M. O. Fillingim1, D. Chua2, G. A. Germany3, and J. F. Spann4
1Space Sciences Laboratory, University of California, Berkeley
2Space Science Division,
Naval Research Laboratory, Washington, DC
3Center for Space Plasma and Aeronomic Research,
University of Alabama in Huntsville
4NASA, Marshall Space Flight Center, Huntsville, AL
Presented at the 2009 Joint Assembly, Toronto, ON, Canada, 24 - 27 May 2009
Previous observations have shown that auroral activity and intense auroral emission are more common when the ionosphere is in darkness and are suppressed when the ionosphere is in daylight. This suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. More recent analyses have indicated that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) were roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). These results strongly suggest that auroral substorms in the northern and southern hemispheres develop differently during solstice conditions with substorms lasting longer in the dark (winter) hemisphere than in the sunlit (summer) hemisphere. This also implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. What is lacking, however, is a detailed investigation of how individual substorms develop in the conjugate hemispheres. Here, we extend earlier work by analyzing the recovery time scales for substorms observed in the conjugate hemsiphere simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. The results presented here will lead to new insights into the role of the ionosphere in the transport of energy during substorms.
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Matt Fillingim
matt at ssl dot berkeley dot edu
University of California, Berkeley
Space Sciences Laboratory # 7450
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