1Space Sciences Laboratory, University of California, Berkeley
2E. O. Hulbert Center for Space Research,
Naval Research Laboratory, Washington, DC
3Center for Space Plasma and Aeronomic Research,
University of Alabama in Huntsville
4NASA, Marshall Space Flight Center, Huntsville, AL
The hypothesis that ionospheric conductivity plays a major role in the global-scale dynamics of the aurora is further evaluated in this study. The substorm recovery time scale during auroral intensifications are computed for over three hundred substorms observed by the Polar Ultraviolet Imager (UVI) and the IMAGE Far Ultraviolet Imager (FUV) in both hemispheres and then sorted according to season. The substorm recovery times are well ordered by whether or not the nightside auroral region is sunlit: substorms occurring in the winter and equinox periods have similar recovery time scales which are both roughly a factor of two longer than that for summer when the auroral oval is sunlit. These results strongly suggest that simultaneous auroral intensifications in the northern and southern hemispheres develop differently during solstice conditions. We expect the auroral breakup in the dark (winter) hemisphere to be more intense and longer lived than that observed 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 a substorm. Simultaneous, conjugate auroral substorm observations by Polar UVI and the IMAGE FUV instrument are used to confirm this behavior. The observed hemispheric asymmetry and non-conjugacy of auroral substorms is consistent with the suppression of discrete aurora in sunlight and highlights the importance of this effect in magnetosphere-ionosphere coupling.
PDF presentation (1.5 MB)
Return to Matt's Publications and Presentations page
Return to Matt's Home Page