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. Plain Language Summary A total solar eclipse occurred on 21 August 2017 over the UnitedStates 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.

Change in Total Electron Content During the 26 December 2019 Solar Eclipse: Constraints From GNSS Observations and Comparison With SAMI3 Model Results

“…This estimated shadow migration velocity is relatively less as compared to the similarly estimated velocity (0.74 km s −1 , Kundu et al, 2018) during the 21 August 2017 total solar eclipse over the United States. The 2017 total solar eclipse had a faster moving shadow which triggered bow waves, in addition to the TEC depletion by the moon shadow (Eisenbeis et al, 2019). However, in the present case of 2019 annular solar eclipse, the shadow migration velocity is relatively slower which may not have generated the bow waves.…”

First Report of an Eclipse From Chilean Ionosonde Observations: Comparison With Total Electron Content Estimations and the Modeled Maximum Electron Concentration and Its Height

“…Furthermore, Eisenbeis et al (2019), using 3,000 GNSS receivers to determine the TEC, found that a 3-D fast Fourier transform analysis permits the full identification of TIDs generated by an eclipse. They found that these TIDs exhibit wavelengths and periods of 50-100 km and 30 min, respectively, and 500-600 km and 65 min.…”

“…By contrast, Mrak, Semeter, Drob, et al (2018) and Mrak, Semeter, Nishimura, et al (2018) suggested that (a) the TEC observations and modeling results can be explained by the coincidental production of TIDs by tropospheric storm waves that propagate radially from the storm center with a horizontal wavelength of 350 km and a velocity of~200 m s −1 and that (b) the prominent large-scale TEC disturbances are produced by direct EUV modulation due to the inhomogeneity of solar radiation. Furthermore, Eisenbeis et al (2019), using 3,000 GNSS receivers to determine the TEC, found that a 3-D fast Fourier transform analysis permits the full identification of TIDs generated by an eclipse. They found that these TIDs exhibit wavelengths and periods of 50-100 km and 30 min, respectively, and 500-600 km and 65 min.…”

Coordinated Ground‐Based and Space‐Borne Observations of Ionospheric Response to the Annular Solar Eclipse on 26 December 2019

“…Recently, the Great American Eclipse, which passed through the continental United States from northwest to southeast on 21 August 2017, offered a rare opportunity to study the midlatitude ionosphere and thermosphere response in detail with unprecedented dense observational instruments. Besides the above‐mentioned eclipse effects, a number of interesting findings were reported as well, such as large‐scale TEC and NmF 2 depletion for more than 50% (e.g., Cherniak & Zakharenkova, 2018; Coster et al, 2017; Reinisch et al, 2018), traveling ionospheric disturbances and thermospheric wave (e.g., Eisenbeis et al, 2019; Harding et al, 2018; Mrak et al, 2018; Nayak & Yiǧit, 2018; Pradipta et al, 2018; Zhang et al, 2017), enhanced and long‐lasting posteclipse response (e.g., Lei, Dang, et al, 2018; Wu et al, 2018), and topside ionosphere composition change and interhemispheric ion flows (e.g., Perry et al, 2019; Yau et al, 2018).…”