The Size–Frequency Distribution of the Zodiacal Cloud: Evidence from the Solar System Dust Bands

Recent observations of the size–frequency distribution of zodiacal cloud particles obtained from the cratering record on the LDEF satellite are the latest evidence for a significant large particle population (100-μm diameter or greater) near 1 AU. Our previous modeling of the Solar System dust bands, features of the zodiacal cloud associated with the comminution of Hirayama family asteroids, has been limited by the fact that only small particles (25-μm diameter or smaller) have been considered. This was due to the prohibitively large amount of computing power required to numerically analyze the dynamics of larger particles. The recent availability of inexpensive, fast processors has finally made this work possible. Models of the dust bands are created, built from individual dust particle orbits, taking into account a size–frequency distribution of the material and the dynamical history of the constituent particles. These models are able to match both the shapes and amplitudes of the dust band structures observed by IRAS in multiple wavebands. The size–frequency index, q, that best matches the observations is approximately 1.4, a distribution in which the surface area (and hence the infrared emission) is dominated by large particles. However, in order to successfully model the “ten degree” band, which is usually associated with collisional activity within the Eos family, we find that the mean proper inclination of the dust particle orbits has to be approximately 9.35°, significantly different from the mean proper inclination of the Eos family (10.08°).