Abstract:
From an analysis of ionogram data of Kodaikanal (dip 3.5 deg N) for a 3-yr period of high sunspot activity, it is shown that the duration of equatorial spread-F (ESF), on the average, bears a direct relationship to the peak amplitude as well as duration of the post-sunset enhancement in F-region upward vertical drift in all seasons. The duration of ESF is also found to exhibit a significant positive correlation with the altitude of bottomside F-region at the time of onset of ESF but only during equinoxes and northern winter (D) months.