HR: 0800h
AN: SM31B-1237    [Abstracts]
TI: Geosynchronous particle flux disturbances caused by the solar wind dynamic pressure enhancement: Dependepnce on convection strength
AU: * Lee, D
EM: dae-young-lee@hanmail.net
AF: Chungbuk National Univ, Dept of Astronomy and Space Science, Cheongju, 361-763 Korea, Republic of
AU: Lyons, L
EM: larry@atmos.ucla.edu
AF: UCLA, Dept of Atmospheric Sciences, Los Angeles, 90095-1565 United States
AB: When a variation in the solar wind dynamic pressure hits the magnetosphere, various types of disturbances are created. The geosynchronous particle flux disturbance is closely related to the issues of magnetic storms, substorms, and sawtooth oscillations. In this work, using the LANL particle flux data, we have done an intensive examination on how the geosynchronous particle flux in the energy range of tens to hundreds of keV responds to a sudden increase in the solar wind dynamic pressure. We find significant differences in the flux response between different conditions of the accompanied IMF (interplanetary magnetic field). When the IMF remains northward at and prior to the time of the pressure increase, the most common type of the flux response we find is a simple dispersionless increase simultaneously at all availbale MLT positions. However we also find a significant number of events where the flux response is a decrease or virtually no notable change at all. Also, for this northward IMF condition, we find no notable differences in the flux response between protons and electrons. When the accompanied IMF is weakly southward, the flux response to the pressure increase is very similar to that in the case of the northward IMF. However, as the IMF becomes further southward, the flux response becomes more complex. When the IMF remains strongly southward (around -10 nT or even less) at and prior to the pressure increase, we find that the flux change is strikingly different between different species. In a number of events we have examined, the electron flux response is characterized by dispersionless increases near midnight and by well-defined dispersions at MLT regions away from midnight. This feature is very similar to the flux change pattern during a typical substorm injection. In contrast, the proton flux often exhibits global near-simultaneous increases with little or even no energy dispersion at (dayside) MLT locations where one would normally expect a significant dispersion signature from a typical substorm injection. We will discuss how our result is associated with magnetic storms, substorms, and sawtooth phenomena.
DE: 2720 Energetic particles, trapped
DE: 2730 Magnetosphere--inner
DE: 2778 Ring current
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting