Volcanic Disruption of the Equatorial Ionosphere: ICON Observations of the Tonga Eruption

The submarine Hunga Tonga-Hunga Ha'apai volcano (subsequently called 'Tonga') erupted on January 15, 2022 at approximately 4:15UT. Studies have shown that the eruption's effects quickly reached ionospheric heights, propelling traveling ionospheric disturbances (TIDs) and disrupting the ionospheric dynamo, with effects persisting hours or days after the eruption. The Ionospheric Connection Explorer (ICON) satellite passed near Tonga within an hour of the eruption, during which ICON's Ion Velocity Meter (IVM) was magnetically connected to the part of the E-region influenced by the eruption, taking measurements of plasma drifts and, by extension, electric fields generated during the eruption's immediate aftermath. During subsequent ICON orbits, the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) and Far Ultra Violet Imaging Spectrograph (FUV) instruments measured volcanic effects on the neutral winds and ion density profiles, respectively. In this work, we present ICON's observations of the Tonga eruption in the first several hours after the event, tracing the volcano's effect on the E-region dynamo via both E-region wind-driven dynamo electric fields and field-aligned drag. We present evidence that the eruption dramatically modified the ionosphere in a manner consistent with a large neutral wind perturbation blowing away from Tonga. This event, a sudden delta-function like energy input to the lower atmosphere, is a natural experiment for understanding how energy moves between parts of the atmosphere. These observations will also prove valuable for constraining and evaluating future modeling efforts of this event.