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.