Multistation analysis of VHF radio wave scintillations at low latitudes

Abstract

Simultaneous observations.of VHF-ionospheric scintillations at Bhopal, Varanasi and Agra, during the period (January 1991-December 1991) have been reported. Nocturnal variation .of.occurrence of scintillations is found to be higher at Bhopal as compared to that at Varanasi and Agra. Under the geomagnetic disturbances the scintiIlations are suppressed in pre-midnight period at all the three stations. Severity .of suppression is found to be more at Bhopal. The storms with the <i>D</i>_st value below - 100 nT, reaching in local nighttime or in very early morning hours are found to be most effective in giving rise to the scintillations in post-midnight period. The results have been interpreted in terms of (i) F-region irregularities associated with spread-F and (ii) coupling of high latitude and magnetospheric current systems with equatorial electric field.