A quasi‐static magnetospheric convection model in two dimensions

Abstract

A self‐consistent, two‐dimensional model of subsonic, plasma sheet convection is presented. Specifically, time sequences of static equilibrium solutions for the two‐dimensional magnetospheric magnetic field are constructed consistent with adiabatic convection. This model self‐consistently includes a dipole field and a reasonable accounting for the effects of inner magnetospheric shielding. Starting from a relaxed magnetospheric equilibrium, the earthward convection of plasma sheet flux tubes results in the stretching of inner plasma sheet field lines, the development of a local minimum in the equatorial magnetic field Be in the near‐Earth plasma sheet, and an increasing lobe magnetic field. This evolution in time occurs generally, independent of the specific magnetopause or far‐tail boundary conditions, provided the plasma sheet is not at marginal interchange stability. This behavior results solely from the convection of flux tubes of increasing entropy into the near‐Earth plasma sheet. We discuss these results in the general context of earthward convection in Earth's plasma sheet and in the specific context of magnetospheric substorms.