  We consider the effects of a polarization electric field on transient ion
motion in a thin current sheet. Using adiabatic invariants, we analytically
describe a variety of ion trajectories in current sheet configurations which
include a local minimum or maximum of the scalar potential in the central
region. Ions in the current sheet can either be trapped or ejected more
efficiently than in an unpolarized current sheet, depending on the sign and
magnitude of the polarization electric field. We derive an expression for the
relative phase space volume filled by transient particles as a function of the
electric field amplitude. This expression allows us to estimate the dependence
of transient particle and current densities on the electric field. We discuss
applicability of these results for current sheets observed in planetary
magnetospheres.
