THE KINETIC ALFVEN WAVE DRIVEN BY THE DENSITY INHOMOGENEITY AND THE MAGNETIC FIELD INHOMOGENEITY IN FINITE β PLASMA

Basing on the analysis on the drift wave instability caused by the density and magnetic field inhomogeneities in finite plasmas, we find that this instability has an effect on driving kinetic Alfven waves. The kinetic theory deals with the effect of finite Lamor radius and wave-particle interacting effectively and correctly. According to the motion of charged particles in the electromagnetic field, the Vlasov equation to describe the ion motion and the drift kinetic equation for electron motion were adopted. Comparing the effects on the drift instabilities between the density in homogeneity and the magnetic field inhomogeneity, it is found that the drift instability easily takes pace under the condition of the density inhomogeneity and the energy transfer much faster in this process. Driven kinetic Alfven waves occur after getting the energy from the instability. The numerical solutions indicate that the kinetic Alfven waves can be driven in magnetosphere widely, especially in the obviously inhomogeneous regions such as the cusp, magnetopause and the plasma sheet boundary layer. The results in this paper imply that the kinetic Alfven waves have great influence on the energy transfer in the magnetosphere.