1986 Volume 38 Issue 11 Pages 1199-1221
The influence of the interplanetary magnetic field on solar wind-magnetosphere interactions is described. A finite-conductivity solution for the magnetic field B in the magnetosheath is constructed, and it holds even close to the magnetopause, where the frozen-flux approximation is invalid. The electric field E implied by the solar wind plasma bulk motion is determined, too. Magnetic field diffusion caused by finite conductivity results in only a partial screening of the outer field in a dissipative layer near the magnetopause, with residual Bn and Et penetrating into the magnetosphere. The dependence of the magnetic and electric fields at the magnetopause on the magnetic Reynolds number, Rm, is Bn-Rm-p and Et-Rm-p; Bt-Rmp, and En-Rmp where p=0.25. The Poynting vector flux over the magnetopause is independent of Rm and equal to -2.6×1011W for usual solar wind and IMF parameters. Assuming E11=0 on open magnetic field lines, it is possible to determine the electric field within the region of open magnetic field lines using IMF-dependent boundary conditions at the magnetopause. Field-aligned currents in this region (or in the polar cap) are derived from the equation Div (ΣE)=j11, where the ionospheric conductivity Σ is assumed uniform. Sunward convection for northward IMF is explained. A shift of the cusp projection in the ionosphere due to the IMF effect is presented. For northward IMF a two-vortex convection pattern in the polar cap is obtained. Comparison of model predictions with experimental data shows good agreement in the dayside polar cap. The proposed model provides a self-consistent analytic solution of the problem of IMF penetration into the magnetosphere.