Power Spectra of Equatorial Ionospheric Scintillation at 327 MHz

Abstract

Power spectrum analysis of ionospheric scintillation at the equatorial station Ootacamund (Ooty, 3.4ᵒN dip) using the Ooty radio telescope (at 327 MHz) is presented. All the examined power spectra show power-law high-frequency fall-off; Fresnel oscillations are never detected. The representative nighttime spectral features observed at Ooty at 327 M Hz are given as: Fresnel frequency ~ 0.1 Hz, cut-off frequency ~ 0.3 Hz, and spectral slope ~ 4. A decrease in Fresnel frequency is observed at relatively large pairs of dip and zenith angles, thereby implying anisotropic 'sheet' irregularities in the magnetic meridian. The quasi-theoretical approach of spectral analysis is shown to be limited in its application in the deduction of drift speed and scale size of scintillation-causative irregularities under such geometric propagational conditions.