FIRST OBSERVATIONS OF EQUATORIAL-SPREAD-F FROM INDIAN MST RADAR

The newly established MST radar at Gadanki (13.5 degrees N, 79.2 degre es E) was operated on a few occasions in ionospheric field-aligned bac kscatter mode to investigate the small-scale (similar to 3 m) irregula rities associated with the equatorial spread F. Observations are prese nted of sample Doppler spectra and height-time variations of signal in tensity and weighted mean Doppler velocity. The Doppler spectra are mo stly of the composite type similar to that observed at Jicamarca and a re quite variable both in height and time. The Doppler velocities of t he 3-m irregularities are found to be consistent in general with the s lopes observed of the scattering structures in the height-time-intensi ty plots. The peak signal intensities are found to be as high as 40 dB above the mean noise level, and the peak Doppler velocities are aroun d 70 m s(-1).