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-EM12] Space Weather, Space Climate, and VarSITI

2018年5月24日(木) 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:片岡 龍峰(国立極地研究所)、Antti A Pulkkinen (NASA Goddard Space Flight Center)、草野 完也(名古屋大学宇宙地球環境研究所、共同)、塩川 和夫(名古屋大学宇宙地球環境研究所)

[PEM12-P23] GAIA simulations of the ionospheric response to successive X-class solar flares on September 6, 2017

*松村 充1塩川 和夫1大塚 雄一1品川 裕之2陣 英克2三好 勉信3藤原 均4垰 千尋2津川 卓也2新堀 淳樹1渡邉 恭子5西本 将平5今田 晋亮1川手 朋子6李 京宣7 (1.名古屋大学宇宙地球環境研究所、2.情報通信研究機構、3.九州大学、4.成蹊大学、5.防衛大学、6.宇宙科学研究所、7.国立天文台)

キーワード:電離圏、全電子数、太陽フレア

Solar flares enhance EUV and X-ray radiation to promote the ionization of the Earth's atmosphere, which increases the plasma density on the dayside ionosphere. Higher plasma density in the ionospheric F region degrades the Global Navigation Satellite System (GNSS), and in the E and D region can cause HF radio communication blackouts. The plasma density variation depends on the wavelength spectrum and temporal variation of the flare irradiance. They vary from flare to flare, and it is important to understand the various types of the ionospheric flare response. In this paper we focus on the two successive X-class flares that occurred on September 6, 2017: X2.2 peaking at 9:10 UT and X9.3 at 12:02 UT.

To understand how the ionosphere responded to the flares, we carried out numerical simulations using the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) [Jin et al., 2011]. We used the Flare Irradiance Spectral Model (FISM) [Chamberlin et al., 2007, 2008] to drive the GAIA. Model simulations showed that on the sunlit side, molecular ion density, which dominates the ionospheric E region, increased in several minutes and decayed in several hours in the same way as the two flare irradiances. The simulations also showed that atomic oxygen ion density, which dominates the ionospheric F region, increased with the first flare and sustained the enhancement until the second flare. Consequently, the density further increased with the second flare and the decay time was longer than that for single flare. When the molecular ion density was higher in the model, HF radio signals of ionosonde observations were under blackout. To further validate the model simulation, we will compare the simulated ion density with Total Electron Content (TEC) measured by ground GNSS receivers. We will also compare the simulated magnetic field variations with ones measured by ground magnetometers.

In addition, we will report another GAIA simulation with a physics-based flare irradiance model [Imada et al., 2011] instead of the FISM, an empirical model. We tuned the parameters of the physics-based irradiance model with statistical data of satellites so that the model can predict the irradiance spectra without measurement. We will compare preliminary results using the model with ones using the FISM.