The Dynamic Reconnection-Driven Polar Cap as seen by HF Radar (PolarDARN)

The SuperDARN HF radar pair (called PolarDARN) at Rankin Inlet (73.2° AACGM LAT) and Inuvik (71.2° AACGM LAT) is now fully operational (Rankin, May 2006 and Inuvik, Nov. 2007). For the first time, detailed two-dimensional radar convection maps of the polar cap region and poleward portion of the auroral oval are available with a one-minute time resolution. These radar images show clearly the signature of reconnection in the proximity of the ionospheric mapping of the OCFLB (open-closed field line boundary). Near magnetic noon (midnight), high-speed flows into (out of) the polar cap, away from (toward) the radars, are seen regularly, presumably mapping the fast outflows from the dayside and nightside reconnection regions. The convection maps reveal a very dynamic polar cap, with substantial changes in the convection pattern from one minute to the next. Examples of the reconnection-driven convection are presented, for By-dominant conditions and for both Bz+ and Bz- IMF conditions. The noon region for Bz+ conditions appears to be the counterpart of the auroral proton spot seen clearly with the IMAGE FUV instrument (Frey et al., JGR, 107, A7, 2002; Fusilier et al., JGR, 107, A7, 2002; Frey et al., Nature, 426, 533, 2003; Phan et al., GRL, 30, 10, 2003).