THE EFFECTS OF ELECTROSTATIC FORCES AND RANDOM VELOCITIES ON DUST RING THICKNESS PROFILES IN RINGS WITH A DUST SIZE DISTRIBUTION

We have considered vertical density profiles of dust rings with a dust size distribution. The density profiles are determined by random vertical velocities of the dust, the vertical component of gravity, and the electrostatic lifting force on the charged dust due to the self-screening electric field of the dust ring. We reconsider the case of electrostatically supported dust rings with monosized dust and no random vertical velocity (Havnes and Morfill, 1984). We thereafter look at a pure electrostatically supported dust ring with dust size distribution, which we find will be perfectly separated according to dust size with the largest dust particles in the ring plane and the smallest and lightest furthest above the plane. When the dust particles are given a random velocity, this leads to an increasing mixing of the different dust sizes as the random velocity is increased. The electrostatic effect will still lead to separation of dust particles according to size, and we find that a general trend in dust rings will be the existence of a halo of small dust particles with a degree of mixing of dust sizes near the ring plane which is dependent on the dust random kinetic energy and on the dust and plasma parameters.