The case for a rocket campaign targeting subauroral dynamics

Recent optical observations in the subauroral region highlight the need for better measurements in an area of the ionosphere colloquially termed the “ignorosphere.” Examples include STEVE’s unusual multi-wavelength emissions (e.g., Gillies et al., 2019; Mende et al., 2020) which have been theorized to be excited in situ and not by precipitation (e.g., Harding et al., 2020; Gallardo-Lacourt et al., 2018; Nishimura et al., 2019). Fundamental questions pertaining to STEVE cannot be closed without in situ measurements of the composition of the neutral and ionized gasses. In addition, direct reports on the temporal and spatial evolution (order of minutes) from bright SAR arcs into STEVE (e.g., Martinis et al., 2022) highlight the rapid and extreme dynamic that takes place in the subauroral region. Both of these phenomena have been linked to subauroral ion drifts (SAID).

While several quasi-stationary theories have attempted to explain the formation of such fast subauroral flows (e.g., Anderson et al., 1993; Mishin et al., 2003), they cannot explain the temporal evolution reported in recent years. Moreover, the available numerical simulations cannot account for the extreme conditions reported by the new studies. To fully understand the rapid and small-scale dynamics of the subauroral ionosphere, new in-situ subauroral measurements are required not only in the zonal and meridional components, but also in altitude.

Ground-based measurements and satellite data (e.g., SuperDARN, Swarm, DMSP) currently do not provide the measurements required to fully study the sub-auroral ionosphere. Although Incoherent Scatter Radars could provide the needed vertical profiles in a limited area, most of these instruments are located either poleward or equatorward from the area of interest. However, sounding rockets possess the capability to directly measure the altitudinal profiles of the subauroral region. Sounding rocket campaigns, therefore, present a potential opportunity to help us understand the observed temporal and spatial evolution of phenomena associated with intense subauroral ion drifts.