A Multi-Parametric and Multi-Layer Study to Investigate the Largest 2022 Hunga Tonga–Hunga Ha’apai Eruptions

Abstract

On 20 December 2021, after six quiet years, the Hunga Tonga–Hunga Ha’apai volcano erupted abruptly. Then, on 15 January 2022, the largest eruption produced a plume well registered from satellites and destroyed the volcanic cone previously formed in 2015, connecting the two islands. We applied a multi-parametric and multi-layer study to investigate all the possible pre-eruption signals and effects of this volcanic activity in the lithosphere, atmosphere, and ionosphere. We focused our attention on: (a) seismological features considering the eruption in terms of an earthquake with equivalent energy released in the lithosphere; (b) atmospheric parameters, such as skin and air temperature, outgoing longwave radiation (OLR), cloud cover, relative humidity from climatological datasets; (c) varying magnetic field and electron density observed by ground magnetometers and satellites, even if the event was in the recovery phase of an intense geomagnetic storm. We found different precursors of this unique event in the lithosphere, as well as the effects due to the propagation of acoustic gravity and pressure waves and magnetic and electromagnetic coupling in the form of signals detected by ground stations and satellite data. All these parameters and their detailed investigation confirm the lithosphere–atmosphere–ionosphere coupling (LAIC) models introduced for natural hazards such as volcano eruptions and earthquakes.

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.…”

“…Using magnetic data from a few INTERMAGNET observatories, scalar eld and electron density data from the Swarm and CSES satellites, 9 performed a multi-parametric investigation of the Hunga-Tonga volcanic outburst. In addition to the scalar residual of the magnetic eld measured by the Swarm constellation correlating with the oscillation caused by the volcanic eruption, the API observatory also detects oscillations in the magnetic eld near the main eruption that is not seen at the other observatories, further con rming the observed feature is purely of local origin.…”

“…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.…”

“…Although few research works were already carried out to understand the morphology of this event during the day/night time ionosphere using multi-instrument observations by satellites, Global Navigation Satellite System, Ionosonde, and VHF radar measurements 3,13,14 , the more features on the geomagnetic eld disturbances 1,10,11,15 , the response of the SR signals due to the lightning strikes and the propagation velocity of the gravity wave 9,10 remain to be analyzed, since the observations are restricted to only a few longitudes.…”