Steve and the Picket Fence: Evidence of Feedback-Unstable Magnetosphere-Ionosphere Interaction

This paper aims to extend the understanding of Strong Thermal Emission VelocityEnhancement (STEVE) and the Picket Fence related to strong subauroral ion drifts (SAID). Wenumerically demonstrated that precipitating energetic electrons are critical for the structuring of the PicketFence. It is created by feedback-unstable magnetosphere-ionosphere interactions driven by the SAIDelectric field when the Hall conductance created by energetic (≥1 keV) electrons exceeds the Pedersenconductance. We show that thermal excitation of the red-line emission in STEVE is inhibited by inelasticcollisions with molecular nitrogen. Suprathermal (≤500 eV) electrons coming from the turbulentplasmasphere appear to be the major source. We also show that the chemiluminescencent and radiativeattachment reactions do not explain the short-wavelength part of the STEVE continuum and argue thataccounting for vibrational excitation may resolve the problem. Atmosphere's upwelling due to enhancedion-neutral drag leads to the increased abundance of molecular components relative to atomic oxygen.