HF backscatter observations of sporadicEduring the IQSY

Observations of sporadic-E activity have been carried out during the IQSY from the United Kingdom using a fixed-frequency, swept-azimuth oblique backscatter sounder operating at 17 Mc/s. Ground scatter by means of sporadic-E ionization was presented on a P.P.I. display and recorded on 16-mm film. Analysis of the film data has shown that, in the north temperate latitudes, Es occurrence for ƒEs > 4 Mc/s is predominantly a daytime phenomenon with a well-defined peak at the summer solstice. The enhanced activity in summer was characterized by both an increase in the occurrence of Es patches with ƒEs > 4 Mc/s having enhanced electron content and by an increase in the number of such long duration clouds. The azimuthal distribution of the observed activity has been shown broadly to be in accord with the differential land-sea backscatter; although some deviations from that expected from previous surveys of temperate latitude behavior are indicated. A low occurrence of Es activity was generally correlated with magnetically disturbed days. Examination of the individual Es clouds has indicated a most probable patch size of 127 km and a most probable velocity of about 30 m/sec. The directions of motion of clouds showed some preference to the WSW.