First Global‐Scale Synoptic Imaging of Solar Eclipse Effects in the Thermosphere. Issue 9 (18th September 2020)

• Record Type: Journal Article
• Authors: Aryal, Saurav; Evans, J. S.; Correira, John; Burns, Alan G.; Wang, Wenbin; Solomon, Stanley C.; Laskar, Fazlul I.; McClintock, William E.; Eastes, Richard W.; Dang, Tong; Lei, Jiuhou; Liu, Huixin; Jee, Geonhwa
• Is Part Of: Journal of geophysical research. Volume 125:Issue 9(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-18
• Subjects: Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA027789
• Languages: English
• ISSNs: 2169-9380

Abstract

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 N2 LBH band emissions compared to baseline measurements made 2 days prior. In addition, a significant enhancement (with respect to the baseline) in the ΣO/N2 column density ratio (~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 ΣO/N2 column density ratio (~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. Plain Language Summary: During total solar eclipses, solar radiation incident on parts of the Earth is blocked by the Moon. At Earth's surface, this creates almost night‐like conditions within totality. In the upper atmosphere, a reduction in solar radiation (>90% around totality) significantly decreases ionization, and the heating of the atmosphere is also reduced. These reductions also change the airglow emissions in the thermosphere. Since airglow emissions are produced by physical and photochemical processes in the upper atmosphere, changes in their brightnesses act as a proxy to these processes. In this paper, we present imaging observations of the eclipse's effects in the thermosphere. These effects are presented as brightness changes in prominent thermospheric ultraviolet emissions observed by NASA's GOLD mission from a geostationary orbit during the 2 July 2019 total solar eclipse. Key Points: First synoptic global‐scale observations of a solar eclipse's effect on the thermosphere are presented based on FUV imaging Greater than 80% reduction around eclipse totality is seen in OI 135.6 nm and N2 LBH emission brightnesses Enhanced ΣO/N2 column density ratio (~80%) is observed within eclipse's totality and after the eclipse (~7%) suggesting compositional changes