S band scintillations studies near the EIA crest of Indian zone

Abstract

The results of statistical and morphological studies of ionospheric scintillation data at S band (2492.08 MHz), still unexplored, in conjunction with those at L5 (1176.45MHz) and VHF (250.650 MHz) band for the period of 2015–2016 are presented. The observations are carried out at Raja Peary Mohan College center (RPMC: 22.660 N, 88.40 E) situated near the northern crest of the equatorial ionization anomaly (EIA). The morphological studies on the occurance features at multi-frequency bands with SI>3dB level exhibit a decreasing trend with 10.7cm solar flux. Much less occurrence in S band compared to VHF as well as L5 band reflects the frequency dependent features. S band scintillations are mainly observed in the equinoctial months of high solar epochs while at the lower frequency VHF/L5 bands occurrences are recorded in the solstitial months also. During the periods of severe scintillations frequent losses of lock in the L5 channel is recorded. The maximum fade rate is observed in the middle of the patch irrespective of frequency. The study of cumulative amplitude distribution dictates a fade margin of 14 dB in L5 band and 8–9 dB in S band respectively. Power spectral studies of weak scintillation at VHF, L5 and S band reveals the general features of flat low frequency part and roll off around Fresnel frequency. In the strong scintillation conditions two component spectra dominates the VHF and L5 band while S band spectra always exhibits single component. With the increasing strength of scintillation prominent broadening of spectra in all frequency bands are reflected. During the period a good correspondence between the decorrelation time (τ) and perturbation strength as expressed by S 4 index at S band is evident. Multiple scattering appears to be dominating mechanism for strong scintillation at VHF and L5 band while in S band weak scattering is the primary contributing factor.