On October 24, 1995, and March 9, 1997, two solar eclipse events occur. It is therefore of interest to investigate how the ionosphere responded to the eclipses. Five global positioning system (GPS) ground-based receivers are specifically designed to observe large-scale ionospheric variations over the geomagnetic equatorial, equatorial anomaly crest, and midlatitude regions. Two-dimensional images of ionospheric total electron content (TEC) during the two eclipse periods are constructed. The deviations in the TEC images on eclipse days from those on reference days show that during the eclipse days the ionosphere experienced some large-scale changes. Four features of the TEC deviations, pre-ascension (PA), major depression (MD), sunset ascension (SA), and secondary depression (SD) have been observed. A detailed study shows that in geomagnetic low latitudes, PAs are possibly related to the locations of the equatorial anomaly crest. The latitudinal location, amplitude, and occurrence time of MDs suggest that the fountain effect is essential. SAs and SDs occurring in geomagnetic equatorial and low latitudes and appearing respectively before/around and after local sunset indicate that the prereversal enhancement plays an important role.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999JA900001

Ionospheric total electron content response to solar eclipses

Effects of the August 11, 1999 total solar eclipse as deduced from total electron content measurements at the GPS network

Satellite beacon observations during eclipses have provided much information on the behavior of the ionosphere. A combination of Faraday rotation and differential phase measurements as well as ionosonde data can provide information on the topside and bottomside ionospheric behavior during an eclipse as well as on the production rate. Recent attention has been directed toward a study of the dynamics of the F region during an eclipse and the relation between the amount of depletion in the total electron content and the percent obscuration of the sun. Of particular interest is the time delay from the maximum obscuration to the maximum depletion of the total electron content. Further modeling studies are required in order to reproduce the experimental results. Further observations are also required in order to establish whether TID's are generated following a total solar eclipse as predicted theoretically. In particular, it appears that a more sensitive technique such as differential Doppler rather than Faraday rotation is required. The total solar eclipse of June 11, 1983, with its long totality time of 4–5 min over Indonesia and Papua New Guinea will provide an ideal opportunity for further studies of these unanswered questions.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/RS019i003p00769%4010.1002/%28ISSN%291944-799X.BEACSAT1

The study of the effect of solar eclipses on the ionosphere based on satellite beacon observations

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018JA025566

Global Responses of the Coupled Thermosphere and Ionosphere System to the August 2017 Great American Solar Eclipse

Previous studies have been devoted to examining the ionosphere and thermosphere response during the solar eclipse, but the posteclipse response of the global ionosphere and thermosphere has not been well quantified. In this study, for the first time, we quantitatively investigate the posteclipse response of the global ionosphere and thermosphere system to the recent Great American Solar Eclipse using a high-resolution, global, coupled ionosphere-thermosphere-electrodynamics model. It was found that the posteclipse response of the ionosphere and thermosphere is significant and worldwide, which was not expected. Specifically, even 9 hr after the eclipse ended, the globally averaged ionospheric total electron content perturbations were about 0.2 total electron content unit, and the corresponding changes in neutral temperature and winds reached 2 K and 2 m/s. The changes in the global dynamic and energetic processes associated with the solar eclipse contributed to this long-lasting response of the ionosphere and thermosphere during the posteclipse period. Plain Language Summary The thermosphere is the layer of the Earth’s atmosphere above the mesosphere between about 60 and 1,000 km, and the ionosphere is the ionized part of the atmosphere. In this region, the neutral gas and the ionized plasma have significant impact on low Earth orbiting determination and satellite radio communications. This work is the first to use a state-of-the-art, first-principles model of the coupled thermosphere and ionosphere, with self-consistent electrodynamics, to systematically investigate the dynamics and electrodynamic behavior of the global ionosphere and thermosphere after an eclipse. Although the solar eclipse is a transient local event, its impact on the ionosphere and thermosphere can persist for a long time over the entire globe, rather than just being an impulse event with a localized response as was previously expected. This effort paves the way for improving the understanding of the upper atmospheric variability.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018JA025460

Demertrius Matsoukas

Papers

Electron content measurements by beacon s-66 satellite during the may 20, 1966, solar eclipse.