Characteristics of low latitude ionospheric E-region irregularities linked with daytime VHF scintillations measured from Varanasi

VHF amplitude scintillations recorded during the daytime period from January 1991 to December 1993, April 1998 to December 1999 and January 2008 to December 2008 at low latitude station Varanasi (geographic lat. = 25A degrees 15'N; long. = 82A degrees 59'E; geomagnetic lat. = 14A degrees 55'N, long. = 154A degrees E, dip angle = 37.3A degrees, sub-ionospheric dip = 34A degrees) have been analyzed to study the behaviour of ionospheric E-region irregularities during the active solar and magnetic periods. The autocorrelation functions, power spectral densities, signal de-correlation times are computed to study the temporal features of ionospheric E-region irregularities linked with daytime scintillations. Derived spectral index ranges between -2 and -9. Assuming velocity of irregularities, the characteristic lengths of the E-region irregularities are estimated. We have estimated the minimum and maximum range of scale length of sporadic-E (E (s) ) irregularities to be observed over Varanasi. These results are in close agreement with those reported from this latitude region.