Flux Transfer Events and Polar Patch Formation Observed by the RISR Radars

Abstract:

The two faces of the Resolute Bay Incoherent Scatter Radar (RISR) operate together for typically 5-10 days nearly every month. The north face (RISR-N) began operating in 2009 and the southward pointing Canadian face (RISR-C) began operating in 2015. The combined fields-of-view (FOV) of the two radars cover the F-region from ~68-82° in geographic latitude (~76-87° in geomagnetic latitude). During daytime, the FOV of the southward pointing RISR-C is within the area of the cusp and is also well suited for observing flux transfer events (FTEs) and subsequent polar patch formation. Of the nearly 300 days of joint RISR-C/RISR-N operations, over 100 have shown evidence FTEs. For many of these events (though not all), sunlit plasma flowing into the polar cap (i.e., the tongue-of-ionization (TOI)) is interrupted or segmented into patch-like structures by fast dawn-to-dusk (i.e., azimuthal) flows. The fast azimuthal flows and associated density depletions often show an enhanced ion temperature from Joule heating caused by the sudden change in plasma flow direction. These newly created polar patches are then observed as they propagate through the FOVs of both radars. Here we present preliminary results of a study examining these FTE/polar patch events and highlight the morphology of some of the most interesting occurrences, in particular, those that are associated with storms.