Impacts of the January 2022 Tonga volcanic eruption on the ionospheric dynamo: ICON-MIGHTI and Swarm observations of extreme neutral winds and currents
Brian J. Harding, Yen‐Jung Wu, Patrick Alken, Yosuke Yamazaki, Colin Triplett, T. J. Immel, L. Claire Gasque, S. B. Mende, Chao Xiong
Abstract
The eruption of the Hunga Tonga-Hunga Ha’apai volcano on 15 January 2022 disturbed the atmosphere at all altitudes. The NASA Ionospheric Connection Explorer (ICON) and ESA Swarm satellites were well placed to observe its impact on the ionospheric wind dynamo. After the lower atmospheric wave entered the dayside, Swarm A observed an eastward and then westward equatorial electrojet (EEJ) on two consecutive orbits, each with magnitudes exceeding the 99.9th percentile of typical variation. ICON simultaneously observed the neutral wind (90-300 km altitude) at approximately the same distance from Tonga. The observed neutral winds were also extreme (>99.9th percentile at some altitudes). The covariation of EEJ and winds is consistent with recent theoretical and observational results, indicating that the westward electrojet is driven by a strong westward Pedersen-region wind. This result confirms that the eruption not only created small-scale waves in the thermosphere-ionosphere but also caused unprecedented large-scale electrodynamic modifications.