Virtual array beamforming of GPS TEC observations of coseismic ionospheric disturbances near the Geomagnetic South Pole triggered by teleseismic megathrusts

We identified coseismic ionospheric disturbances (CID) in Antarctica generated by the 2010 Maule and the 2011 Tohoku‐Oki earthquakes analyzing total electron content (TEC) data with a modified beamforming technique. Beamforming in Antarctica, however, is not straightforward due to the effects of array deformation and atmospheric neutral wave‐ionospheric plasma coupling. We take these effects into account and present a method to invert for the seismically generated acoustic wave using TEC observations. The back azimuths, speeds, and waveforms obtained by the beamform are in excellent agreement with the hypothesis that the TEC signals are generated by the passage of Rayleigh waves from the Maule and Tohoku‐Oki earthquakes. The Tohoku‐Oki earthquake is ~12,500 km from Antarctica, making this the farthest observation of CIDs to date using GPS. Key Points The geomagnetic poles enhance the generation and detection of teleseismic CIDs Beamformed apparent velocity and azimuth of CIDs produced by the Maule and Tohoku‐Oki earthquakes Development of virtual array beamforming of acoustic wave signals inverted from TEC data