Meteoric storms and formation of meteor streams

Abstract

AbstractMeteoric storms must be very young formations, since planetary perturbations disperse any dense cloud of meteoroids within several revolutions around the sun. It is shown that, by comparing the dates of appearances of the storms of a meteor stream with the return dates of the parent comet, insight can be gained into the problem of the origin and early evolution of such a stream. Applying a recent theory of particle ejection from comets, we have developed a formula relating the character of motion of a cloud of meteoroids to the circumstances of ejection.Practical application of the method to the Leonid, Perseid and η-Aquarid storms indicates low mass density of cometary meteoroids (not more than 0.3 g/cm3), ejection velocities of tens to hundreds of meters per second (with water vapor as the drag force), and suggests that meteoroids are ejected from periodic comets predominantly after perihelion. This finding contrasts with observational evidence of the type II tails of ‘new’ dust-rich comets. It is concluded that the discrepancy may actually reflect structural differences between the ‘new’ and periodic comets.