The Role of Neutral Winds in MIT Energy Transfer

The E-region ionosphere is the region where field-aligned currents terminate because of enhanced ion-neutral collisions enabling perpendicular closure currents. The closure of these currents enables energy to be dissipated through Joule heating. Thayer, 1998; Aikio et al., 2012; Cai et al., 2013; and Zahn et al., 2021; have shown that the neutral wind can play a significant role in enhancing or reducing energy dissipation. The observations presented were primarily derived from incoherent scatter radar observations that self-consistently calculated the neutral wind. Sangalli et al., 2009 presented one of the only case studies to quantify the impacts of the neutral winds on Joule heating using rocket-based observations. Since 2009, several other campaigns have derived neutral winds using the chemical tracer technique, and combined with observations from the Poker Flat Incoherent Scatter Radar (PFISR), there is a unique opportunity to quantify the impact of the neutral winds on the Joule heating over a range of magnetic local time sectors and geomagnetic activity levels. Direct TMA observations provide high-resolution (~1 km) neutral wind data that is notably independent of other measurement techniques.

In this investigation, we present results that combine PFISR data with in-situ data taken during five separate sounding rocket campaigns: HEX-2, JOULE II, MIST, JETS, and INCAA. For each campaign, altitude-resolved neutral wind profiles have been determined via TMA observations which are triangulated using the line-of-sight projection method between 80-130 km. Where applicable, the impact of in-situ measured electric fields are compared with the impact PFISR-derived results have on energy exchange parameters. The Joule heating rate, including the effects of the neutral winds, are quantified during these experiments and the associated geomagnetic conditions. Our results assess the impact independently derived neutral winds have on Joule heating in the E-region spanning over multiple magnetic local time sectors and geomagnetic activity levels.