Polarization jet events and excitation of weak SAR arcs

Abstract

Polarization Jet (PJ), also known as Sub‐Auroral Ion Drift (SAID), events are supersonic westward plasma drifts on the equatorward edge of the diffuse aurora in the evening and nighttime sector. Their optical F‐region signatures are weak 630.0 nm red arcs colocated with regions of fast convection. These weak arcs resemble Stable Auroral Red (SAR) arcs observed during the recovery phase of magnetic storms, but have lower intensities, shorter lifetimes, and occur without a significant heat flux from the magnetosphere. Previous model studies underestimated the brightness of weak SAR arcs. We present calculations showing that ion‐neutral collisional heating and ion composition changes during PJ events may be an additional source of 630.0 nm emission, and propose experimental tests that could verify our modeling results.