[P-EM16] Dynamics of Earth's Inner Magnetosphere and Initial Results from Arase

[PEM16-04] Electron Scattering by Chorus Waves Generating Pulsating Aurora

★Invited Papers

*笠原 慧¹、三好 由純²、横田 勝一郎³、三谷 烈史⁴、笠原 禎也⁵、松田 昇也²、熊本 篤志⁶、松岡 彩子⁴、風間 洋一⁷、Frey Harald⁸、Angelopoulos Vassilis⁹、栗田 怜²、桂華 邦裕¹、関 華奈子¹、篠原 育⁴ (1.東京大学、2.名古屋大学、3.大阪大学、4.宇宙科学研究所、5.金沢大学、6.東北大学、7.ASIAA、8.UCB、9.UCLA)

キーワード：ピッチ角散乱、コーラス波動、ERG（あらせ）

Pulsating aurorae, which are quasiperiodic, blinking patches of light tens to hundreds of kilometres across, appear at altitudes of about 100 kilometres in the high-latitude regions of both hemispheres, and multiple patches often cover the entire sky. This auroral pulsation, with periods of several to tens of seconds, is generated by the intermittent precipitation of energetic electrons (several to tens of kiloelectronvolts) arriving from the magnetosphere and colliding with the atoms and molecules of the upper atmosphere. A possible cause of this precipitation is the interaction between magnetospheric electrons and electromagnetic waves called whistler-mode chorus waves. However, no direct observational evidence of this interaction has been obtained so far. Here we report that energetic electrons are scattered by chorus waves, resulting in their precipitation. Our observations were made in March 2017 with a magnetospheric spacecraft equipped with a high-angular-resolution electron sensor and electromagnetic field instruments. The measured quasiperiodic precipitating electron flux was sufficiently intense to generate a pulsating aurora, which was indeed simultaneously observed by a ground auroral imager.