Symposium: Astrometry I: The steady-state space distribution of meteoric particles under the operation of the Poynting-Robertson Effect
A model is proposed for the distribution of interplanetary meteoric particles that is based upon orbital data from observed meteors and upon comparisons with zodiacal light. Orbits obtained from a random sam- ple of photographic meteors are used to construct a distribution function for the number of meteoric particles continuously injected into the solar system. The Poynting-Robertson effect is then introduced with the result that every particle must ultimately be destroyed by a close approach to the sun. The resulting steady- state distribution of orbits is derived, and from it relative values of the space density of particles are com- puted at many points in the solar system. Absolute values of the space density are determined by comparison of zodiacal-light observations with the theoretical apparent brightness of the system of particles due to scattered sunlight. Brighter portions of the zodiacal light are well reproduced with either of the two scatter- ing laws used. Both laws include a diffraction term; one law also produces a gegenschein effect. Numerical results at the earth's distance are found to be in substantial agreement with recent density estimates by Ingham. Particles in the 1 to 50 p range play the dominant role in the scattering of light. Their average albedo is 0.12, and their surfaces are somewhat smoother than that of asteroidal material.