有限β等离子体中密度和磁场不均匀驱动的动理学Alfven波

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

在分析有限β等离子体中的密度、磁场不均匀引起的漂移波不稳定性的基础上,剖析了漂移波不稳定性对动理学Alfven波激发的作用.动理学理论能正确地处理有限拉莫半径效应和波粒共振相互作用,本文根据带电粒子在电磁场中的运动特性,采用Vlasov方程描述离子运动,运用漂移动理学方程对电子运动进行描述.密度不均匀和磁场不均匀对产生漂移不稳定性的对比分析表明:在有限β等离子体中,密度不均匀比磁场不均匀更易激发漂移不稳定性,且密度不均匀激发漂移不稳定性中的能量转换和转移更为强烈.这种能量的转换为动理学Alfven波的激发提供了物理基础.所得数值解表明:动理学Alfven波在磁层中能广泛地被激发产生,特别是在磁层空间的极尖区、磁层顶和等离子体片边界层等具有明显的不均匀性区域中更容易被激发产生.本文的研究结果进一步表明动理学Alfven波对磁层空间中能量传输具有重要作用.

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.