THE MAGNETIC-FIELD-ALIGNED POLARIZATION ELECTRIC-FIELD AND ITS EFFECTS ON PARTICLE DISTRIBUTION IN THE MAGNETOSPHERES OF JUPITER AND SATURN

In the magnetospheres of Saturn and Jupiter, it is well known that, ev en in the absence of electric currents, a polarization electric field appears along field lines to tie together ions and electrons. The pres ent study focuses on this parallel electric field (E-parallel to), the potential drop it implies across these magnetospheres, and its conseq uences on the mapping of the particle densities. We start from a gener al expression of this field, in terms of centrifugal, gravitational an d mirror forces. We conduct simple numerical simulations for n-compone nt plasmae, where we analyze the influence of different parameters on the plasma equilibrium: the plasma anisotropy, the mass and temperatur es of all species and the field line geometry. We apply the equilibriu m model to existing plasma distributions at Saturn and Jupiter. Typica l potential drops between the ionosphere and the equator are similar t o 30 Volts at Saturn and similar to 300 Volts at Jupiter. Effects of E -parallel to on the mapping of particle densities along field lines of Saturn's and Jupiter's magnetospheres are discussed in detail. (C) 19 97 Published by Elsevier Science Ltd. All rights reserved.