Nonlinear Waves in Collisional Ionospheric Plasmas

摘要

A unified electrostatic MHD theory is developed to describe small-scale plasma structures with arbitrary amplitude moving in auroral ionosphere, or magnetosphere, with a constant velocity V in respect to ambient plasma, which is drifting under the action of large-scale electric field E. The theoretical model includes additional dissipative terms in comparison with that described in accompanying paper by the same authors. It accounts for ion and electron inertia, dynamic ion viscosity, deviation from quasi-neutrality. The equations are derived in respect to the variable S = x - Vt for one-dimensional models, and S = x + αz - Vt for a two-dimensional model. In the two-dimensional form of the theory for the strongly collisional case, the vector nonlinearity (or, Poisson brackets) gives the main stabilizing effect to the two-stream instability leading to a stationary turbulence level with density fluctuations of order 10% or more. Damped large-amplitude oscillations superimposed on an electrostatic shock are excited which can be VHF radar aurora scatterers for the non-zero aspect angles. Qualitative agreement with the results of radar aurora studies and in situ rocket measurements is found.