Atmospheric resonant oscillations by the 2022 January 15 eruption of the Hunga Tonga-Hunga Ha'apai volcano from GNSS-TEC observations

Continuous Plinian eruptions often excite atmospheric modes of similar to 3.7 and similar to 4.4 mHz, which are observed as harmonic oscillations of ionospheric total electron content (TEC) by global navigation satellite system (GNSS) receivers. Such TEC oscillations started shortly after the great eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) submarine volcano at similar to 4:14 UT, on 2022 January 15. Here I analyse GNSS data at stations within similar to 4000 km from the volcano to study temporal and spatial distribution of such atmospheric modes. Strong similar to 3.7 mHz TEC oscillations in near fields started shortly after the eruption onset and propagated outward with the sound speed from HTHH. Later such TEC oscillations became strong again with the amplitude peak at the distance similar to 1400 km from HTHH. Such far field oscillations occurred also above New Zealand and the Solomon Islands, similar to 3000 km from HTHH. Their amplitudes seem correlated with those of the 0S29 solid earth mode, suggesting that vertical surface vibrations underneath may play a role in maintaining the atmospheric mode. Onset of the far field TEC oscillations are synchronized with the local sunrise, possibly controlled by diurnal changes in the ionospheric electron density.