Modeling Sub-Alfvénic Outflow in Flare Reconnection via Interactions with the Surrounding Plasma Sheet

Abstract:

Observations of reconnection outflows of the September 10th 2017 X 8.2(SOL2017-09-10T15:35:00) flare place them at 300 km/s to 700 km/s. This is well below the Alfvén speed, which is the speed at which most reconnection models predict outflows. In this work, we attempt to reconcile model with observation by modeling retraction through the current sheet as a thin flux tube subject to a kind of aerodynamic drag force proportional to the square of the tube's velocity. This drag force is intended to represent the interaction with, and energy lost to, the plasma surrounding the current sheet. We use a simulation of a retracting flux tube to create a synthetic plasma sheet. In this sheet we find that slower retractions result in a plasma sheet with increased emission and lower temperatures. Conversely, we find that increasing the strength of the field outside the current raises the temperature lowers the emission. There appear to be value of both drag and magnetic field strength that are consistent with observation and result in both retraction speeds and plasma properties consistent with observation.