The theoretical length distribution of ionized meteor trails

Abstract

The lengths of the columns of ionization formed by meteors are determined theoretically from the available theoretical and experimental information on 1. (1) the production and radio detection of meteoric ionization, 2. (2) the mass distribution of shower and sporadic meteors, and 3. (3) the distribution of sporadic meteor radiants. The primary factors controlling the length of an individual meteor trail are the mass of the meteoric particle and its angle of approach (radiant) into the upper atmosphere. The most likely (modal) value of trail length for meteors from the same radiant is found to be 12 sec ζ km for sporadic meteors, and approximately 17 sec ζ km for shower meteors, where ζ is the zenith angle of the radiant. The distribution of sporadic trail lengths is found to be relatively insensitive to the exact radiant distribution. For a representative radiant distribution, the most likely trail length for sporadic meteors is 15 km. When these trails are detected by a radar system, there is a selection process which favours the longer trails, so that the most likely length of the trails detected by a radar system employing a broad-beam antenna is about 25 km. This value compares well with a previous experimental determination of trail lengths. The theory indicates that the length distribution of detected trails is essentially independent of the sensitivity of the radar receiver and the power output of the radar transmitter.