Simulation study on the nonlinear evolution of EMIC instability

  • Rha, Kicheol (Department of Physics, Pohang University of Science and Technology) ;
  • Ryu, Chang-Mo (Department of Physics, Pohang University of Science and Technology) ;
  • Yoon, Peter H. (IPST, University of Maryland)
  • Published : 2012.10.17

Abstract

Charged particle energization is an outstanding problem in space physics. This paper investigates the nonlinear dynamics of Alfve'n-cyclotron waves accompanying particle heating processes and the drift Alfv'en-cyclotron (or EMIC) instability associated with a current disruption event on 29 January 2008 observed with THEMIS satellite by means of a particle-in-cell simulation. The simulation shows that the drift Alfv'en-cyclotron instabilities are excited in two regimes, a relatively low frequency mode propagating in a quasi-perpendicular direction while the second high-frequency branch propagating in a predominantly parallel propagation direction, which is consistent with observation as well as earlier theories. It is shown that parametric decay processes lead to an inverse cascade of Alfv'en-cyclotron waves and the generation of ion-acoustic waves by decay instability. It is also shown that the nonlinear decay processes are accompanied by small perpendicular heating and parallel cooling of the protons, and a pronounced parallel heating of the electrons.

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