Meter size irregularities are routinely studied with radars in the equatorial and low latitude regions. In both instances echoes from the E-region (90 to 120 km altitude) are a common occurrence. The resulting echoes are labeled as so-called Type I or Type II according to their spectral signature. In this paper we show that the phase velocity of Type I echoes increases with decreasing altitude owing to thermal feedback effects taking place in the growth process. We also show that Type II echoes can be influenced by atmospheric neutral winds to the point of revealing the presence of Kelvin- Helmholtz billows, as shown by a recently studied example taken from the Gadanki radar in India.
equatorial electrojet; plasma waves and instabilities; ionospheric irregularities; low latitude E-region; VHF radar spectra; quasi-periodic echoes; Kelvin-Helmholtz billows; turbulence
