Current Closure and Joule Heating in Data‐Driven 3‐D Auroral Arc Simulations

Discrete auroral arc systems, despite many symmetries, are three‐dimensional in nature, encapsulating latitude and longitude variations in precipitation and field‐aligned currents combined with important altitude variations in conductivities, hence closure currents. This study presents data‐driven, 3‐D numerical simulations of these processes based on a coordinated campaign of heterogeneous measurements collected from the Poker Flat Research Range during a sequence of Swarm spacecraft overpasses. These measurements include field‐aligned current, global‐scale convection flow, and auroral emissions, which are used to create top‐boundary drivers for auroral arc simulations. Six conjunctions between the spacecraft, all‐sky imagers, and radars are investigated and their measurements are used to simulate auroral arcs through multiple iterations per conjunction event. We look at different estimates of the background convection flow, assumptions about the energy distributions of electron precipitation, and along‐arc structures in field‐aligned current, and see what effect they have on current closure and Joule heating in auroral arc systems. Across the six conjunction events, 11 comparisons of auroral arc systems are presented, covering a catalog of 17 simulations in total. These comparisons allow us to look at the sensitivity of auroral arc systems to input parameters and envelop the simulations in a qualitative confidence interval. Our results suggest that discrete aurorae should be studied in three dimensions to fully understand field‐aligned current closure and, by extension, Magnetosphere‐Ionosphere‐Thermosphere coupling. Additionally, our results demonstrate that both large‐scale convection flows and specifics about the energy distributions of auroral precipitation can significantly affect current closure and Joule heating in auroral arc systems.