Some characteristic of equatorial spread F at Phu Thuy over a solar cycle

Abstract

This paper presents the research results of the occurrence of equatorial spread F at Phuthuy ionospheric observatory in Hanoi over a solar cycle (1962-1979). The most common type of spread-F observed at Phuthuy are the range spread type (Fs_Q) and the frequency spread type (Fs_F). In both phases, the maximum Fs occurs after midnight (maximum at 1-2 LT). The seasonal variation of Fs occurrence showed peaks at equinox months during the maximum sunspot years, but during the moderate and weak sunspot years there was a peak in summer. Range spread type
occurs concentratively on the before midnight period, on the equinox month and on the maximum sunspot years.
Frequency spread type occurs concentratively on the after midnight period, on the summer and on the moderate and weak solar activily. The characteristic features and the variations of Spread F occurrence at Phuthuy, Hanoi (13.02°N magnetic latitude) are similar from those at Ahmedabad, Indian (15.00°N magnetic latitude).