Nonlinear disturbance of the dipole field by an axisymmetric plasma distribution

Abstract

The results of numerical modeling of magnetic field variations with increasing pressure in the inner magnetosphere regions in the axisymmetric case with pressure isotropy are presented. The radial dependence of magnetic field disturbance for the given plasma pressure distribution is determined. The dependence of magnetic field disturbance near the Earth on the total pressure with allowance for the influence of magnetic field of the currents in the plasma on the field value and distribution is obtained. The obtained solutions are applied in an analysis of the large magnetic storm of February, 1986, during which the minimum value of the Dst variation was 307 nT. The plasma pressure values experimentally measured near the equatorial plane were used. It is shown that, with allowance for nonlinear effects, the value of observed Dst variation corresponds to the disturbance caused by the axisymmetric part of a ring current.