Meteoroid streams and meteor showers

Abstract

This chapter discusses the stages involved in the evolution of meteoroid streams and meteor showers. Solid particles (meteoroids) are lost from a comet as part of the normal dust-ejection process. Small particles are driven outward by radiation pressure but the larger grains have small relative speed, much less than the orbital speed. Thus, these meteoroids move on orbits that are slightly perturbed from the cometary orbit. The generally accepted evolution of meteoroids following ejection from a comet may be described in four steps: (1)spreading about the orbit because of the cumulative effects of a slightly different orbital period, (2) a spread in the orbital parameters because of gravitational perturbations, (3) a decrease in size because of collisions and sputtering, all in due course leading to a loss of identity as a meteor stream and thus becoming part of the general sporadic background, and (4) reduction in both semi-major axis and eccentricity producing particles of the interplanetary dust complex caused by Poynting–Robertson drag.