Radio echoes and cosmic ray showers

It is suggested that the origin of some of the transient ionic clouds, generally assumed to be responsible for the low level sporadic radio reflexions, may be due to large cosmic ray showers. It is shown that cascade cosmic ray showers of sufficient energy to produce some of these radio reflexions certainly exist, but there is insufficient published evidence to decide whether any of the echoes already observed are actually due to such showers. More conclusive evidence could be obtained from the frequency-size distribution of the radio echoes observed from a horizontal or vertically directed beam.