Head echoes and solar activity in the geminid period

The occurrence of head echoes in dependence on solar activity in the Geminid period 1959-1969 is examined. All considerations refer to the interval 22sup(h)-06sup(h) U.T. Solar ionizing radiation is assumed to be either X-ray and ultraviolet, or corpuscular radiation. The former is characterized by the correlated solar microwave flux F, and the latter by Asub(p) and Ksub(p) indices. A comparison of the variations with solar longitude of the indices and of relative head echo rates on the days of observation is not possible for every year. A comparison within the 11-year solar cycle does not lead to the conclusion that in the interval 22sup(h)-06sup(h) U.T. it is the corpuscular radiation that determines the head echo phenomenon. A definite answer to the question of the nature of effective radiation will be possible when radar observations for more solar cycles and a longer time interval are available. (author)