GPS Virtual Array Beamforming of Ionospheric Total Electron Content Disturbances Associated with Solar Eclipses

On August 21, 2017 a total solar eclipse crossed the United States from the Pacific to Atlantic coasts. For the first time during this event, an ionospheric total electron content (TEC) bow wave produced by the shadow of the moon, theorized in the early 1970s, was recorded by thousands of GNSS stations in North America. Several authors analyzed the bow wave using keograms, TEC versus time plots that provide qualitative results by observing lineaments in the TEC time series. We report on the application of Virtual Array Beamforming to quantify the wave propagation properties of the bow wave and other TEC disturbances associated with the eclipse. The advantage of beamforming is that it provides quantitative results on the propagation azimuth and velocity as a function of frequency of the TEC disturbances. We also present preliminary results of TEC perturbations observed during the recent July 2, 2019 eclipse in South America. During this eclipse, the elevation of the sun was low which gave us the opportunity to observe the effect of obscuration at very low, near tangential, elevation angles.