[P-EM04_28PM1] New Perspectives on Earth's Inner Magnetosphere

[PEM04-10] Akebono observations of EMIC waves in the slot region of the radiation belts

*坂口 歌織¹、笠原 禎也²、小路 真史³、大村 善治⁴、三好 由純³、長妻 努¹、熊本 篤志⁵、松岡 彩子⁶ (1.情報通信研究機構、2.金沢大学総合メディア基盤センター、3.名古屋大学太陽地球環境研究所、4.京都大学生存圏研究所、5.東北大学大学院理学研究科地球物理学専攻、6.宇宙航空研究開発機構　宇宙科学研究所)

キーワード：EMIC wave, slot region of the radiation belt, mode conversion, triggered emission, ion compotision ratio, Akebono satellite

We present a unique observation of electromagnetic ion cyclotron (EMIC) waves in the deep inner magnetosphere at L = 2.5-5 made by the Akebono satellite at altitudes of 3,300-8,700 km. The mode conversion, i.e., L mode (He+ band)➞R mode (He+ band)➞L mode (O+ band) was clearly identified from the equator to high latitudes. In addition, we found rising tone structures, recently identified as EMIC triggered emissions, which could lead to bursty precipitation of relativistic electrons. First, we estimated the ion composition ratio (H+, He+, O+) = (83%, 16%, 1%) from polarization analysis. Second, we estimated minimum resonant electron energies with the observed EMIC waves and triggered emissions to be 1?10 MeV. The satellite trajectory during the wave observation was primarily through the slot region of electron radiation belts. The collocation implies possible contribution of EMIC waves to formation of the slot region of radiation belts after a magnetic storm.