Short- and Long-Wavelength TIDs Generated by the Great American Eclipse of 21 August 2017

Abstract

On the 21 August 2017 the eclipse shadow drastically changed the state of the ionosphere over the United States. This effect on the ionosphere is visible in the total electron content measured by Global Navigation Satellite Systems (GNSS). The shadow moved with the supersonic speed of ~1,000 m/s over Oregon to ~650 m/s over South Carolina. In order to exhaustively explore the ionospheric signature of the eclipse, we use data of total electron content from ~3,000 GNSS stations seeing multiple Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) satellites to visualize the phenomena. This tremendous dataset allows high-resolution characterization of the frequency content and wavelengths—using an omega-k analysis based on 3-D fast Fourier transform—of the eclipse signature in the ionosphere in order to fully identify traveling ionospheric disturbances (TIDs). We confirm the generation of TIDs associated with the eclipse including TIDs interpreted as bow waves in previous studies. Additionally, we reveal, for the first time, short (50–100 km) and long (500–600 km) wavelength TIDs with periods between 30 and 65 min. The sources of the revealed short wavelength TIDs are co-located with the regions of stronger gradient of the EUV related to sunspots. Our work confirms and describes physical properties of the waves observable in the ionosphere during the Great American Eclipse.