The 2017 August 21 American total solar eclipse through the eyes of GPS

Abstract

We explored spatio-temporal variation in total electron contents (TEC) in the ionosphere caused by the recent 2017 August 21 total solar eclipse, which was observed over the United States of America. The path of the total solar eclipse passes through the continental parts of the United States of America, starting in the northwestern state of Oregon and ending in the southeastern state of South Carolina, approximately covering 4000 km length. Across this length, EarthScope Plate Boundary Observatory (PBO) has been operating a dense Global Navigation Satellite Systems (GNSS) networks. During the course of passage of the solar eclipse, the sudden decline in solar radiation by temporarily obscuration by the Moon caused a drop of ∼6–9 × 1016 electrons m2 in the ionosphere with time-delay at the cGPS sites. The significant drop in TEC at cGPS sites captured the average migration velocity of shadow along the eclipse path (0.74 km s−1), from which we estimated the Moon's orbital velocity (∼1 km s−1). Further, this event also caused some marginal increase in TEC during the eclipse in the Earth's ionosphere in the magnetically conjugate region at the tip of South America and Antarctica, consistent with the model predictions of SAMI3 by Naval Research Laboratory.