Nonsteady state ionosphere‐plasmasphere coupling of superthermal electrons

Abstract

Numerical solutions to the nonsteady state kinetic equation which describes the transport of superthermal electrons in the ionosphere and plasmasphere between the magnetically conjugate regions of the ionosphere are presented. The distribution function in time, distance along arbitrary geomagnetic field lines, energy, and pitch angle are among the parameters calculated by the model. This model represents a unified approach by self‐consistently coupling the interaction of the two hemispheres and the trapping of superthermal electrons in the plasmasphere. Our calculations take into account the various ionization and excitation processes and the effect of an inhomogeneous magnetic field (i.e., magnetic mirroring of precipitating electrons and focusing of escaping electrons along magnetic field lines). Omnidirectional flux spectra and pitch angle distributions are shown for various L shells and situations, and the features are described in detail. Nonsteady state calculations predict that a depleted flux tube can take several hours to reach steady state levels again. Plasmaspheric transparencies are calculated for different conditions of illumination, scattering processes in the conjugate ionospheres, and field‐aligned gradients of the thermal plasma density. Plasmaspheric transparency is found to be a complicated function of not only the plasmaspheric thermal plasma but also the ionospheric sources and scattering processes. A phenomenological model is used to describe the energy transmission, reflection, and deposition in the plasmasphere. By studying the ionosphere and plasmasphere as one system rather than two separate ones, substantial corrections are introduced in the values of key parameters describing photoelectron fluxes.