The above-cited works signify the fact that the response of the ionosphere to the solar eclipse depends on various factors such as geophysical condition, longitude, latitude, and local time. have observed 20% TEC decrement at polar sector. For the total solar eclipse that happened on November 23, 2003, Rashid et al. showed the depression of TEC to be more than 40%–50% relative to quiet-time TEC level. have reported it to be of the order of about 0.2–0.3 TECU over midlatitudes. In terms of change in magnitude of TEC, some studies reported depression of TEC to be about a few TECU, whereas Afraimovich et al. Many reported results suggest that the depression in TEC growth during the eclipse is almost independent of longitude and latitude, whereas some works reported that the decrease in the TEC is dependent on the geomagnetic latitude (e.g., 49). However, latitudinal and longitudinal dependence of decrement in TEC is still under debate. A delay in GPS signal during eclipse may possibly be due to the combined effect of the photochemical processes and plasma dynamics in EIA regions. The delay in GPS signal may reach as long as 2 h from the hour of greatest obscuration (e.g., Yeh et al.

This corresponds to 0–30 min time delay in GPS signal. For example, a decrement in TEC of the order of 7 TECU over EIA and at midlatitude region of Asia during the solar eclipse events of October 24, 1995, and March 9, 1997, has been reported. Thus, TEC provides accurate information about the total ionization loss. The irregular horizontal gradients affected by the eclipse complicate phase ambiguity resolution in precise GPS measurements.Īs has been noted earlier, TEC is the integral measure of the vertical ionospheric electron density thus, during a solar eclipse, TEC gives data about the total ionization loss of the ionosphere as a consequence of the diminished photoionization. Since production of ionosphere is directly related to solar radiation during daytime, the shadow of the Moon decreases the ionizing radiation from the Sun during a solar eclipse, and this ultimately produces errors in GPS signal. An annular eclipse happens when the Moon is near its apogee of the Earth and looks to some degrees minute than the Sun. An eclipse that happens when the Moon is close to its perigee of the Earth can be a total eclipse, and the Moon will land to be sufficiently enormous to cover completely the Sun's photosphere.

Solar eclipse is a celestial occasion during which the Moon intrudes between the Sun and the Earth and the Moon absolutely or generally covers the Sun. Singh, in GPS and GNSS Technology in Geosciences, 2021 1.4 Solar eclipse

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