A cyclone formation, eastward plume drag, ion-hydration process, and the consequent ionospheric changes following the 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption

In this paper, we investigate the possible mechanism behind the volcanic plume drag and the massive expansion of the ionospheric Total Electron Content (TEC) along the eastern longitudes by using near-field observations of the 15 January 2022 Hunga Tong-Hunga Ha'apai volcanic eruption. The meteorological omega parameter shows a dominant upward/downward movement of the air parcels along the eastern and southern sides of the volcanic eruption. This dominant air convection under the presence of the heavy moisture of volcanic plume and vector winds indicated the formation of a cyclone over and around the Tonga volcano. This cyclone dragged the heavy volcanic plume towards the eastern longitudes (150^oE – 180^oE). Moreover, we observe that the volcanic plume injected about 5 DU of Sulfur Dioxide (SO₂) and 30 kgm⁻² of the water content along the total atmospheric column. The chain reactions of Hunga Tonga volcanic trace gases with the gases present in the neutral atmosphere instigated an air ionization process, while under the presence of the heavy water content, these ions underwent an ion-hydration process that contributed to the electrodynamical changes in the region. These electrodynamical changes can be regarded as Atmospheric Chemical Potential (ACP) in the lower atmosphere. We observe a sharp increase in the ACP of ∼0.26 eV along the eastern longitudes (160–180°E) exactly above the dragged volcanic plume area. The long-term TEC changes that have been observed towards the eastern longitudes are the result of the ion-hydration process at the lower atmosphere. The statistical analysis showed a critical change during the day of the event up to ∼48 TECU with an increasing value of 28 and 18 TECU from the lowest and highest ranges before the event over the crater, respectively. Our main findings showed ionospheric anomalies in the near field started from 6:00 to 16:00 UTC. Based on Swarm satellites, the S4 values have significant changes around 0.3–0.6 lasting for tens of minutes.