Characterization of Ionosphere-Thermosphere Coupling from the VISIONS-2 Mission

Abstract:

VISIONS-2 was a NASA sounding rocket mission consisting of two payloads flown on December 7^th, 2018 from Svalbard, Norway. One of the payloads carried two electrostatic analyzers (mini-plasma imagers) that observed low energy ionospheric ions by collecting 2-dimensional images of ion arrival angles and energies. The present study aims to characterize the transition from collisionless to collision-dominated ionospheric-thermosphere interaction near 120 km altitude by determining the 3-dimensional ion drift along the VISIONS-2 trajectory. Using an instrument simulator to model the ion imagery, the ion drift and its uncertainty are estimated at regular altitude intervals throughout the transition region. Assuming a constant electric field and zero thermospheric wind, the variation of ion drift with altitude is studied to determine the altitude at which friction balances the Lorentz force on the ions. Results are interpreted within the context of existing in situ studies of the mechanics of ionosphere-thermosphere coupling within the E region.