Meteor Height Distributions and the Fragmentation Hypothesis

Abstract

This paper is concerned with a comparative study of the incidence of fragmentation amongst bright and faint meteors, as disclosed by photographic measurements of heights and light curves of brighter meteors (visual magnitudes < +4), and by measured radioecho height distributions of faint meteors (visual magnitudes ~+6). The discussion is based on photometric and height data for sporadic and shower meteors obtained by Harvard and Canadian observers, and on radio-echo height distributions measured at J odrell Bank. Mean photographic light curves are shorter than predicted by evaporation theory, and there is a large residual scatter in the heights of maximum brightness after reduction to standard meteor velocity and brightness. Trail length is independent of reduced height, and also of velocity if this exceeds 25 km/sec; for slower meteors trail lengths shorten rapidly. The radio·echo height distribution as a function of trail length is calculated for a simple model which incorporates these features of the ablation process for brighter meteors. Comparison with radio height measurements indicates that meteors below the photographic threshold show a closer approach to the predictions of the evaporation theory than meteors bright enough to record photographically.