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.

The Dust in the Coma of Comet Halley

“…We summarise the conclusions from Greenberg and Hage (1990), which were based on a broader discussion: a high coma dust porosity of 0.93 < P < 0.975 is a likely possibility which is consistent with (a) the direct results of this work, (b) comet densities as deduced independently by other workers (Sagdeev et al 1988, Sekanina andYeomans 1985) and (c) observed meteor densities (Verniani 1973). Furthermore, there are two additioanl features in the present model of comets which are critical'm producing the observed 9.7 fim and 3.4 \xm coma dust emissions: (1) The presence of organic refractory material.…”

Dynamical Model for the Toroidal Sporadic Meteors

“…Masses are computed by calculating the electron-line density q of the echo based on its received power, location in the radar beam and range. The mass-velocity-ionization relation of Verniani (1973) is then used to convert from q to m. Particles smaller than ∼200 μm were not detected in the NT source because their typical impact speeds make the ionization factor I smaller than I . Indeed, we observe a strong D versus V correlation whose low-end closely follows the I I 1 limit.…”

Ondřejov radar observations of Leonid shower activity in 2000–2002

“…To relate the meteor overdense duration, T , to the mass of a meteoroid we have used the formula for maximum electron line density, α max , as a function of the meteoroid mass, M ∞ , its velocity, V, and radiant position embodied by the zenith distance, z r , which had been published by Verniani (1973) α max = 2.73 × 10 10 M 0.92…”