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Data from ionosonde and global positioning system (GPS) total electron content (TEC) observations reveal a number of ionospheric phenomena during the total solar eclipse on 21 August 2017 over North America. The eclipse started over the West Coast at similar to 16:00 UTC (similar to 07:53 LT) and ended over the East Coast at similar to 20:00 UTC (similar to 14:46 LT). We identify a growth of plasma density irregularities and turbulence on the bottomside ionosphere during the eclipse totality (at similar to 10:03 LT over Idaho Falls), signified by the distinct appearance of spread-F echoes in the ionosonde data. In addition, data from the ionosonde observations also show some characteristic signatures of traveling ionospheric disturbances at similar to 300-km altitude during the eclipse. Finally, large reductions in TEC and ionospheric plasma densities (by 33-45%) due to the eclipse were observed in both the GPS TEC and ionosonde data.

Plain Language Summary We studied the effects of the 21 August 2017 total solar eclipse on the ionosphere over North America using ionosonde and GPS observations. The ionosphere experienced some degree of plasma density and total electron content reductions during the eclipse, and some of these reductions happened with certain time delay relative to the moment of maximum eclipse. Furthermore, the ionosonde observations indicate that ionospheric plasma over Idaho became turbulent around the moment of eclipse totality and some wave disturbances were also seen in the data shortly after the totality. This type of ionospheric turbulence, referred to in the ionospheric science community by the name spread-F, is more commonly observed during the evening hours. Spread-F is typically much stronger in intensity over the equatorial regions, when compared to spread-F cases over midlatitude regions. The experimental data thus suggest that the solar eclipse can create a favorable condition for spread-F turbulence to appear over a midlatitude location.