Intense Equatorial Electrojet and Counter Electrojet Caused by the 15 January 2022 Tonga Volcanic Eruption: Space‐ and Ground‐Based Observations

Abstract

We present space‐ and ground‐based multi‐instrument observations demonstrating the impact of the 2022 Tonga volcanic eruption on dayside equatorial electrodynamics. A strong counter electrojet (CEJ) was observed by Swarm and ground‐based magnetometers on 15 January after the Tonga eruption and during the recovery phase of a moderate geomagnetic storm. Swarm also observed an enhanced equatorial electrojet (EEJ) preceding the CEJ in the previous orbit. The observed EEJ and CEJ exhibited complex spatiotemporal variations. We combine them with the Ionospheric Connection Explorer neutral wind measurements to disentangle the potential mechanisms. Our analysis indicates that the geomagnetic storm had minimal impact; instead, a large‐scale atmospheric disturbance propagating eastward from the Tonga eruption site was the most likely driver for the observed intensification and directional reversal of the equatorial electrojet. The CEJ was associated with strong eastward zonal winds in the E‐region ionosphere, as a direct response to the lower atmosphere forcing.

Large‐Scale Disturbances in the Upper Thermosphere Induced by the 2022 Tonga Volcanic Eruption

“…The intense TIDs at ∼350 m/s speeds were found to be consistent with that of Lamb waves and propagated around the globe three times (S. R. Zhang et al., 2022). Due to the extreme change in the thermospheric winds and the associated equatorial electric field disturbance, equatorial ionization anomalies (EIAs) were found to be suppressed and reshaped after the eruption (Aa, Zhang, Wang, et al., 2022; Gasque et al., 2022; Harding et al., 2022; Le et al., 2022). Significant equatorial plasma bubbles (EPBs) and irregularity activities were observed (Aa, Zhang, Erickson, et al., 2022; Hong et al., 2022; Sun et al., 2022), and the ionospheric disturbances in the conjugate hemisphere were also suggested (Lin et al., 2022).…”

The Ionospheric Effects of the 2022 Hunga Tonga Volcano Eruption and the Associated Impacts on GPS Precise Point Positioning Across the Australian Region

“…This analysis begins with an overview of the ionospheric conditions before and after the arrival of the disturbances caused by the volcano eruption using the ionosonde network in Figure 1. First, it is worth mentioning that a moderate geomagnetic storm occurred in the late hours of 14 January, with Dst reaching −91 nT and Kp reaching 6‐ (Le et al., 2022). A useful way to analyze temporal changes in ionograms is by representing the data in a format similar to a “range‐time‐intensity” plot (Carter et al., 2018; Currie et al., 2021; Pradipta et al., 2015).…”

“…(2022) and Le et al. (2022) observed changes to the equatorial electrojet that were caused by variations in the ionospheric dynamo as a result of the eruption. Aa et al.…”

“…S.-R. Zhang et al (2022) showed evidence of these TIDs continuing to propagate around the world for at least 4 days. Harding et al (2022) and Le et al (2022) observed changes to the equatorial electrojet that were caused by variations in the ionospheric dynamo as a result of the eruption. Aa et al (2022) reported a localized ionospheric plasma depletion in the vicinity of the volcano and increased equatorial plasma bubble (EPB) activity in the Asia-Oceania low-latitude region, which has been further supported by recent modeling efforts (Huba et al, 2022).…”

A system science perspective of the drivers of equatorial plasma bubbles

“…Volcanic activity and other impulsive events can have a strong effect on space weather. The 2022 Hunga-Tonga eruption showed a strong effect on thermospheric winds and currents (Harding et al, 2022;Le et al, 2022), and left behind an ionospheric hole near the eruption and a trail of plasma bubbles after the shock wave passed (Aa et al, 2022).…”