Earth's Auroral Acceleration Region: Comparison of Cluster data and Vlasov model results

Abstract:

Cluster observations at high magnetic latitudes have provided insight into the structure and location of Earth’s auroral acceleration region (AAR). In 2009, C4 passed through the AAR, followed by C1 and C3, which were near to magnetic conjugacy. This ideal configuration allowed for a determination of both the spatial and temporal characteristics of the field-aligned potential structure with altitude through the plasma and fields instrument [Forsyth et al. (2012)]. The observations indicated a quasi-static current structure during the C4 and C1/C3 passes, with a potential drop concentrated below 4685 km altitude. We apply a 1-D spatial, 2-D velocity space Vlasov model [Gunell et al. (2013,2015)] to the 2009 event. We impose the net potential drop determined by the Cluster spacecraft and compare the resulting spatial structure of the field-aligned potential and particle distributions to Cluster data. We discuss differences between the model and data and how they affect our understanding of quasi-static auroral acceleration.