Fig. 5

The longitude–latitude maps of electron density at an altitude of 300 km obtained from the F7/C2 GIS data during 0430–0830 UT, (a, c, e, g, i) the average electron density during the previous 5 days as reference. (b, d, f, h, j) the electron density on 15 January 2022. The white dotted line denotes the magnetic equator and the shaded region corresponds to the post-sunset period. The blue and green curves denote the sunset terminator in the E- and F-regions, respectively