DYNAMICAL MODEL FOR THE ZODIACAL CLOUD AND SPORADIC METEORS

Abstract

The solar system is dusty, and would become dustier over time as asteroids\ncollide and comets disintegrate, except that small debris particles in\ninterplanetary space do not last long. They can be ejected from the solar\nsystem by Jupiter, thermally destroyed near the Sun, or physically disrupted by\ncollisions. Also, some are swept by the Earth (and other planets), producing\nmeteors. Here we develop a dynamical model for the solar system meteoroids and\nuse it to explain meteor radar observations. We find that the Jupiter Family\nComets (JFCs) are the main source of the prominent concentrations of meteors\narriving to the Earth from the helion and antihelion directions. To match the\nradiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar\n(CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets,\nand JFCs in particular, must frequently disintegrate when reaching orbits with\nlow perihelion distance. Also, the collisional lifetimes of millimeter\nparticles may be longer (>10^5 yr at 1 AU) than postulated in the standard\ncollisional models (10^4 yr at 1 AU), perhaps because these chondrule-sized\nmeteoroids are stronger than thought before. Using observations of the Infrared\nAstronomical Satellite (IRAS) to calibrate the model, we find that the total\ncross section and mass of small meteoroids in the inner solar system are\n(1.7-3.5)x10^11 km^2 and 4x10^19 g, respectively, in a good agreement with\nprevious studies. The mass input required to keep the Zodiacal Cloud (ZC) in a\nsteady state is estimated to be 10^4-10^5 kg/s. The input is up to 10 times\nlarger than found previously, mainly because particles released closer to the\nSun have shorter collisional lifetimes, and need to be supplied at a faster\nrate.\n