EFFECTS OF SPATIAL DIFFUSION IN THE INNER PLASMA SHEET AND THE STRUCTURE OF THE DIFFUSION TENSOR

A standard pair equations is used to describe the behaviour of a singl e monoenergetic particle (proton or electron) population on a geomagne tic flux tube drifting in the magnetosphere. When particle losses from the drifting flux tube into the ionosphere are neglected, this behavi our is adiabatic in a thermodynamic sense. For a population of particl es with an isotropic pitch-angle distribution, the generalization of t hat system of equations is obtained by adding radial and azimuthal spa tial diffusion terms. The magnetic field is taken to be dipolar in the inner magnetosphere. The potential electric field is assumed to consi st of magnetospheric convection and corotation components. Experimenta l data are used to estimate the radial equatorial profiles of the plas ma sheet pressure. Assuming that the local time and L-shell variations are separable and supposing steady-state conditions, the expressions for the diffusion tensor components are evaluated. The influence of sp atial diffusion on the radial and azimuthal profiles of the plasma pre ssure in the inner plasma sheet is also discussed.