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Characteristics of simultaneous VHF (244 MHz) and L-band (1.5 GHz)scintillations recorded at a low-latitude station, Waltair (17.7° N,83.3° E), during the low sunspot activity year of March 2004 to March2005, suggest that the occurrence of scintillations is mainly due to twotypes, namely the Plasma Bubble Induced (PBI), which maximizes during the postsunset hours of winter and equinoctial months, and the Bottom Side Sinusoidal(BSS) type, which maximizes during the post-midnight hours of the summersolstice months. A detailed study on the spectral characteristics of thescintillations at both the frequencies show that the post-sunsetscintillations are strong with fast fading (≈40 fad/min) and aremultiple in nature in scattering, giving rise to steep spectral slopes,whereas the post-midnight scintillations, which occur mostly on the VHF signalwith low fading rate (≈4 fad/min), are of the BSS type, often showingtypical Fresnel oscillations with reduced roll off spectral slopes, indicatingthat the type of irregularity resembles a thin screen structure giving riseto weak scattering. Using the onset times of several similar scintillationpatches across the two satellite (FLEETSAT 73° E, INMARSAT65° E) ray paths (sub-ionospheric points are separated by 82 km), theEast ward movement of the irregularity patches is found to vary from 150 to250 m/s during the post sunset hours and decrease slowly during the postmidnight hours. Further, the east-west extent of the PBI type ofirregularities is found to vary from 100 to 500 km, while that of the BSStype extend up to a few thousand kilometers.  <b>Keywords.</b> Ionosphere (Ionospheric irregularities; Auroralionosphere; Electric fields and currents

VHF and L-band scintillation characteristics over an Indian low latitude station, Waltair (17.7° N, 83.3° E)