Thermospheric response to the June 11, 1983, solar eclipse

Abstract

The NCAR thermospheric general circulation model (TGCM) that includes coupling of dynamics and composition is used to calculate the time‐dependent thermospheric response to the June 11, 1983 total solar eclipse. The path of totality originated at sunrise in the Indian Ocean near 35°S and 60°E. The path moved equatorward passing through Indonesia near 5°S latitude 125°E longitude and ending near 20°S latitude and 165°E longitude in the vicinity of the Solomon Islands. Although the path of totality is relatively small, the area of partial shadow is relatively large, and the total flux incident on the dayside earth decreases by about 7% during the total eclipse. The TGCM calculates the time‐dependent response of the winds, temperature, and mass mixing ratios of the major constituents throughout the thermosphere. Perturbations follow the path of totality, with maximum deviations occurring near 0530 UT at about 350 km. The winds converge from all directions toward the shadow at speeds reaching 60 m s−1 in the upper thermosphere. The maximum temperature anomaly (−70°K) and vertical wind anomaly (−8 m s−1) occur near the center of the shadow. The mass mixing ratio at N2 along a constant pressure surface decreases by up to 2%, and that of O increases by up to 2% in response to the sudden thermospheric cooling caused by the shadow passing over the dayside of the earth. At a constant altitude of 300 km the N2 and O number densities both decrease by about 6%. The time‐dependent calculation shows that disturbances are generated during the onset of the eclipse, with the largest perturbations following the path of totality.