日本地球惑星科学連合2018年大会

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[EE] Eveningポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM15] Dynamics in magnetosphere and ionosphere

2018年5月21日(月) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:田中 良昌(国立極地研究所)、堀 智昭(名古屋大学宇宙地球環境研究所)、中溝 葵(情報通信研究機構 電磁波研究所、共同)、尾崎 光紀(金沢大学理工研究域電子情報学系)

[PEM15-P12] Energetic electron precipitations during magnetic storms of 7-8 September, 2017 using LF/VLF standard radio waves

*宮下 拓也1大矢 浩代1土屋 史紀2塩川 和夫3三好 由純3中田 裕之1鷹野 敏明1 (1.千葉大学、2.東北大学、3.名古屋大学)

キーワード:磁気嵐、高エネルギー電子の降り込み

During geomagnetic storms, a lot of studies have been reported energetic electrons precipitate into the atmosphere at the high latitudes. It is known that the low-latitude limit of the particle precipitations is L ~ 4.0 (Berkey et al., 1974). However, several studies reported that the particle precipitations occurred at the mid and low latitudes (L ~ 1.3-2.8) (Kikuchi and Evans, 1989; Clilverd et al., 2008). In this study, we investigate the precipitations of energetic electrons into the atmospheres during the geomagnetic storms of 7-8 September, 2017, using a network of LF/VLF standard radio waves from the low and high latitudes. The transmitters are NRK (Iceland, 37.5 kHz), NPM (Hawaii, 21.4 kHz), and JJI (Japan, 22.2 kHz), while the receivers are NYA (Ny-Alesund, L = 15.55) and PKR (Poker Flat, L = 5.95). The geomagnetic storms occurred on 7-8 September, 2017. The minimum Dst value was -142 nT at 02:00 UT on 8 September, 2017. A substorm onset was 19:40 UT on 7 September, 2017. On the NRK-NYA propagation path (the path length: 2002.2 km, night propagation), variations in the LF intensity and phase due to precipitations were seen from 23:20 UT on 7 September to 01:00 UT on 8 September. The amplitudes of the variations in the intensity and phase were about 7 dB and 70 degrees, respectively. Based on wavelet spectra, the NRK-NYA intensity and phase had periods of 10 min. and 30-40 min. The periods of 10 min. would correspond to Pc5 modulation. At the mid-point of the NRK-NYA path (jan: Jan Mayen, Norway), magnetic D component had similar period of 30-40 min. during the LF variations, while the H and Z components had 50-80 min. Similarly, on the NRK-PKR path (4999.0 km, night-day propagation), variations in intensity and phase were seen from 23:24 UT on 7 September to 01:00 UT on 8 September. The amplitudes of the intensity and phase were about 4 dB and 40 degrees, respectively. The periods of the intensity and phase were same (10 min. and 30-40 min.) with those of the NRK-NYA path. At the mid-point of the NRK-PKR path (thl: Qaanaaq, Greenland), magnetic H, D, and Z components had 30-80 min. In the presentation, we will show LF/VLF variations on other paths of NPM-NYA and JJI-NYA in more detail.