Collision frequency of electrons in the F region

Abstract

The collision frequency of electrons in the F region of the ionosphere has been measured at Delhi (geographical latitude 28°38′ N, geographical longitude 77°13′ E) using a method similar to that suggested by Appleton. The amplitude and group path of short radio waves vertically incident on the F region of the ionosphere have been measured simultaneously at a suitable frequency (for both the ordinary and extraordinary wave modes) in early morning and late evening hours, corresponding to times of appearance and disappearance of the echo, respectively. Simultaneous changes in amplitude and group path are related to deduce the collision frequency. Some selected records taken near the time of sunrise have been analyzed and the values of collision frequency are found to be (4.2 ± 0.5) × 103 and (3.5 ± 0.5) × 103 s−1 for the ordinary and extraordinary waves, respectively, in the true-height range of 270–310 km.