Effects of Heavy Ions on Kinetic Alfvén Waves

Abstract

Kinetic Alfvén Wave (KAW) is one of the low-frequency electromagneticfluctuations that are identified extensively in space plasmasby in situ observations of satellites and has been an interestingtopic for discussion widely in the fields of laboratory, space,and astrophysical plasmas because of its potential importancein plasma particle energization. Some satellite observationsshow that the number density ratio of the oxygen ionsto the ambient plasma is 30% ∼ 50%,sometimes, even as high as 80%. In this paper,effects of heavy ion species on KAWs are studied in a low-beta plasma.The results show that heavy ions not only considerablyreduce the propagation speed of KAWs, but also remarkablyinfluence the parallel component of perturbed electric field of KAWs(to the ambient magnetic field). The ratio of parallelto perpendicular components of perturbed field decreases(or increases) with the heavy ion abundance for KAWs dominated bythe electron inertial length (or by ion acoustic gyroradius).In particular, the resonant condition of KAWs with thermal electronsis modified by the heavy ion species.