Auroral proper motion and the dynamics of auroral shear boundaries

Quiet, discrete auroral arcs are linked to key open questions in magnetosphere-ionosphere-thermosphere (MIT) coupling. A debated issue is whether arc motion reflects energy transfer in the system. While views differ, arcs consistently appear in regions of strong plasma convection shear. We suggest that arcs are a signature of non-ideal MIT coupling, where field-aligned electric fields (E_∥ ≠ 0) and particle acceleration enable faster energy dissipation than ideal coupling (E_∥ = 0) allows. If arcs are confined to regions of maximum convection shear, then their proper motion is inherently tied to the dynamics of the shear boundaries themselves. We present a preliminary analysis of arc proper motion using observations from various all-sky imagers and radar measurements from the Fast Borealis Ionosphere data product from SuperDARN.