Responses of the AC/DC Global Electric Circuit to Volcanic Electrical Activity in the Hunga Tonga‐Hunga Ha'apai Eruption on 15 January 2022

• Published in: Journal of geophysical research. Atmospheres 2023-04, Vol.128 (8), p.n/a
• Main Authors: Bór, J., Bozóki, T., Sátori, G., Williams, E., Behnke, S. A., Rycroft, M. J., Buzás, A., Silva, H. G., Kubicki, M., Said, R., Vagasky, C., Steinbach, P., André, K. Szabóné, Atkinson, M.
• Format: Article
• Language: English
• Subjects: atmospheric electric potential gradient; atmospheric electricity; Charging; Circuits; Continents; Detection; Direct current; Earth surface; Electric field; Electric fields; Eruptions; Geophysics; GEOSCIENCES; global electric circuit; Hunga Tonga-Hunga Ha'apai volcanic eruption; Lightning; Lightning activity; Lightning detection; Lightning detection networks; Lightning discharges; Lightning strokes; Measurement; Polarity; Potential gradient; Schumann resonances; Time constant; Undersea; Volcanic activity; Volcanoes; Water pollution
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2022JD038238

Responses of the AC and DC global electric circuits (GECs) to the large eruption of the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcano on 15 January 2022 are discussed. The AC‐related investigation is based on Schumann resonance (SR) measurements from six stations on four continents. The DC‐related investigation utilizes atmospheric electric field (potential gradient, PG) measurements from six recording stations in Europe and the USA. According to data from the GLD360 and WWLLN lightning detection networks, the peak lightning stroke rate, 83/s, was dominated by negative polarity lightning, but the distributions of positive and negative lightning discharges in latitude and longitude around the volcano differed. A global intensification of SR is apparent in connection with the enhanced lightning activity caused by the eruption. SR data‐based results confirm that the lightning activity in the eruption dominated the naturally occurring global activity for a period of about 1 hr. The highly localized increase in lightning activity over HT‐HH was a unique point source of SR excitation. PG measurements suggest that impulse‐like charging of the DC GEC, by ∼15%, via negative cloud‐to‐ground lightning strokes took place twice during the eruption. A time constant of 7 or 8 min has been inferred for near‐surface PG changes due to these enhancements. This could be the first direct measurement of the time constant of the GEC near the Earth's surface, as well as the first observation of the direct charging of the DC GEC by a unique atmospheric electrified source. Plain Language Summary The eruption of the undersea volcano near Tonga on 15 January 2022 caused dramatic changes to both the AC and DC global electric circuits in association with the extremely intensive volcanic lightning activity, which was evaluated using data from global lightning detection networks. During the evolution over almost 2 hr of the lightning from the volcanic cloud, episodes of predominantly positive and negative polarity lightning alternated. As time progressed after the first explosion of the volcano at 4:16 UTC, lightning stroke locations formed rings of varying radius up to ∼150 km around the vent. A connection between the dynamics of the eruption and the varying lightning activity is plausible. For AC circuit investigations, Schumann resonances at six stations on four continents were found to be considerably stronger than usual during the lightning generated by the volcano. Measurements of the