Nightside Detection of a Large‐Scale Thermospheric Wave Generated by a Solar Eclipse

Abstract

AbstractThe generation of a large‐scale wave in the upper atmosphere caused by a solar eclipse was first predicted in the 1970s, but the experimental evidence remains sparse and comprises mostly indirect observations. This study presents observations of the wind component of a large‐scale thermospheric wave generated by the 21 August 2017 total solar eclipse. In contrast with previous studies, the observations are made on the nightside, after the eclipse ended. A ground‐based interferometer located in northeastern Brazil is used to monitor the Doppler shift of the 630.0‐nm airglow emission, providing direct measurements of the wind and temperature in the thermosphere, where eclipse effects are expected to be the largest. A disturbance is seen in the zonal and meridional wind which is at or above the 90% significance level based on the measured 30‐day variability. These observations are compared with a first principles numerical model calculation from the Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model, which predicted the propagation of a large‐scale wave well into the nightside. The modeled disturbance matches well the difference between the wind measurements and the 30‐day median, though the measured perturbation (∼60 m/s) is larger than the prediction (38 m/s) for the meridional wind. No clear evidence for the wave is seen in the temperature data, however.