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, even in the absence of electric currents, a polarization electric field appears along field lines to tie together ions and electrons. The present study focuses on this parallel electric field (ifE∥), the potential drop it implies across these magnetospheres, and its consequences on the mapping of the particle densities. We start from general expression of this field, in terms of centrifugal, gravitational and mirror forces. We conduct simple numerical simulations for n-component plasmae, where we analyze the influence of different parameters on the plasma equilibrium: the plasma anisotropy, the mass and temperatures of all species and the field line geometry. We apply the equilibrium model to existing plasma distributions at Saturn and Jupiter. Typical potential drops between the ionosphere and the equator are ∼ 30 Volts at Saturn and ∼ 300 Volts at Jupiter. Effects of E∥ on the mapping of particle densities along field lines of Saturnʹs and Jupiterʹs magnetospheres are discussed in detail.