| Autor: |
Eisenbeis, J., Occhipinti, G., Astafyeva, E., Rolland, L. |
| Zdroj: |
Journal of Geophysical Research - Space Physics; November 2019, Vol. 124 Issue: 11 p9486-9493, 8p |
| Abstrakt: |
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. A total solar eclipse occurred on 21 August 2017 over the United States with the eclipse shadow reaching supersonic speed. We calculate the differential total electron content to visualize the evolution of the phenomena with incredible high spatial and temporal resolution. Traveling ionospheric disturbances associated with the eclipse with a period of up to 1 hr and wavelengths of 40 to 600 km including bow waves with a period of ~25 min and wavelength of ~300 km are identified using an omega‐k analysis based on 3‐D fast Fourier transform. The additionally highlighted shortest (50–100 km) and longest (500–600 km) wavelength traveling ionospheric disturbances have not been observed before. The shortest waves seem to be related to sunspots. GNSS observations of solar eclipse show differential total electron content (dTEC) depletions reaching −0.4TECU in the path of totalityWe observe longer wavelength TIDs that are related to the TEC depletion due to the Moon's shadow, as well as shorter wavelength TIDsThe omega‐k analysis using 3‐D FFT allows to highlight the characteristics of the main and more energetic generated TIDs and bow waves. |
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