Mass distribution of meteoroids as determined by radar observations of underdense meteor trails

Abstract

The amplitudes of meteor echoes recorded on high-power radar equipment at Springhill Meteor Observatory have been measured for 57 samples of about 500 meteors each, obtained at various times of day on at least 1 day per month. The number of echoes as a function of echo amplitude is represented by a power law and the exponent in this relation calculated for each sample. Within the limits of error, no strong diurnal or seasonal variations in this exponent have been found. Similarly, there are no significant changes in the exponent when the data are divided into groups according to the height at which the echoes occurred and also according to the distance from the radar to meteor trail.Calibration of the equipment and the methods employed in obtaining and reducing the data are treated in detail. Theory relating the number distribution of echo amplitudes to the distribution of meteoroid masses is reviewed and assessed critically.A best value for the average mass index, s, of the sporadic meteor population in the range from 7th to 10th magnitude is s = 2.3 ± 0.1. The dispersion of individual sample values of s is about ± 0.3.