Effect of storm-time plasma pressure on the magnetic field in the inner magnetosphere

[1] We investigate the effect of plasma pressure on the magnetic field in the near-Earth magnetosphere (2 to 6.5 RE) during the major magnetic storm of October 21–25, 2001. For this we obtain a time series of ‘‘snapshots’’, in each of which the magnetic forces are equilibrated by plasma pressure gradient forces. Each snapshot is computed using our 3-D equilibrium code, which is fed anisotropic pressure in the equatorial plane from a kinetic ring current model. As computational boundaries we use magnetic flux surfaces obtained from the T89 empirical model [Tsyganenko, 1989], parameterized by the appropriate Kp. We analyze the computed magnetic fields and electric currents at each stage of the storm. Our findings include significant ( 10) plasma b and large field depressions near Earth at the storm peak. The results clearly show the necessity of a magnetically self-consistent treatment of plasma transport in storm modeling. Citation: Zaharia, S., M. F. Thomsen, J. Birn, M. H. Denton, V. K. Jordanova, and C. Z. Cheng (2005), Effect of storm-time plasma pressure on the magnetic field in the inner magnetosphere, Geophys. Res. Lett., 32, L03102, doi:10.1029/2004GL021491.