[P-EM11] Dynamics of the Inner Magnetospheric System

[PEM11-11] Cross-energy coupling between magnetosonic waves to electromagnetic ion cyclotron waves through cold ion heating

*Kazushi Asamura¹, Masafumi Shoji², Yoshizumi Miyoshi², Yoshiya Kasahara³, Yasumasa Kasaba⁴, Atsushi Kumamoto⁴, Fuminori Tsuchiya⁴, Shoya Matsuda³, Ayako Matsuoka⁵, Mariko Teramoto⁶, Yoichi Kazama⁷, Iku Shinohara¹ (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.ISEE, Nagoya University, 3.Graduate school of natural science and technology, Kanazawa university , 4.Graduate school of science, Tohoku University , 5.Graduate school of science, Kyoto University , 6.Graduate school of engineering, Kyushu Institute of Technology, 7.Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan)

Keywords:Magnetosonic waves, Electromagnetic ion cyclotron waves, Ion heating, Wave - particle interaction analysis

Fast magnetosonic waves (MSWs) are commonly observed in the equatorial inner magnetosphere. Past numerical simulations show that MSWs can accelerate low-energy ions through cyclotron resonance, although the observational evidence is still unclear. The Arase satellite found an event of perpendicular heating of low-energy protons simultaneously with enhancement of MSWs. Using the wave-particle interaction analysis (WPIA), we obtain direct evidence of energy transfer from the observed MSWs to the low-energy (26 – 725 eV) protons. We found these protons give their energies to electro-magnetic ion cyclotron (EMIC) waves with frequencies just below the local proton cyclotron frequency. Since MSW is excited by a ring-like distribution of ions, this analysis suggests that a part of energies of the ring current ions is transferred to the low-energy ions through excitation and damping of MSWs in the inner magnetosphere, and then, a part of the transferred energies is spent to excite high-frequency EMIC waves.