Impacts of the January 2022 Tonga volcanic eruption on the ionospheric
dynamo: ICON-MIGHTI and Swarm observations of extreme neutral winds and
The eruption of the Hunga Tonga-Hunga Ha’apai volcano on 15 January 2022
triggered atmospheric waves 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 Lamb 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 typically observed values.
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 strong westward winds in the Pedersen region
(~120-150 km). These observations imply that the dynamo
is a key mechanism in the ionospheric response to the Tonga disturbance.