Fig. 13From: A confirmation of vertical acoustic resonance and field-aligned current generation just after the 2022 Hunga Tonga Hunga Ha’apai volcanic eruptionA simple model of vertical acoustic resonance. At a certain moment shown in this figure, we assume that all of the harmonic waves for upward or downward propagating waves have the same phase at the ground. The green arrows indicate the direction of phase variation at this moment for each harmonic waveBack to article page