Oral Presentation

Perpendicular heating of cold ions and fast magnetosonic waves in the inner magnetosphere observed by Arase

Author(s): K. Asamura (JAXA), Y. Miyoshi (Nagoya U.), M. Shoji (Nagoya U.), R. Fujii (Nagoya U.), Y. Kasaba (Tohoku U.), Y. Kasahara (Kanazawa U.), A. Matsuoka (JAXA)

Presenter: Kazushi Asamura (JAXA)

Fast magnetosonic (MS) waves are commonly observed in the equatorial region of the inner magnetosphere. MS waves can play an important role for both accelerating and scattering the high-energy electrons. Also, past numerical simulations show MS waves can accelerate cold ions through cyclotron resonance, although the observational evidence is still unclear.
Arase (ERG) satellite found events of perpendicular heating of cold ions simultaneously with plasma wave activities of the MS waves. We found more than 200 events of the perpendicular heating of low-energy (10eV/q - a few keV/q) ions in a period between April 2017 to June 2018, and 70% of them coincide with the MS waves. These heated ions are distributed to all the MLT regions within magnetic latitude of +/-10deg, which is consistent with the region where the MS waves frequently observed. Except for the perpendicular heating by the MS waves, there are possible processes which can produce the enhancement of perpendicular ion flux, such as charge exchange and/or Coulomb collision losses at low altitude, and pitch angle dependence of ion drift around the Earth. We will present the observational results of the heated ions in perpendicular direction and the MS waves and possible mechanisms to produce them.