HR: 09:43h
AN: SM11C-07 INVITED    [Abstracts]
TI: Comparison of dayside and nightside reconnection changes resulting from a sudden enhancement in solar wind dynamic pressure
AU: * Boudouridis, A
EM: thanasis@atmos.ucla.edu
AF: UCLA, Department of Atmospheric and Oceanic Sciences, 405 Hilgard Avenue, 7127 Math Sciences, Los Angeles, CA 90095-1565, United States
AU: Zesta, E
EM: ezesta@atmos.ucla.edu
AF: UCLA, Department of Atmospheric and Oceanic Sciences, 405 Hilgard Avenue, 7127 Math Sciences, Los Angeles, CA 90095-1565, United States
AU: Lyons, L R
EM: larry@atmos.ucla.edu
AF: UCLA, Department of Atmospheric and Oceanic Sciences, 405 Hilgard Avenue, 7127 Math Sciences, Los Angeles, CA 90095-1565, United States
AU: Ruohoniemi, J M
EM: Mike.Ruohoniemi@jhuapl.edu
AF: APL/JHU, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AU: Lummerzheim, D
EM: lumm@gi.alaska.edu
AF: University of Alaska, Geophysical Institute, Fairbanks, AK 99775-7320, United States
AU: Anderson, P C
EM: phillip.anderson1@utdallas.edu
AF: University of Texas at Dallas, Center for Space Sciences, 2601 North Floyd Road, PO Box 830688, Richardson, TX 75083-0688, United States
AB: Magnetic reconnection at the dayside magnetopause is the main process by which mass, energy, and momentum from the solar wind enter the terrestrial magnetosphere. Magnetic reconnection at the nightside energizes magnetotail plasma and closes the lobe open flux, thus completing the cycle that initiates and sustains magnetospheric convection. Understanding the drivers of reconnection and convection in the magnetosphere is one of the primary goals of magnetospheric physics. It has long been recognized that the Interplanetary Magnetic Field (IMF) is the most influential factor in initiation of reconnection and convection in the magnetosphere. Recent evidence has shown that the solar wind dynamic pressure plays also an important role in enhancing both dayside and nightside reconnection, and driving enhanced ionospheric convection. Super Dual Auroral Radar Network (SuperDARN) observations show that solar wind pressure fronts induce significantly enhanced ionospheric convection in the dayside ionosphere. In parallel, Defense Meteorological Satellite Program (DMSP) precipitating particle measurements and POLAR Ultra-Violet Imager (UVI) images have demonstrated that sudden solar wind pressure increases also significantly affect the size of the polar cap. The polar cap is observed to shrink after an increase in solar wind pressure, especially on the nightside, suggesting an enhancement of magnetotail reconnection. MHD models of the interaction of the magnetosphere with solar wind pressure fronts have managed to reproduce the enhancement of dayside reconnection, but have failed so far to account for the observed closing of the polar cap on the nightside and the suggested magnetotail reconnection increase. We use SuperDARN observations of ionospheric convection within both the dayside and nightside polar ionosphere, including near the magnetic separatrix, to evaluate the relative strengths of the observed dayside and nightside reconnection enhancements after an abrupt increase in solar wind dynamic pressure. We show that enhancements of both dayside and nightside convection occur after an increase in pressure, suggesting an increased reconnection rate on both sides of the ionosphere. We discuss these results in terms of a competition between dayside and nightside reconnection in the determination of the size of the polar cap and possibly their effect on the transpolar potential.
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2744 Magnetotail
DE: 2760 Plasma convection (2463)
DE: 2776 Polar cap phenomena
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting