Small‐scale (∼3 m) <i>E</i> region irregularities at and off the magnetic equator

Abstract

VHF backscatter radar observations at and off the magnetic equator (Trivandrum and Gadanki, respectively) have been analyzed to study the small‐scale (∼3 m) irregularities at E region altitudes. The Doppler spectra observed at Gadanki invariably resemble type 2 (gradient drift instability) Doppler spectra in contrast to the spectra at Trivandrum where both type 1 and type 2 occur. The type 2 irregularities (at Gadanki) are attributed to the presence of steep (vertical) electron density gradients, which are necessary for the growth of gradient drift instabilities at the off magnetic equatorial latitude of Gadanki. The observed irregularity drifts at lower altitudes (&lt;97 km) are attributed mainly to the meridional neutral winds and those at higher altitudes (&gt;101 km) to magnetic field line‐linked F region electric fields at the magnetic equator.