The Impact of Independently Derived Neutral Winds on Ionospheric Frictional Heating

Closure of field-aligned currents in the E-region ionosphere occurs through Hall and Pedersen currents which are set up because of ion-neutral collisions that allow ions to drift perpendicular to the mean magnetic field. Joule heating is a combination of the Pedersen conductivity and the electric field in the frame of the neutral winds and represents a sink of magnetospheric energy. The Pedersen conductivity, perpendicular electric field, and neutral winds have different dependencies on magnetic local time (MLT) and level of geomagnetic activity. The neutral wind profile is a particularly challenging aspect in the calculation of Joule heating. The most successful technique for producing altitude-resolved wind measurements is the chemical tracer technique, although other techniques using incoherent scatter radar have been developed. Previous ISR investigations have shown that the neutral wind can enhance or reduce energy deposition in both case studies and statistical investigations spanning MLT. These investigations use an in-directly calculation neutral wind profiles based on the deflection of the perpendicular ion drift. In this investigation, we use previous sounding rocket data comprised of four missions (Joule 1, Joule 2, Auroral Jets, and INCAA) launched from Poker Flat, Alaska, which forms a unique data set to investigate the neutral wind contribution to Joule heating. We use in situ measurements of the neutral wind profile (~1 km altitude resolution) and DC electric fields to investigate the contributions of fields, winds, and conductivities to Joule heating. In the absence of in-situ electron densities, we use Poker Flat Incoherent Scatter Radar (PFISR) observations with additional support from NRL-MSIS 2.1 and IRI-2020 to calculate the Pedersen conductivity. We present Joule heating rates with and without the thermospheric profiles as well as other related energy exchange parameters derived using the aforementioned datasets. We find the impact of the neutral wind varies depending on the geomagnetic conditions and impacts the amount of energy deposited by either enhancing or inhibiting frictional heating with the most significant variation found during the dusk sector. We find that without enhancements in geomagnetic activity (Kp ≤ 2), the inclusion of neutral wind increases the Joule heating rate by up to 25%. In contrast, with enhancements in geomagnetic activity (Kp ≥ 2) and the inclusion of the neutral wind, the Joule heating rate is reduced by up to 36%.