Magnetospheric Convection During an Extended Interval with Southward Interplanetary Magnetic Field

Recently we reported on a new convection state of the magnetosphere in which the late growth phase and expansion phase of a large magnetospheric substorm on December 22, 1996 were characterized by large twin vortical flows in the near-Earth magnetotail [Ashour-Abdalla et al. 2003]. We also found a state in which flux tubes formed by reconnection at a near-Earth neutral line do not convect to the dayside magnetopause. Instead these flux tubes convect around one of the vortices back to the tail neutral line where they reconnect with IMF field lines formed by the original neutral line and return the flux to the tail lobes. A second interval on February 13 and 14, 2001 was very similar to December 22, 1996 in that the interplanetary magnetic field remained southward for many hours. In this talk we will present the results from a study of convection during this event. February 13 and 14, 2001 were characterized by a number of substorms. The largest of which started at about 2200 on February 13 with significant intensifications at about 0030UT and 0500UT on February 14. We have used a global magnetohydrodynamic simulation to model the interval starting at 2000UT and including this substorm. A persistent near-Earth neutral line formed during this interval between x=-30RE and x=-50RE. A large-scale vortex formed earthward of the neutral line in the pre-midnight quadrant. This vortex intensified during the event eventually encompassing the entire magnetosphere earthward of the neutral line with earthward flows in the dawn quadrant and tailward flows in the dusk quadrant. The earthward flow reverses direction in the high-pressure region of the inner tail. Flux tubes in this large vortex reconnect with IMF field lines to form new closed field lines.