The Magnetospheric Source of Theta Aurora Include Dayside and Nightside Multiple Reconnection Sites: SWMF Geospace Simulation Results

We present simulation results of a transpolar auroral arc event that show the arc formation occurs on both open and closed field lines and is sourced from both dayside and nightside magnetospheric reconnection. The dayside and nightside precipitation sources magnetically connect across the polar cap in a flow channel to create the transpolar arc structure. We simulate the 15 May 2005 transpolar arc event observed by the IMAGE satellite with the University of Michigan Space Weather Modeling Framework (SWMF) Geospace configuration. We compare the IMAGE observations to the simulation produced ionospheric Joule heating to identify the transpolar arc features captured by the model. The features exist within an anti-sunward flow structure and coincide with the location of the R1/R2 current reversal. We map the magnetic field lines from the arc features to the magnetosphere, revealing both dayside and nightside source regions. We use four-field junction analysis to determine that the source regions are within potential simulation reconnection sites. We simulate other transpolar auroral arcs to assess the generality of our results.