MAGNETOSPHERIC EFFECTS ON MICROMETEOROID FLUXES

The planets, and their moons and rings, are bombarded by a population of interplanetary and interstellar micrometeoroids. This bombardment a ffects the evolution of planetary rings and electron densities in iono spheres. It also generates and overturns regolith on planetary satelli tes and ring particles. The impacting flux is enhanced by the planet's gravity, but the magnetosphere can also affect the flux for micromete oroids near 1 mu m in radius. We present calculations for micrometeoro ids hitting Jupiter which show the magnetosphere shields the planet fr om impactors smaller than about 0.1 mu m in radius, and enhances the f lux of impactors by a factor of up to about 4 for grains near 0.5 mu m in radius. Thus, in addition to the gravitational focusing factor, th ere is a size-dependent electromagnetic focusing factor active up to a bout 1.0 mu m. In addition, we find that after 1 (Earth) year, signifi cant numbers of small particles still orbit Jupiter. The fate of these particles may represent an additional enhancement of the flux of micr ometeoroids onto the planet.