HYBRID SIMULATION OF THE CURVED DAYSIDE MAGNETOPAUSE DURING SOUTHWARDIMF

Large-scale, 2-D hybrid (fluid electrons, particle ions) simulations h ave been performed to investigate the macroscopic and the microscopic structure of the dayside (curved) magnetopause during southward IMF. I t is found that in addition to the formation of an X-line at the subso lar point, other X lines are formed at higher latitudes. The locations of these X lines are asymmetric with respect to the magnetic equator, and the resulting plasmoids have different sizes. The thickness of th e magnetopause varies considerably as a function of latitude. In addit ion, the spatial scales associated with the plasma variations across t he magnetopause are considerably different than those associated with the field variations. The rotational (current) layer exhibits a linear polarization and does not match the jump conditions of any known disc ontinuity. Instead, the topology of the magnetic field lines, determin es the spatial scale and the polarization of the current layer.