An analysis of the physical parameters of 5759 faint radio meteors

Abstract

The results of an analysis of about 6000 meteors detected in 1962 from at least three different stations located around Havana, Illinois, under the Harvard Radio Meteor Project are presented. Each station yields instantaneous values of the meteor velocity υ and the electron line density q in the trail, thus permitting the determination of the mean deceleration and a sketch of the ionization curve. From the ionization curve we can compute the meteor mass m∞. It is then possible with the aid of some assumptions to derive values for the density and the ablation coefficient. The mean mass is about 10−4 gram. The mean velocity turns out to be rather low (34 km/sec) and confirms the existence of a systematic shift in the velocity distribution, depending upon the mass of the particles. The dependence of radio magnitudes M (i.e., maximum electron line densities qm) on the basic parameters of meteors (velocity, mass, and zenith angle ZR) turns out to be very close to the predictions of the single-body theory. In fact, we find qm ∼ m∞0.9 υ∞3.9 cos ZR. However, meteors are on the average 1 magnitude brighter than predicted by the same theory and are about one-half shorter in duration and length. Such results are ascribed to the common occurrence of fragmentation. Moreover, the dependence of all three characteristic heights on velocity is much less than expected, there is a very large discrepancy between observed and theoretical beginning heights, and high-velocity meteors appear to ionize much lower than predicted by theory. The median value of the computed densities turns out to be 0.8 g cm−3, pointing out that the structure of radio meteors is as fragile as that of both ordinary photographic meteors and extremely large ones. Mean values of basic parameters for shower meteors do not differ significantly from the corresponding ones for sporadic meteors; thus a result previously obtained for photographic meteors having an average mass of 1 gram is confirmed. This lack of differentiation between sporadic and shower meteors is proof of the cometary origin of most meteors.