The F-scatter phenomenon and the drift of small-scale irregularities in the low-latitude nighttime ionospheric F-region

The drift of small-scale irregularities (SSIs) was observed with the D1 technique at the Tbilisi station during periods of weak frequency-type F-scatter. The SSIs in the low-latitude nighttime F-region were found to have an elliptical shape with an anisotropy axis oriented predominantly along the geomagnetic field. Irregularities drift toward the southwest with velocities of 40-100 m/s.