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Earth, Planets and Space
Fig. 4 | Earth, Planets and Space

Fig. 4

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

Fig. 4Fig. 4

a High-pass filtered GPS-TEC data observed at Samoa (SAMO, left panel) and Kokee Park, Hawaii (KOKV, right panel). At both stations, fluctuations start at around 04:15–04:20 UT about 1–6 min after the start of volcanic eruption. The different color of the lines indicates different elevation angle of the satellites as indicated under the panels. b The TEC variations along the directions of satellites seen from the receiver of the GPS satellites for KOKV (right panel) and for SAMO (left). The sky above the elevation angle = 30° viewed from the ground is shown. The azimuth angle is measured westward from the south. ‘Snn’ with red font indicates the start point (04:00 UT) of the PRN = nn satellite and ‘Enn’ with blue font indicates the end point (05:00 UT). Note that the scale is different for KOKV and SAMO, i.e., the unit scale shown at the upper left corner is 0.2 TEC unit (TECU) for KOKV and 1.0 for SAMO. c The TEC observed at the MKEA station. The format of each panel is the same as that in a and b

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