SuperDARN observations of the two component model of ionospheric convection

Abstract

We use a 20 year database of Super Dual Auroral Radar Network (SuperDARN) observations to investigate the two component model of ionospheric convection. A convection pattern is included in the database if it is derived from at least 250 radar vectors and has a distribution of electric potential consistent with Dungey-cycle twin vortex flow (a negative potential peak in the dusk cell and a positive potential peak in the dawn cell). We extract the locations of the foci of the convection cells from the SuperDARN convection patterns, and compare their dependencies on the north-south component of the interplanetary magnetic field, IMF Bz, and the auroral electrojet index, AL. We define a quantity, dMLT, as the hour angle between the dawn and dusk convection cell foci, which we use as a proxy for the extent to which the dayside or nightside component of the convection pattern is dominating. We find that at a fixed level of AL, dMLT decreases with increasingly negative IMF Bz, consistent with an increasing dominance of dayside reconnection. We also find that at a fixed level of IMF Bz, dMLT increases with increasingly negative AL, consistent with an increasing dominance of nightside reconnection, but only up to modest values of AL (to ˜-200 nT). As AL becomes further enhanced dMLT decreases again, which we attribute to an inherent dependence of AL on IMF Bz.