Cusp Aurora Appearing at the Dayside tip of Transpolar Arcs - Dependence on IMF and Dipole Tilt

Abstract: The aurora is a direct consequence of the Earth’s magnetic field interaction withthe solar wind and the interplanetary magnetic field (IMF). In this study, we examine thelocation of the cusp aurora when accompanied by transpolar arcs (TPAs) with the goal to finda dependence on the IMF. We compiled a dataset based on UV images of the Northern andSouthern Hemisphere taken by four satellites. The resulting dataset contains 79 cusp auroraevents, where 25 of the events are classified as multiple (three or more TPAs) TPA eventsand 54 as isolated (one to two TPAs) TPA events, during the time period of six monthsduring 2015/2016. The results of this study confirms the known correlation between the cuspaurora location and the dipole tilt. We show for the first time that this dependence is strongerduring isolated TPA events than for multiple TPA events. IMF Bx has also been shown toeffect the location of the cusp aurora, although the result is ambiguous. A much clearer resultwas presented for IMF Bz , confirming that a large majority of the cusp aurora events appearduring positive values for IMF Bz . Lastly, we confirm the well-known impact of IMF By on thecusp aurora location, while also presenting inconclusive results regarding the favoring ofhemispherical events for certain values of IMF By.