Ionospheric effects of the August 11, 2018, solar eclipse over the People’s Republic of China
Authors: Chernogor L.F. , Milovanov Y.B. 
Published: November 2020

The purpose of the work is to describe the ionospheric effects of the August 11, 2018 partial solar eclipse (SE) that occurred over the People’s Republic of China, as observed via GPS technology. SEs present rare phenomena of nature. In the course of 2 to 3 hours, the rearrangement of processes acting at the Earth’s surface, in the atmosphere, geospace, i.e., in the Earth — atmosphere — ionosphere — magnetosphere system (EAIMS), occurs. The response of this system depends on the solar activity, season, time of day, and on the state of atmospheric and space weather. Therefore, the study of the EAIMS response to SEs remains an urgent need. The response is accompanied by controllable dynamic processes, the study of which improves our understanding of the near-Earth environment. The study of the EAIMS response to SEs is of fundamental importance to science. Its practical applications include the following. The SE give rise to significant perturbations in the EAIMS, which affect the propagation of radio waves virtually in all frequency bands, and consequently deteriorate the operation of radar, radio astronomy, and radio navigation systems, as well as the instruments for remotely sensing the medium. The SE effects have been studied for over more than about 100 years. Thus far, the following regular effects have been quite well studied: decreases in the electron density, electron and ion temperatures, variations in ion composition, and plasma vertical movements. The irregular effects have been studied to a significantly smaller degree, and they can vary from one solar eclipse to another. The main feature of the SE over the PRC was the fact that it was observed during before local time sunset period. The maximum phase of the eclipse within the PRC area varied from 0.07 to 0.52, while the Sun’s surface area occulted by the moon was observed to be 0.02—0.42. The beginning of the eclipse over the PRC was observed to occur in the 09:54—10:05 UT period, and the end varied from 10:07 UT to 11:10 UT. The SE duration varied from a few minutes to approximately 67 min. The insignificant duration of the eclipse and the dusk terminator affected the SE effects. The state of space weather during the solar eclipse was conducive to observing the SE effects occurring in the ionosphere. To reveal the ionospheric response to the August 11, 2018, SE, the global navigation satellite system data were processed. The ionospheric time delay and, respectively, the vertical total electron content (TEC), were calculated combining the pseudo range and integrated phase data at two frequencies. Regardless of the dusk terminator influence, we have managed to confidently detect the ionospheric SE effects, which proved to be sufficiently small because of small values of the SE phase. Over the People’s Republic of China area, a funnel-shaped decrease in TEC was observed to occur approximately 1,300 km in latitude and 2,000 km in longitude. The TEC decrease was observed to be 7 %. The solar eclipse was accompanied by the generation of aperiodic TEC disturbances at a rate of 0.4—0.8 TEC unit/h and 105-min in duration. Wave disturbances caused by the SE were not observed confidently, which is due to the small value of the SE phase and insignificant disturbances in the electron density.