A document by L. Claire Gasque. Click on the document to view its contents.

A document by L. Claire Gasque. Click on the document to view its contents.

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.

The 15 Jan 2022 Hunga Tonga-Hunga Ha’apai volcano eruption drove global atmospheric waves that propagated into space and impacted the ionosphere. Here we show immediate large-scale electrodynamic effects of the eruption using observations from NASA’s Ionospheric Connection Explorer. We report extreme zonal and vertical ExB ion drifts thousands of kilometers away from Tonga within an hour of the eruption, before the arrival of any atmospheric wave. The measured drifts were magnetically connected to the ionospheric E-region just 400 km from Tonga, suggesting that the expanding wavefront created strong electric potentials which were transmitted along Earth’s magnetic field. A simple theoretical model suggests that the observed drifts are consistent with an expanding wave with a large (>200 m/s) neutral wind amplitude. These observations are the first direct detection in space of the immediate electrodynamic effects of a volcanic eruption and will help constrain future models of impulsive lower atmospheric events.