HR: 1340h
AN: SM13B-1322    [Abstracts]
TI: Ionospheric Response to the Changes in the Interplanetary Magnetic Field (IMF) B_z Under Strong Positive IMF B_y Conditions, as Seen using SuperDARN and PolarDARN Radars.
AU: Choudhary, R
EM:
AF: ISAS, University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N 5E2, Canada
AU: * St.-Maurice, J
EM: jp.stmaurice@usask.ca
AF: ISAS, University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N 5E2, Canada
AU: Sofko, G J
EM: george.sofko@usask.ca
AB: The interplanetary magnetic field (IMF) is known to have a profound influence on the ionospheric convection pattern at high latitudes. Thus, when the IMF has a dominant southward (B_z) component, the convection over the central polar cap is anti-sunward and closes through the dawn and dusk sectors to produce a familiar 2-cell convection pattern. For strong northward IMF conditions, the pattern is thought to break into four cells, with sunward convection taking place over the noon sector of the polar cap. For strong IMF B_y conditions the standard 2-cell convection pattern is believed to become asymmetric and/or to rotate from its basic alignment with the noon-to- midnight meridian to a more dusk-to-dawn or dawn-to-dusk alignment. With the help of the new PolarDARN radar in combination with other SuperDARN radar data, we have been able to observe changes occurring deep into the polar cap during a period of strong sustained positive IMF B_y, when the B_z component was always less than 20% of the B_y component in magnitude. The basic shape of the convection pattern was highly reminiscent of the Heppner-Maynard `BC' convection pattern predicted for strong positive B_y conditions ( Heppner and Maynard, JGR, 92, 4467, 1987). We note that we observed very clear changes in the convection pattern as B_z changed signs, with a distinct sub-cell on the evening side being present while the IMF B_z component was greater than zero. The sub-cell completely vanished when the B_z component changed sign. These variations were unexpected in view of the relatively small IMF B_z magnitudes involved. Interestingly enough, this feature would have been missed, had the PolarDARN radar data not been added to the data obtained with the rest of the SuperDARN radars. We will discuss the implications of our findings for our understanding of ionospheric/magnetospheric convection in response to solar wind inputs.
DE: 2463 Plasma convection (2760)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting