Radio echo observations of the Giacobinids meteors, 1946

Abstract

(1) Observations were made of the Giacobinid meteor shower 1946 on a wave-length of 4.2 m. A narrow beam directional aerial was constructed and used for this work. (2) A continuous watch was maintained for 71 hours between 1946 October 8–11. The whole activity of the shower occurred between October 10 ^d 0 ^h –6 ^h U.T. The maximum was extremely sharp and occurred at 10 ^d 40 ^m ±3 ^m , when the echo rate was 168 per minute for the equipment used. (3) A method of obtaining the size distribution of these meteors is described, based on the theoretical work of Herlofson. For the range of meteor sizes studied the numbers of meteors were inversely proportional to the size. (4) Coincident visual observations were obtained for twenty-one echoes. The correlations are similar to those obtained for the Perseid shower 1946. The number of electrons produced per cm. path for these meteors is calculated and shown to be in good agreement with Herlofson's theory. (5) An experiment is described in which the aerial beam was directed into the radiant ; the number of echoes immediately decreased to about 4 per cent of their previous value. (6) The height distribution, durations and amplitudes of the echoes are discussed. Changes in these indicate that the shower may have changed in character as it progressed.