Ionospheric effects of the 2017 US Eclipse

Just in time for the approaching eclipse Huba and Drob have published a simulations of the ionospheric effects of the eclipse modeled using the SAMI3 model. The study appeared in late June in Geophysical Research Letters. The plain language summary of the study is as follows:

"We use the first-principles ionosphere/plasmasphere model Sami3 is Also a Model of the Ionosphere to predict the impact of the upcoming total solar eclipse traversing the continental United States on 21 August 2017. We find that the reduction in solar radiation reaching the Earth has a significant impact on the Earth’s ionosphere: the electron density can decrease by almost a factor of 2 in the F region between 150 and 350 km, and the electron temperature can decrease by 15% at higher altitudes. Moreover, we find that the reduction in the electron density affects the electrical conductance of the ionosphere which modifies the global electric field in the American sector. This can modify the Earth’s ionosphere in the magnetically conjugate region at the tip of South America which should be observable."

Change in vertical total electron content at 18:36 UTC, August 21st 2017 due to eclipsed ionosphere. Conjugate effects can be also seen on the opposite hemisphere at the magnetically conjugate ionosphere. From: Huba and Drob (2017). 

The map of vertical TEC can be measured relatively well nowadays with a global network of GNSS receivers, which observe line integrated electron density between the receiver and the fleet of GNSS satellites. In the US sector, there are thousands of receivers that can be used. It will be interesting to see how the observations compare with the prediction. The predicted 5 TEC unit reduction in TEC is definitely observable, as the errors in absolute vertical TEC are of the order of 0.3 TEC units, and the relative errors for any given receiver-satellite path much less than this. It will be interesting to see if there are secondary effects, such as lower atmosphere neutral atmosphere effects, which propagate into the ionosphere.


Huba, J. D., and D. Drob (2017), SAMI3 prediction of the impact of the 21 August 2017 total solar eclipse on the ionosphere/plasmasphere system, Geophys. Res. Lett., 44, 5928–5935, doi:10.1002/2017GL073549.