静止軌道衛星の粒子フラックスと比較し、それぞれの間に比較的よい相関があることが分かった。その他に、柿岡地磁気観測所とHermanus地磁気観測所のデータを用いて、Pi2地磁気脈動の経度方向の構造を統計的に調べた結果、その経度方向の波数はほぼ0に近い値となり、全球的に同位相で振動が起こっていることが明らかになった。
    以上の研究内容・活動を国内外の学会で5回(国内3回・国外2回)にわたって報告を行った。研究成果は、Nose et al.,Earth Planet.Space,58,775-783,2006とNose et al.,Proceedings of the Eighth International Conference on Substorms(ICS-8),209-214,2006の2つの学術論文として発表した。加えて、関連した研究として主著論文1編、共著論文2編を発表した。

  23. マグネトグラム古記録の数値化技術の開発とそれを用いた太陽風長期変動の研究

    研究課題/研究課題番号:16654076  2004年 - 2005年

    萌芽研究

    家森 俊彦

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    担当区分:研究分担者 

    (1)古いマグネトグラム記録をディジタル画像ファイル化する作業およびその画像を処理してデータベース化する手順の効率化を進めた。
    (2)データベース化した処理済みの画像ファイルをwebから公開した。(http://swdcft49.kugi.kyoto-u.ac.jp/film/index-j.html)
    (3)磁気圏境界面での速度シアーによるケルビンヘルムホルツ型不安定性が主要な発生メカニズムであるため、太陽風速度と関係があるPc5型地磁気脈動の性質を用いて、太陽風観測データのない1960年以前の地磁気観測データから太陽風速度を推定することを目的の一つにした。そのために、まず、太陽風速度とPc5型地磁気脈動の振幅の関係を調べた。その結果、600km/s以上の高速太陽風の場合も、太陽風速度と脈動の振幅の間の正相関の関係は、600km/s以下の場合の延長上にあることがわかった。また、Pc5型地磁気脈動の発生には、太陽風密度の変動が影響していることを示唆する結果が得られた。
    (4)2次元画像処理手法を用いて連続なグラフ部分のみを取り出す試みを行った。
    (5)2005年11月に英国エディンバラで開催されたディジタルデータ保存に関する国際会議PV2005に家森が出席し、当研究の成果の一部を発表した。
    (6)ディジタル画像化されたデータを用いて、1960年のチリ大地震の時の世界各地の地磁気変化を調べた。その結果、震源から遠く離れたヨーロッパやアフリカでも地震波による磁力計の振動の影響が出ていること、また、イースター島では、津波の通過したと考えられる時刻に、津波による海洋ダイナモ電流が原因と考えられる地磁気変化が観測されていたことがわかった。この結果は、2006年5月の日本地球惑星科学連合2006年大会で発表を予定している。

  24. 人工衛星塔載型磁力計方式での地上観測所3成分絶対磁場測定装置の試験研究

    研究課題/研究課題番号:16540406  2004年 - 2005年

    亀井 豊永

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    担当区分:研究分担者 

    平成17年度は非常に残念ながら研究代表者の病状悪化のため年度の延期を打診したが、だめだった。このため、1つの試作機を完成するのではなく、いろいろな部分性能評価を重視することとした。平成16年度で作成した、非磁性セオドライトの回転部分は磁場測定は1分1回転で予定通り1/30秒毎のAD測定に耐える、また、星座からの角度確定では、広角で角度1度以内から10分程度でに決められるがその磁場測定とのタイミングあわせは非常に難しい。望遠鏡を使用した侠角1分精度で星座を探すためには非常に高速のCPUが必要となり回転が安定しないと仮定した地上装置とノートPCではやはり無理がある。そのため、2つの予定外の方法を試すことにした。1つは値下がりした民生用ハイビジョンカメラと非常に高速のCPUと2GB高速大メモリーを備えたデスクトップPCを試した、しかしこれは非圧縮DVカメラ(3色約15MHz固定)と違い画像が25MHzMPEG圧縮のため画像が非常に荒く、しかも時間遅れが不安定で0,3-0.7秒遅れでPCに送り込まれるためHDV信号や圧縮デジタル機能を使用するのはこの角度測定用途にむかず、単純にHDVのアナログD3信号を直接ベースバンド(3色約150MHz)で映像取り込みして処理する必要がある。もう1つの方法は、余り早く回転させるとどのような狭角測定法でも無理がでるので、回転軸方向に侠角は星座判定をする方法にすることである。このためには望遠鏡方向に邪魔がないようにセオドライトの幾何学的配置を見直しセオドライトの支柱が望遠鏡とカメラを避けるように設計を工失する。なお、十分テストは出来ていないが、回転上の複数の星が明らかになった状態で複数の視野に連続に入ってくる明るい星や昼間の太陽タイミングを狙う場合にはやはり圧縮HDV信号は無理でD3信号を基準にHDVのベースバンドの信号を使用して角度の秒単位での角度測定は実用になると考える。このほかの、セオドライトの180度自動回転や気象条件や耐久性を試すテストは更に後ほど行うことになる。

  25. 非対称磁気圏構造形成の物理とモデル化

    研究課題/研究課題番号:13640451  2001年 - 2002年

    家森 俊彦

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    担当区分:研究分担者 

    (1)エールステッド衛星による最新の観測データを、ネットワークを用いてデンマーク気象研究所から転送しワークステーション上にデータベース化した。(2)磁場観測データを解析するためのソフトウェアを作成した。ソフトウェアは、過去の研究過程で作成されたプログラムを改良・移植するほか、新たに内部磁気圏電流モデルとそれによる地上磁場変化を計算するソフトウェアを作成した。(3)これまでに蓄積された人工衛星磁場観測データのうち、DE-1衛星磁場観測データを解析し、磁場・電流構造を定量的に解析した。(4)地上磁場データから沿磁力線電流を推定した。(5)家森と荒木、能勢がH13年8月にハノイで開催されたIAGA-IASPEI合同科学大会に参加し、これまでの研究結果を発表した。
    (6)中低緯度におけるエールステッド衛星磁場観測データから、極域電離層に出入りする"net field-aligned current"の地方時分布を求めた。その結果、正午前に流入し、真夜中前から流出していることが確認された。(7)DE-1衛星磁場観測データ解析からも、昼間側から流入し、夜側から流出する"net field-aligned current"の存在を確認することができた。(8)電離層レベルでの電流構造と物理を今後更に詳細に調べるために、SuperDARN極域HFレーダーデータの整備を行った。(9)平成14年9月にデンマークで開催された第4回エールステッド科学会議に家森が出席し、上記成果を発表した。平成15年4月のEGS-AGU-EUG合同会議にも家森が出席し発表した。

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担当経験のある科目 (本学) 6

  1. 物理学実験

    2020

  2. 宇宙電磁観測セミナー2A-2E

    2020

  3. 卒業研究B

    2020

  4. 卒業研究A

    2020

  5. 宇宙電磁観測セミナー1A-1D

    2020

  6. データ解析処理論

    2020

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