Global Electromagnetic Disturbances Caused by the Eruption of the Tonga Volcano on 15 January 2022

Abstract

The study is devoted to the analysis of geomagnetic field disturbances and the response of the Schumann resonance (SR) during the eruption of the Tonga volcano in 2022. The data on geomagnetic field variations at distances from 800 to 15,000 km from the volcano according to the INTERMAGNET network and parameters of SR signals recorded at Mikhnevo Observatory in Russia were used. The source of global geomagnetic disturbances are acoustic–gravity waves (AGWs), which caused changes in ionospheric conductivity, values of ionospheric currents, and the geomagnetic field. The propagation velocity of magnetic disturbances 263 ± 5 m/s, corresponding to the AGWs velocity, was determined and an independent estimate of the time of the eruption phase that caused the generation of the atmospheric wave (4:14 ± 10 UT) was obtained. A new method of processing the results of measurements of SR disturbance with a time resolution of 5 min instead of the usual 10–15 min allowed not only to detect but also to study this phenomenon in detail. The peculiarities of signals related to the number and energy of lightning discharges were revealed. Synchronous measurements of SR signals and geomagnetic field variations in a single observatory for the first time allowed to obtain an independent estimate of the eruption time and the electromagnetic disturbance propagation rate.

Evidence of Lightning and Gravity wave signatures produced by the Hunga-Tonga Volcanic eruption on Global geomagnetic data

“…3, it is obvious that there is a strong correlation between the lightning discharge from the volcano during the period 04:15 − 05:45 UT hours and the three SR modes detected at LEMI-30 at the Patiyasar observatory. Our results are strongly corroborated by the increase in the frequency range (7-21Hz) of the rst three SR modes as observed at four Finnish observatories and one Russian observatory, which is in coherence with the effects of global lightning activities during the eruption time 9,12 .…”

“…From 4:15 UT onwards, the signal power has steadily increased across in all frequencies. The resulting spectra are consistent with the rst three SR modes (SR1, SR2, and SR3), where the disturbances were seen to have the greatest amplitudes in the scalar and horizontal eld components at Finnish and Russian observatories as observed 9,12 . Further, we have computed the diurnal uctuations of SR modes and compared them with the available GLD360 network data between 04.17 and 06.13 UT 18 , to assess the impact of the lightning discharges related to the volcanic eruption on the Himalayan area.…”

“…Figure 5b also provides an equation: y = 0.001025x + 4.0 which determines the time of the atmospheric disturbance on the day of the volcanic eruption with a time error of 10-15 min 19 . Therefore, the obtained wave propagation velocity in this study is determined to be 271 ± 5 m/s, which is close to the velocity of the AGWs 12,20,21 . A thorough analysis of the scalar data revealed geomagnetic uctuations caused by the propagation of atmospheric-ionospheric waves created by the eruption at various distances from the source.…”

“…Following 12 , the gravity wave propagation velocity for all the observatories is identi ed from the reconstructed scalar component of the geomagnetic eld by the time of registration of negative bay with respect to the distance from Tonga. The registration time of negative bay for the MIK observatory is directly taken from the above-published literature.…”

“…Search Coil Magnetometer data from the Finnish pulsation magnetometer network (Sodankyla, Nurmijarvi, Oulu and Kevo), 9 showed the high total power at 7-9 Hz and at the upper harmonics (about 14 Hz), frequencies characteristic of the Schumann resonance associated with the effects of global lightning activities between 04:15 and 05:45 UTC, in a wider range of frequency (i.e., a higher power from 6 to 18 Hz) and concluded that the features detected in the spectrograms could be the effects of the volcanic thunderstorm associated with the friction of particles recorded in the cloud of ash and gas produced by the eruption. 12 Recently presented observations on geomagnetic eld disturbances and the response of the SR signals recorded at Mikhnevo Observatory (Russia) during the eruption, as well as the propagation velocity of magnetic disturbances is 263 ± 5 m/s by using 10 INTERMAGNET Observatories located at distances ranging from 800 to 15,000 km from the volcano. This study also proposed a new method of processing the results of SR disturbance measurements with a time resolution of 5 minutes rather than the usual 10-15 minutes, allowing not only to detect but also to study the SR phenomenon in great detail about the peculiarities of signals related to the number and energy of lightning discharges.…”