A two-dimensional, time-dependent, near-earth magnetotail

Abstract

The plasma particle distributions in the near-earth region of the earth's magnetosphere (6–12 R e ) appear to have a complicated structure both in velocity space and real space. Recent observations and theoretical work have emphasized the role of non-isotropic particle distributions in this region. A kinetic approach may be necessary to describe field/plasma configurations in the near-earth magnetotail. We present such an approach for obtaining slowly time-dependent, self-consistent plasma and magnetic field configurations for this region, using anisotropic particle distributions. At present, a two-dimensional configuration is used. The time variation of the plasma/field configuration is assumed to be driven by a slowly varying, externally imposed electric field (representing, for example, a change in solar wind conditions). The numerical approach involves solving a two-dimensional non-linear Poisson equation for the magnetic vector potential at each time step. The local current density is calculated from particle velocity distributions under the assumption of adiabatic particle motion. The obtained equations of state will be compared with those of double-adiabatic theory. Numerical examples of self-consistent responses of the near-earth plasma and field to an externally imposed electric field pulse will be presented.