HR: 1340h
AN: SM13B-1219    [Abstracts]
TI: Day-side Aspects of Theta-aurora
AU: * Vennerstrom, S
EM: sv@dsri.dk
AF: Danish Space Research Institute, Juliane Maries Vej 30 , Copenhagen O, d100 Denmark
AU: Moretto, T
EM: tmoretto@lepvax.gsfc.nasa.gov
AF: NASA Goddard Space Flight Centre, NASA/GFSG Code696, Greenbelt, MD 20771 United States
AU: Rast\"atter, L
EM: lr@waipio.gsfc.nasa.gov
AF: NASA Goddard Space Flight Centre, NASA/GFSG Code696, Greenbelt, MD 20771 United States
AU: Raeder, J
EM: J.Raeder@unh.edu
AF: University of New Hampshire, 245G Morse Hall, 39 College Rd, Durham, NH 03824-3525 United States
AB: Global MHD-modeling has been used to study the magnetospheric effect of IMF changes typically observed in connection with the occurrence of theta-aurora. We find that the observed geometry of the polar cap, to a large extent, can be explained by the changing merging scenario at the dayside. During intervals of almost northward IMF the solar wind flux-tubes reconnect in both hemispheres, thereby converting open lobe field-lines to closed "double reconnected" day-side field-lines. Thus a predominantly northward IMF is associated with a closing up of the magnetosphere from the dayside. The closure occurs preferentially at either the dawn or the dusk-side depending on the sign of IMF By. Subsequent directional changes of the IMF invokes growth of a new polar cap at either the dusk- or the dawn-side depending on the sign of By and Bz.
DE: 2407 Auroral ionosphere (2704)
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2740 Magnetospheric configuration and dynamics
DE: 2776 Polar cap phenomena
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting