Occurrence characteristics of ionospheric irregularities over Indian low-latitude region varanasi during ascending phase of solar cycle 24

Abstract

Ionospheric irregularities degrade the performance of radio techno-logical system by producing fluctuations in amplitude and phase of signal passing through them, a phenomenon which is known as scin-tillation. This study presents diurnal and seasonal variations of iono-spheric irregularities during ascending phase of solar activity from 2009 to 2014 by using the amplitude scintillation index S4 computed from a dual frequency GPS receiver installed at the low-latitude station of Varanasi (Lat. 25.31° N, Long. 82.97° E). Scintillation occurrences are found to be higher during nighttime hours (1930-0130 LT), and characterized by an equinoctial maximum throughout the years 2009-2014, except for the peculiar solar minimum year 2009. Gravity wave seed perturbation from lower atmosphere and pre-reversal en-hancement (PRE) in zonal electric field have been considered to explain the observed seasonal occurrences, which have been also compared with previous results obtained from observations and model. Influence of solar activity on scintillation occurrence has also been studied, and it was found that there is linear dependence between the solar activity and scintillation occurrence, which is seasonally variable.