Short-Term Evolution of the Prereversal Enhancement as Observed by ICON

The evening prereversal enhancement (PRE) of zonal electric fields, and associated vertical plasma drifts, in the equatorial F-region has been seen to vary significantly from day to day. This variation is suspected to be due to changes in neutral winds and/or conductivities, but this has not been significantly quantified. Due to the strong connection between the PRE and equatorial spread F (ESF), understanding the evolution of the PRE is crucial for being able to predict ESF events. Comparing short-term PRE evolution to that of neutral winds may prove valuable as well. The ICON satellite provides an opportunity to sample the PRE approximately every 97 minutes (ICON's orbital period) and observe the structure's short-term evolution. Measured vertical drifts are compared between sequential orbits where the satellite passes through similar local times and magnetic dip angles. A persistence measure is developed to quantify how quickly the PRE changes, both in strength and timing relative to the day-night terminator. Similar methods are applied to neutral wind observations, and evolutionary patterns are compared between plasma drifts and neutral winds. The results are discussed in the context of developing a persistence-type forecast for the PRE based on observations at a Westward longitude. If successful, such a forecast may be suitable for driving a forecast for ESF.