Connection between bow shock and cusp energetic ions

Abstract

[1] A linkage between energetic ions in the bow shock and the cusp is established using a three-dimensional (3-D) self-consistent global hybrid simulation, for a case of the interplanetary magnetic field (IMF) condition favoring high-latitude magnetic reconnection and inter-connection between field lines in the quasi-parallel bow shock and the cusp. A diffuse ion distribution is obtained in the quasi-parallel shock and foreshock region, where large-amplitude waves and turbulence are present. Its energy spectrum is well described by an exponential function as in the case for upstream diffuse ions previously observed. These bow shock accelerated ions, upon being transmitted into the cusp region, form the bulk of cusp energetic ions. By tracing particles from the solar wind to the cusp, it is found that the source of acceleration for the cusp energetic ions is predominantly in the quasi-parallel shock and foreshock region, through a Fermi-type acceleration mechanism. Contribution to the cusp energetic ions from magnetosheath/cusp waves and magnetic reconnection appears relatively minor. Owing to the limitation of the model used, the magnetospheric source for energetic particles in the cusp cannot be fully investigated.