Asymmetric Ionospheric Fluctuations Over the Circum‐Pacific Regions Following the January 2022 Tonga Volcanic Eruption

Abstract

The Hunga Tonga‐Hunga Ha'apai volcanic eruption on 15 January 2022 had a significant impact on the ionosphere‐thermosphere system, resulting in large‐scale ionospheric irregularities with longitudinal and latitudinal asymmetries. Multiple instruments recorded these irregularities, indicating the propagation of a westward wave at an average velocity of 354 ± 8 m/s, which led to plasma irregularities of 0.2 TECu/min. Conversely, an eastward‐propagating wave was detected on the Pacific's east coast, traveling at a speed of 348 ± 6 m/s, with a corresponding decrease in plasma fluctuations to 0.1 TECu/min. In Asia, noticeable plasma irregularities appeared within a few hours after the eruption, and the maximum speed exceeded 1,100 m/s, which cannot be explained by the acoustic wave model. There was also a significant latitudinal asymmetry of ionospheric disturbances in the Asian‐Oceania sector, with the plasma density around Oceania depleted by 2–3 orders of magnitude within the altitudes of ∼150–575 km, while the ion density over Asia was enhanced by 1–2 orders of magnitude, and was uplifted ∼50 km. The plasma temperature was proportional to ion density, indicating the ion temperature reduced ∼500 K and increased 100–200 K around Oceania and Asia, respectively. The equatorial electric field, vertical E × B drifts and thermospheric O/N2 density ratio also fluctuated significantly following the eruption, indicating the redistribution of charged particles due to the magnetic field mapping effect, which was the main contributor to the asymmetries observed.

3D Traveling Ionospheric Disturbances During the 2022 Hunga Tonga–Hunga Ha’apai Eruption Using GNSS TEC

“…The HTHH volcanic eruption occurred during the recovery phase of a moderate geomagnetic storm. Previous studies (Aa et al, 2022;Astafyeva et al, 2022;Li et al, 2023) stated that this geomagnetic storm had minimal impact on TEC. It was found that the peak of the average TIDs was at ∼09:00-10:00 UT or ∼300 min after eruption with ∼24.8 TECU.…”

“…During the event, disturbance on the electric field is responsible for generating the westward equatorial electrojet (EEJ) (Zhang et al, 2021(Zhang et al, , 2022b. Previous research (Aa et al, 2022;Astafyeva et al, 2022;Li et al, 2023) stated that geomagnetic storms might affect TEC, although its effect might be insignificant. In addition, Le et al (2022) stated that the eruption and the geomagnetic storm reversed the neutral wind direction.…”

The impact of the Hunga Tonga–Hunga Ha’apai volcanic eruption on the Peruvian atmosphere: from the sea surface to the ionosphere

“…Atmospheric pressure disturbances traveled in the form of Lamb waves and surrounded the Earth several times. The volcano eruption can produce effects in the lower atmosphere (varying atmospheric pressure), in the mesosphere and lower thermosphere (MLT) region (modifying neutral winds), as well as in the ionosphere (perturbing the horizontal magnetic field component-H, the vertical plasma drifts, the equatorial electrojet-EEJ, and the virtual height of the ionograms) (Poblet et al 2023;Stober et al 2023;Schnepf et al 2022;Le et al 2022;Sun et al 2022;Li et al 2023;Harding et al 2022;Qiu et al 2023).…”