Cold Ion Heating by Magnetosonic Waves in a Density Cavity of the Plasmasphere

Author
Keywords
Abstract
Fast magnetosonic (MS) waves play an important role in the dynamics of the inner magnetosphere. Theoretical prediction and simulation have demonstrated that MS waves can heat cold ions. However, direct observational evidence of cold ion heating by MS waves has so far remained elusive. In this paper, we show a typical event of cold ion heating by magnetosonic waves in a density cavity of the plasmasphere with observations of the Van Allen Probe mission on 22 August 2013. During enhancements of the MS wave intensity in the density cavity, the fluxes of trapped H+ and He+ ions with energies of 10\textendash100 eV were observed to increase, implying that cold plasmaspheric ions were heated through high-order resonances with the MS waves. Based on simultaneous observations of ring current protons, we have calculated local linear growth rates, which demonstrate that magnetosonic waves can be locally generated in the density cavity. Our results provide a direct observational proof of the energy coupling process between the ring current and plasmasphere; that is, through exciting MS waves, the free energy stored in the ring current protons with ring distributions is released. In the density cavity of the plasmasphere, both cold H+ and He+ ions are heated by MS waves. As a result, the energy of the ring current can be transferred into the plasmasphere
Year of Publication
2018
Journal
Journal of Geophysical Research: Space Physics
Volume
9964297105115116391201191151792394251053495971179561204142121119214017912292115751072323122119431216011712144115
Date Published
02/2018
URL
http://onlinelibrary.wiley.com/doi/10.1002/2017JA024919/full
DOI
10.1002/2017JA024919