Electromagnetic Ion Beam Instability in the Solar Corona

Abstract

The remote observations reveal that heavy ions in the corona undergo an anisotropic and mass-charge dependent energization. A popular explanation to this phenomenon is the damping of the Alfv´en/ion cyclotron waves. In this paper, we propose that the ion beam instability can be an important source of the Alfv´en/ion cyclotron waves, and we study the excitation of the ion beam instability in the corona at the heliocentric distance ∼3R⊙ and the corresponding energy transfer process therein based on plasma kinetic theory. The results indicate that the existence of the motionless heavy ions inhibits the ion beam instability. However, the anisotropic beams of heavy ions promote the excitation of the ion beam instability. Besides, the existence of α beams can provide a second energy source for exciting beam instability. However, when both the proton beam and the α beam reach the instability excitation threshold, the proton beam driven instability excites preferentially. Moreover, the excitation threshold of the Alfv´en/ion cyclotron instability driven by ion beam is of the local Alfv´en speed or even less in the corona.