Effects of Storm-Time Winds on Ionospheric Pre-Midnight Equatorial Plasma Bubbles Over South America as Observed by ICON and GOLD

Abstract

This study uses satellite measurements of plasma densities and thermospheric winds to analyze the effects of the November 2021 geomagnetic storm on ionospheric pre-midnight topside plasma bubbles over South America. Using observations from the Ionospheric Connection Explorer (ICON) and the Global-scale Observations of the Limb and Disk (GOLD) satellites, we find that pre-midnight topside plasma bubbles were inhibited over eastern South America during the recovery phase of the storm. This is particularly notable because of the otherwise high occurrence rate of plasma bubbles at these longitudes during this season. This inhibition coincided with the recovery phase of the geomagnetic storm, marked by a northward turning of the z-component of the interplanetary magnetic field (IMFBz) and quiet-time values of the SuperMAG Auroral Electrojet Index (SME). We observed a westward turning of the zonal wind before the bubble inhibition, so we conclude the inhibition of topside plasma bubbles is likely related to a westward disturbance dynamo electric field (DDEF) causing a downward $E\times B$ drift and suppress the growth of the instability responsible for bubble development. Contrary to theoretical predictions, we do not observe notable changes to the meridional wind during the event. These results provide new insights into the ionosphere-thermosphere system's response to geomagnetic storms and highlight the role of wind patterns in inhibiting ionospheric irregularities, contributing to better predictive models for these phenomena.