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

Abstract

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.

New Method for Determining Azimuths of ELF Signals Associated With the Global Thunderstorm Activity and the Hunga Tonga Volcano Eruption

“…To illustrate the range of possibilities of the proposed ELF signal azimuth analysis applied to the ELA11 receiver measurements we selected the day of 15 January 2022 (0–24 hr UT). We processed the data to extract information on natural ELF wave fields anisotropies and additionally, to check constraints on revealing the ELF signature associated with the HT volcano eruption (Bor et al., 2023; Nickolaenko et al., 2022). The eruption signatures in the time range 4:15–15:50 UT for the main eruption and in the time range 8:35–9:30 UT for the next weaker one, are visible in our data, as presented in the 24‐hr dynamic spectrum evolution at Figure 2.…”

“…As described in more detail below, the novelty of the present approach is the use of a difference technique that intrinsically introduces selective temporal filtering that can be used to remove power line interference or target specific temporal signatures. Thus a significant amount of the measurement data can be applied for the azimuth determinations, contrary to previous studies focusing on large ELF impulses in the data (see, e.g., a recent description in Nickolaenko et al, 2023) For illustration of the possibilities of the proposed novel approach, we analyze observations from the day of 15 January 2022, when occurrence of the Hunga Tonga (HT) volcano eruption created a strong compact ELF source Mezentsev et al, 2022;Bor et al, 2023; see also Nickolaenko et al, 2023). We also present the capabilities of single site monitoring of global thunderstorm activity.…”

Recent Advances and Challenges in Schumann Resonance Observations and Research

“…Simultaneous observation of SR anomalies in France, Italy, Russia, and Japan were reported during the 2022 Tonga eruption, where localized lightning field sources were formed by aggregation in the eruption cloud [32]. J. Bor et al [33] used the data observed by multiple SR and PG (potential gradient) measurement stations distributed globally to study the GEC's response to the eruption of the Tonga volcano. SR and PG intensities were used to describe the AC (alternating current) and DC (direct current) components of the GEC, respectively.…”