Review on Ionospheric response to Total Solar Eclipse

The ionospheric dynamics is highly influenced by the solar radiation. During a solar eclipse, the moon occults the solar radiation from reaching the ionosphere, which may drastically affect the variability of the ionosphere. The variability of total electron content (TEC) observed by dual frequency Global Positioning System (GPS) receivers has made it possible to study effects of solar eclipse on the ionosphere. Ionospheric behavior during eclipse was analyzed by using TEC data archived at International GPS Satellite (IGS) stations. TEC variations of few consecutive days are used to study instantaneous changes of TEC during the eclipse event. The results generally show TEC decrease. TEC enhancement and depletion were observed during the totality of the eclipse. Some of the total solar eclipse events were taken into account, i.e.;total solar eclipse of November 3 2013 in Africa and 22 July 2009 in different Indian regions; the study found out that the ionospheric TEC was modified by wave-like energy and momentum transport and obscuration of the solar disc due to the total solar eclipse.The variability of ionospheric response to the total solar eclipse has been studied analyzing the GPS data recorded at the four Indian low-latitude stationsVaranasi (100 % obscuration), Kanpur (95 % obscuration), Hyderabad (84 % obscuration) and Bangalore (72 % obscuration). The retrieved ionospheric vertical total electron content (VTEC) shows a significant reduction (reflected by allPRNs (satellites) at all stations) with a maximum of 48 % at Varanasi (PRN 14), which decreases to 30 % at Bangalore (PRN 14). The reduction in VTEC compared to the quiet mean VTEC depends on latitude as well as longitude, which also depends on the location of the satellite with respect to the solar eclipse path. The amount of reduction in VTEC decreases as the present obscuration decreases, which is directly related to the electron production by the photoionization process. The analysis of electron density height profile derived from the COSMIC (Constellation Observing System for Meteorology, Ionosphere & Climate) satellite over the Indian region shows significant reduction from 100 km altitude up to 800 km altitude with a maximum of 48 % at 360 km altitude. The oscillatory nature in total electron content data at all stations is observed with different wave periods which are attributed to gravity wave effects generated in the lower atmosphere during the total solar eclipse.