A confirmation of vertical acoustic resonance and field-aligned current generation just after the 2022 Hunga Tonga Hunga Ha’apai volcanic eruption

Abstract A strong volcanic eruption caused a clear vertical acoustic resonance between the sea surface and thermosphere. Its effects are observed as geomagnetic GPS-TEC oscillations near volcano its conjugate area. The at Apia Honolulu observatories with amplitude of about 2 nT 0.2 nT, respectively. started around 04:14 UT on January 15, 2022. appeared 04:21UT Apia, Samoa, only 7 min after start eruption. Because distance is 841 km, it takes 40 for sound wave to propagate from Apia. Therefore, more plausible assume that magnetic oscillation by waves propagated vertically upward ionosphere generated an electric current. coherent appearance located point strongly support idea ionospheric current over diverted field-aligned which flew opposite hemisphere Honolulu. earliest was 04:15UT eruption, 04:20 KOKV station in Hawaii. time-lag TEC variations Samoa Hawaii obtained cross-correlation analysis 4.5 or 8.5 min. These time differences much smaller than travel seismic islands. suggested field transmitted along variation Islands. sawtooth waveform analyzed possible generation mechanism discussed. Graphical