## A kinetic-MHD model for studying low frequency multiscale phenomena

Description:
A nonlinear kinetic-MHD model for studying low frequency multiscale phenomena has been developed by taking advantage of the single fluid MHD model`s simplicity and by properly accounting for core ion finite Larmor radius (FLR) effects and major kinetic effects of energetic particles. The kinetic-MHD model treats the low energy core plasma by a generalized MHD description and energetic particles kinetically; the coupling between the dynamics of these two components of plasmas is through the plasma pressure. The generalized MHD model for core plasma includes core ion FLR effects which provide a finite parallel electric field, a modified perpendicular velocity from the {bold E} {times} {bold B} drift, and a gyroviscosity tensor, which are neglected in the usual single fluid MHD description. The perturbed core plasma electron and ion densities, velocity and pressure tensor are determined from both the low frequency and high frequency gyro-kinetic equations. From the quasineutrality condition, we obtain the parallel electric field, which arises from the ion gryoradius effects. The kinetic-MHD model is closed by generalized pressure laws for the core and energetic plasmas. When ion gryoradius radius is on the order of the plasma equilibrium scale length, the Vlasov description may be adopted to describe the energetic particle dynamics. From the kinetic-MHD model we derive eigenmode equations for low frequency waves such as shear/kinetic Alfven waves (KAW) and ballooning-mirror modes. The kinetic-MHD model has been successfully applied to study ballooning-mirror instabilities to understand the field-aligned structure and instability threshold of compressional Pc 5 waves in the ring current region. It is also demonstrated that the ion FLR effects in the dispersion relation of KAWs are properly retained; note that these are not properly included in the popularly employed two-fluid equations because the gryoviscosity contribution is usually not retained. 18 refs., 2 figs.

Date:
May 1, 1996

Creator:
Cheng, C. Z. & Johnson, J. R.

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Partner:
UNT Libraries Government Documents Department