HR: 1340h
AN: SM13B-1328    [Abstracts]
TI: Synthesis of Various Ionospheric Convection Patterns for IMF BY-Dominated Periods: Split Crescent Cells, Exchange Cells, and Theta Aurora Formation
AU: * Watanabe, M
EM: masakazu.watanabe@usask.ca
AF: University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N5E2, Canada
AU: Sofko, G J
EM: george.sofko@usask.ca
AF: University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N5E2, Canada
AB: When the dawn-to-dusk component of the interplanetary magnetic field (IMF B_Y) is dominant, ionospheric convection usually exhibits a distorted two-cell pattern with a round cell on the dawnside (or duskside) and a crescent-shaped cell on the duskside (dawnside). However, this convection pattern is an average picture, and actual convection sometimes deviates from the basic round/crescent cell pattern. Such nonstandard convection patterns include the dayside-enhanced crescent cell pattern, nightside-enhanced crescent cell pattern, split crescent cell pattern, and exchange cell pattern. Although at times the nonstandard convection patterns appear to be quite different from the basic round/crescent cell pattern, the underlying physical processes (i.e., reconnection) and field line topologies are basically the same. We show that, by considering the topologies of magnetic field lines involved in the eight types of reconnection that occur in IMF B_Y- dominated periods, these various convection patterns can be understood with one unified picture. We also discuss the formation mechanism of theta auroras in terms of magnetic topology and ionospheric convection. The theta aurora results from transient reconnection-driven convection when the IMF B_Y polarity switches. During the transition, the magnetospheric topology is expressed by a system with four magnetic nulls located on the separator circle encircling the Earth. The nightside portion of the separator circle (which corresponds to the plasma sheet in the magnetotail) is kinked at the two nulls on the nightside. The bifurcation of the polar cap occurs as a consequence of the accumulated closed magnetic flux around the kinked portion of the plasma sheet and the newly added open magnetic flux in the adjacent open field line region.
DE: 2411 Electric fields (2712)
DE: 2463 Plasma convection (2760)
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2760 Plasma convection (2463)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting