First observations of type-1 sporadic E irregularities in the equatorial anomaly region using the Chung-Li VHF radar

In this paper we present the characteristics of mid-latitude irregularities first observed with the 52 MHz Chung-Li radar. Intense type-1 echoes with Doppler velocities of about 270 m/s (slightly smaller than the nominal ion-acoustic wave speed of 360 m/s) in the height range from 103.1 km to 104.5 km lasted for about 2 minutes. The range-time variations of sequential power spectra indicate that the patch of type-1 irregularities moved toward the radar at a rate of about 42 m/s. The zonal drift motions of the type-1 and type-2 irregularities obtained from an interferometry technique showed that the irregularities drifted eastward with an average speed of 84 m/s.