Dartmouth Events

Abstract: We present a series of simulations designed to investigate the "picket fence" phenomena associated with STEVE (Strong Thermal Emission Velocity Enhancement) events in the sub-auroral ionosphere. The picket fence is an optical emission that usually presents itself as a series of green filaments in the E region of the ionosphere alongside the usual thin purple signature of STEVE events. In this paper, we build upon previous work suggesting an ionospheric driver for the picket fence phenomena by means of tearing-mode unstable currents (such as the currents that drive filamentary arcs in the auroral zone). This is in contrast to previous papers which suggest that the picket fence is a signature of precipitation from the magnetosphere. In these simulations, we investigate how the morphology of the SAID (Sub-Auroral Ion Drift) events that drive STEVE and the background density of the ionosphere affect the formation of strong currents. We find that current density is significantly enhanced by counterstreaming flows and increased background densities. This finding provides further guidance for determining drivers of the picket fence. 

********************************************************************************************************

Join Zoom Meeting
https://dartmouth.zoom.us/j/98372494556?pwd=a3VSRWZFcFB6VGZCTVlTVGZiNFFNdz09

Meeting ID: 983 7249 4556
Passcode: McManus