SMALL-SCALE (SIMILAR-TO-3M) E-REGION IRREGULARITIES AT AND OFF THE MAGNETIC EQUATOR

VHF backscatter radar observations at and off the magnetic equator (Tr ivandrum and Gadanki, respectively) have been analyzed to study the sm all-scale (similar to 3 m) irregularities at E region altitudes. The D oppler spectra observed at Gadanki invariably resemble type 2 (gradien t drift instability) Doppler spectra in contrast to the spectra at Tri vandrum where both type 1 and type 2 occur. The type 2 irregularities (at Gadanki) are attributed to the presence of steep (vertical) electr on density gradients, which are necessary for the growth of gradient d rift instabilities at the off magnetic equatorial latitude of Gadanki. The observed irregularity drifts at lower altitudes (<97 km) are attr ibuted mainly to the meridional neutral winds and those at higher alti tudes (>101 km) tp magnetic field line-linked F region electric fields at the magnetic equator.