EFFECT OF ANISOTROPIC THERMAL-CONDUCTIVITY ON THE TEMPERATURE STRUCTURE OF THE IONOSPHERE-PLASMASPHERE SYSTEM

Anisotropic plasma hydrodynamics makes use of two heat fluxes represen ting the transfer of field-aligned and transverse (with respect to the external magnetic field) energies to describe thermal energy transfer . This is a considerably more complex treatment than isotropic plasma hydrodynamics in which only one heat flux component is considered. The present work analyzes the heal flux structure within the framework of anisotropic hydrodynamics and examines the effect of the anisotropic heat fluxes on the thermal plasma distribution both in the ionosphere and in the magnetically connected plasmasphere. The dependence of heat conductivities on the anisotropy parameter a=T-perpendicular to/T-par allel to is studied (T-perpendicular to and T-parallel to are transver se and field-aligned temperatures, respectively). The heat conductivit ies increase with field-aligned temperature (with decreasing value of a), thereby enhancing the thermal energy transfer. The analytical solu tion obtained for the heat conduction equation is used to examine the effect of the electron energy distribution anisotropy on the electron temperature in the plasmasphere. The dependence of heat conductivity o n the parameter a has been shown to result in a variation of electron temperature compared with the isotropic case (a=1). The calculated pla smaspheric temperature values rise when a > 1 and fall when a < 1. The strongest effect of the temperature anisotropy on the derived value o f the electron temperature occurs at high altitudes along a flux tube in the vicinity of the equatorial plane. Predictions of this simplifie d analytical model are compared to observations of temperature anisotr opies in the ionosphere. Basic agreement in the magnitude and sense of the electron temperature anisotropy between the model and observation s is found.