研究者詳細 - 家田　章正

論文 - 家田　章正

分割表示 56 件中 1 - 20 件目／全件表示 >>

Duskward displacement of plasmoids and reconnection in the near-Earth magnetotail 査読有り

Ieda Akimasa, Miyashita Yukinaga

EARTH PLANETS AND SPACE 76 巻 2024年12月

地球電離圏の電荷交換衝突におけるカーブ軌道効果査読有り

Ieda, A.

Journal of Geophysical Research: Space Physics 2022年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

電離圏と磁気圏の結合を理解するためには、電離圏電気伝導度を定量的に把握することが必要である。電気伝導度の主体は、イオンと中性粒子の衝突断面積である。この断面積は、２つの成分を持つが両成分の和ではなく、高温では電荷交換成分に、低温では中性粒子の分極による成分に漸近する。両成分が等しくなる遷移温度は、電離圏温度（200-2000 K）付近である。これまで電離圏分野の古典的研究では、遷移温度において、トータルの衝突断面積は、分極成分や電荷交換成分に等しいと近似されてきた。すなわち、両成分は結合しないと仮定されてきた。一方、原子衝突分野の研究では、トータルの断面積は、電離圏の古典的研究よりも1.4倍大きいと近似されている。この電離圏分野と原子衝突分野の違いの根拠は不明瞭であった。

本研究では、電荷交換衝突と分極衝突の結合を、カーブ粒子軌道効果により表現した。すなわち、粒子軌道が曲がることにより電荷交換衝突断面積が実効的に増大する効果を取り入れた。その結果、遷移温度において、トータルの断面積は、電荷交換成分から22%増大することを見いだした。原子衝突分野では、この結合を物理的意味のない二乗平均により表現したために過大評価している。電離圏分野の古典的研究がこの結合を無視した原因は、カーブ粒子軌道効果と、外部境界付近をかすめる軌道の小さい効果とを、混同したことであると思われる。もうひとつの原因は、結合を表現する理論式がなかったためであると思われる。その様な理論式は本研究で初めて導いたので、今後は電荷交換衝突と分極衝突の結合を無視せずに含めて、イオン-中性衝突断面積を計算すれば良い。

DOI： 10.1029/2020JA028441

Atomic Oxygen Ion‐Neutral Collision Frequency Models at Ionospheric Temperatures 査読有り

Ieda, A.

Journal of Geophysical Research: Space Physics 2021年1月

Ion-Neutral Collision Frequencies for Calculating Ionospheric Conductivity 査読有り

Ieda A.

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

Location and Timing of Magnetic Reconnections in Earth's Magnetotail: Accomplishments of the 29-Year Geotail Near- Earth Magnetotail Survey 査読有り国際共著

Nagai, T., Shinohara, I., Saito, Y., Ieda, A., & Nakamura, R.

Journal of Geophysical Research: Space Physics 128 巻 2023年12月

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 2018年5月

Stepwise tailward retreat of magnetic reconnection: THEMIS observations 査読有り

Ieda, A. , Y. Nishimura, Y. Miyashita, V. Angelopoulos, A. Runov, T. Nagai, H. U. Frey, D. H. Fairfield, J. A. Slavin, H. Vanhämaki, H. Uchino, R. Fujii, Y. Miyoshi, and S. Machida

J. Geophys. Res. Space Physics 121 巻頁： 4548-4568 2016年5月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Auroral stepwise poleward expansions were clarified by investigating a multiple-onset substorm that occurred on 27 February 2009. Five successive auroral brightenings were identified in all-sky images, occurring at approximately 10 min intervals. The first brightening was a faint precursor. The second brightening had a wide longitude; thus, it represented the Akasofu substorm onset. Other brightenings expanded poleward; thus, they were interpreted to be auroral breakups. These breakups occurred stepwise; that is, later breakups were initiated at higher latitudes. Corresponding reconnection signatures were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations from between 8 and 24 Re down the magnetotail. The Akasofu substorm onset was not accompanied by a clear reconnection signature in the tail. In contrast, the three subsequent auroral breakups occurred simultaneously (within a few min) with three successive fast flows at 24 Re; thus, these were interpreted to be associated with impulsive reconnection episodes. These three fast flows consisted of a tailward flow and two subsequent earthward flows. The flow reversal at the second breakup indicated that a tailward retreat of the near-Earth reconnection site occurred during the substorm expansion phase. In addition, the earthward flow at the third breakup was consistent with the classic tailward retreat near the end of the expansion phase; therefore, the tailward retreat is likely to have occurred in a stepwise manner. We interpreted the stepwise characteristics of the tailward retreat and poleward expansion to be potentially associated by a stepwise magnetic flux pile-up.

DOI： 10.1002/2015JA022244

Approximate forms of daytime ionospheric conductance 査読有り

Ieda, A., S. Oyama, H. Vanhamäki, R. Fujii, A. Nakamizo, O. Amm, T. Hori, M. Takeda, G. Ueno, A. Yoshikawa, R. J. Redmon, W. F. Denig, Y. Kamide, and N. Nishitani

J. Geophys. Res. 119 巻 2014年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The solar zenith angle (SZA) dependence of the conductance is studied and a simple theoretical form for the Hall-to-Pedersen conductance ratio is developed, using the peak plasma production height. The European Incoherent Scatter (EISCAT) radar observations at Tromso (67 MLAT) on 30 March 2012 were used to calculate the conductance. The daytime electric conductance is associated with plasma created by solar extreme ultraviolet radiation incident on the neutral atmosphere of the Earth. However, it has been uncertain whether previous conductance models are consistent with the ideal Chapman theory for such plasma productions. We found that the SZA dependence of the conductance is consistent with the Chapman theory after simple modifications. The Pedersen conductance can be understood by approximating the plasma density height profile as being flat in the topside E region, and by taking into account the upward gradient of atmospheric temperature. An additional consideration is necessary for the Hall conductance, which decreases with increasing SZA more rapidly than the Pedersen conductance. This rapid decrease is presumably caused by a thinning of the Hall conductivity layer from noon towards nighttime. We expressed this thinning in terms of the peak production height in the Chapman theory.

DOI： 10.1002/2014JA020665

A Statistical Study of Near-Earth Magnetotail Evolution During Pseudosubstorms and Substorms With THEMIS Data

Fukui Kento, Miyashita Yukinaga, Machida Shinobu, Miyoshi Yoshizumi, Ieda Akimasa, Nishimura Yukitoshi, Angelopoulos Vassilis

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 125 巻 ( 1 ) 2020年1月

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

EARTH PLANETS AND SPACE 71 巻 2019年7月

Revisiting substorm events with preonset aurora

Miyashita Yukinaga, Ieda Akimasa

ANNALES GEOPHYSICAE 36 巻 ( 5 ) 頁： 1419-1438 2018年10月

Theory, modeling, and integrated studies in the Arase (ERG) project

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 2018年2月

Visualization tool for three-dimensional plasma velocity distributions (ISEE_3D) as a plug-in for SPEDAS

Keika Kunihiro, Miyoshi Yoshizumi, Machida Shinobu, Ieda Akimasa, Seki Kanako, Hori Tomoaki, Miyashita Yukinaga, Shoji Masafumi, Shinohara Iku, Angelopoulos Vassilis, Lewis Jim W., Flores Aaron

EARTH PLANETS AND SPACE 69 巻 2017年12月

A direct link between chorus emissions and pulsating aurora on timescales from milliseconds to minutes: A case study at subauroral latitudes 査読有り

Ozaki, M., S. Yagitani, K. Sawai, K. Shiokawa, Y. Miyoshi, R. Kataoka, A. Ieda, Y. Ebihara, M. Connors, I. Schofield

J. Geophys. Res. Space Physics 120 巻頁： 9617-9631 2015年11月

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., Y. Miyashita, A. Ieda, M. Nosé, V. Angelopoulos, and J. P. McFadden

Ann. Geophys. 32 巻頁： 99–111 2014年2月

Ground-based ELF/VLF chorus observations at subauroral latitudes - VLF-CHAIN Campaign 査読有り

Shiokawa, K., Y. Yokoyama, A. Ieda, Y. Miyoshi, R. Nomura, S. Lee, N. Sunagawa, Y. Miyashita, M. Ozaki, K. Ishizaka, S. Yagitani, R. Kataoka, F. Tsuchiya, I. Schofield, and M. Connors

J. Geophys. Res. 119 巻 2014年

General solution for calculating polarization electric fields in the auroral ionosphere and application examples 査読有り

Amm, O., R. Fujii, H. Vanhamäki, A. Yoshikawa, and A. Ieda

J. Geophys. Res. 118 巻頁： A11217 2013年5月

An application of the finite length Cowling channel model to auroral arcs with longitudinal variations 査読有り

Fujii, R., O. Amm, H. Vanhamäki, A. Yoshikawa, and A. Ieda

J. Geophys. Res. 117 巻頁： A11217 2012年11月

Observed correlation between pulsating aurora and chorus waves at Syowa Station in Antarctica 査読有り

Ozaki, M., S. Yagitani, K. Ishizaka, K. Shiokawa, Y. Miyoshi, A. Kadokura, H. Yamagishi, R. Kataoka, A. Ieda, Y. Ebihara, N. Sato, and I. Nagano

J. Geophys. Res. 117 巻頁： A08211 2012年

Rayleigh-Taylor type instability in auroral patches 査読有り

Shiokawa, K., A. Nakajima, A. Ieda, K. Sakaguchi, R. Nomura, T. Aslaksen,M. Greffen, and E. Donovan

J. Geophys. Res. 115 巻頁： A02211, doi:10.1029/2009JA014273 2010年2月

　前のページ - 次のページ　

<家田 章正>

論文 - 家田 章正

<家田　章正>

論文 - 家田　章正