Modulation of Dayside Reconnection During Northward IMF

Provan, G., Lester, M., Cowley, S.W., Grocott, A., Milan, S.E., Hubert, B., 
Khan, H.


On 17 September 2000 the IMF was directed continuously northward for more than
three hours. Density fluctuations in the solar wind resulted in quasi-periodic
variations in the solar wind dynamic pressure, and correlated fluctuations also
occurred in the IMF Bz component. The Northern hemisphere SuperDARN radars
observed bursts of high-latitude high-velocity plasma flow during this northward
IMF interval, both when ionospheric signatures consistent with low-latitude
merging were observed, and when lobe merging was occurring. On average the
recurrence period of these flow bursts was ~22 min. During this time the SI-12
spectrographic imager channel on the IMAGE spacecraft observed the dayside
proton auroral spot continuously (Frey et al., 2003). The brightness of the
auroral spot varied over time. Here we find a direct correlation between the
occurrence of bursts of plasma flow and periodic fluctuations in the brightness
of the proton auroral spot. Our results suggest that correlated fluctuations in
the solar wind dynamic pressure and IMF Bz component modulated ionospheric
precipitation and dayside reconnection, resulting in fluctuations in the
brightness of the proton auroral spot and periodic variations in the dayside
high-latitude plasma flow.

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Fall Meeting, American Geophysical Union, San Francisco, U.S.A., 
5-9 December 2005