日本地球惑星科学連合2018年大会

講演情報

[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-P09] Nightside Ultra-Low-Frequency waves observed in the topside ionosphere by the DEMETER satellite

*Xinyan Ouyang1 (1.Institute of Earthquake Forecasting, China Earthquake Administration)

キーワード:topside ionosphere, ultra-low-frequency oscillations, electron density perturbations

We study Ultra-Low-Frequency waves (ULF) at frequencies 17-100 mHz observed in the topside ionosphere by the DEMETER satellite in a ~5-year period from January 2006 to November 2010. Our results show that two types of ULF oscillations occur on the nightside in the L<2 region. These two kinds of ULF oscillations are separated based on cross-covariance analysis between electric field in the DC/ULF range and electron density. Type I ULF oscillations, accompanied by electron density perturbations (average |δNe/Ne0|>5%), are found to lag behind density variations; and the longitudinal distribution of type I ULF oscillations is quite similar to the distribution of plasma irregularities at solar minimum. These signatures suggest that type I ULF oscillations are related to plasma irregularities that are common phenomena in the nightside F region ionosphere. The characteristics of type II ULF oscillations (without significant electron density perturbations) agree well with those features of mid-latitude ionospheric electric field fluctuations, which are not thought to be related to magnetospheric origins.