First Global­Scale Synoptic Imaging of Solar Eclipse Effects in the Thermosphere

Abstract

A total solar eclipse occurred in the Southern Hemisphere on 2 July 2019 from approximately 17 to 22 UT. Its effect in the thermosphere over South America was imaged from geostationary orbit by NASA's Global-scale Observation of Limb and Disk (GOLD) instrument. GOLD observed a large brightness reduction (>80% around totality) in OI 135.6 nm and N-2 LBH band emissions compared to baseline measurements made 2 days prior. In addition, a significant enhancement (with respect to the baseline) in the Sigma O/N-2 column density ratio (similar to 80%) was observed within the eclipse's totality. This enhancement suggests that the eclipse induced compositional changes in the thermosphere. After the eclipse passed, a slight enhancement in Sigma O/N-2 column density ratio (similar to 7%) was also seen around the totality path when compared to measurements before the eclipse. These observations are the first synoptic imaging measurements of an eclipse's thermospheric effects with the potential to drastically improve and test our understanding of how the thermosphere responds to rapid, localized changes in solar short wavelength radiation.