Behaviour of the ionospheric layers at Ahmedabad during the sunrise period

Abstract

A detailed analysis of the sunrise effect on the ionospheric layers at Ahmedabad (23°02'N, 72°34'E) over a period of one solar cycle (1953-1964) has been presented in this article. The sunrise effect in F2 is observed at about 100 km sunrise during winter and equinoxes while during summer it is delayed approximately by half an hour from 100 km sunrise time; however it occurs always before ground sunrise. Sunrise effect in E2-layer has been observed always about 15 min before ground sunrise. The effect in E-layer takes place about half an hour after ground sunrise and in F1-layer one and half hour after ground sunrise. It is found that around pre-dawn period there is an excessive increase in thickness of the F-layer followed by splitting into two layers the lower one at about 150 km and the upper one at about 300 km. The phenomena connected with movements and tilts in the ionosphere are observed during the early morning hours.