MHD modelling of magnetosphere tail reconnection in sawtooth event

E. V. Gubanov¹ - A. P. Likhachev¹ - S. A. Medin^{1, 2}

¹ RAN Joint Institute for High Temperatures, 13 Izhorskaya str., bld. 2, Moscow 125412, Russia
² Moscow Institute of Physics and Technology, 9 Institutskii per., Dolgoprudny 141700, Russia

Abstract
The magnetosphere response to the solar wind forcing at various values of the plasma resistivity is studied. The simulation is performed within a two-dimensional MHD resistive model; the meridional plane is considered. The solar wind and southward interplanetary magnetic field are supposed to be stationary. The calculations were made for two plasma resistivity values η = {10⁶; 10⁴} Ωm given by constants in the whole flow field. The plasma resistivity was specified on the basis of the spacecraft measurements of the bow shock width. At higher plasma resistivity steady magnetospheric convection takes place; at lower resistivity the sawtooth event is realized. The sequence of sawtooth cycle phases is analyzed in terms of the open magnetic flux and reconnection rates. The evolution of the magnetic force lines and velocity vector lines in every phase is described. In the (x,t) diagram, the movement of axial positions of boundaries between dipole, interplanetary and island magnetic fields is plotted. In the growth and expansion phases, a vortex train is generated in the tail dipole sector. The reconnection at the magnetosphere dayside occurs through two x-points positioned symmetrically at the top and bottom peaks of the magnetic island. Figs 7, Refs 16.