A note on the meteoric head echo occurrence

Meteoric head echo statistics based on the Perseid observations carried out by the high-power meteor radar at the Springhill Meteor Observatory in the period 1957–1982 are dealt with. A total of 1945 head echoes was recorded during 271 h covering the central part of the Perseid activity in the interval of solar longitudes 139.5° ⩽ L⊙ ⩽ 140.10 (eq. J2000.0). The rate of their occurrence shows an irregular diurnal variation with a minimum near upper culmination of the shower radiant. The ratio of the head echo rate to overdense echo rate having durations T ⩾ 1 s varies from 2.1% at 17 h 30 m LT to about 5.0% at 22 h LT. Attention was paid also to the delay of a secondary echo appearing after the head echo. The maximum delay appears at 5 h 30 m LT and coincides with the lower culmination of the Perseid radiant when the mean delay represents some 2.5 s while its minimum value of 0.05 s coincides with the upper culmination at 17 h 30 m LT.