DRIFT MECHANISM CAUSED BY A NONLINEAR-WAVE AND THE CASSINI DIVISION AND URANIAN RINGS FORMATION

The mechanism leading to the observed coexistence of gaps and narrow r inglets in the planetary rings is found. It is based upon the quasi-st ationary radial drift of the matter under action of two forces in the disk plane: the Coriolis force and the Reynolds stresses. To an accura cy of the factor of 2 the first force coincides with the Lorentz force , therefore the radial drift in rings is similar to the gradient drift of plasma in the magnetic field. The second force is produced by the wave generated by the nearby satellite in the resonance position. In i nertial systems, the second force alone causes a matter flow in its di rection, called acoustic streaming. Since the radial drift is caused b y nonlinear time-averaged force of high-frequency harmonic interaction s in the wave, it exists in the wave propagation zone: from the birth place of the wave-the resonance position, up to the reflection point o f the wave, where its group velocity vanishes, Our estimations show th at the size of the density wave propagation zone corresponding to the density wave which had been formerly generated the 2:1 orbital resonan ce with Mimas is consistent with the width of the Cassini Division. In our case the nature of the radial drift is such that first of all it clears out the farthest from the resonance position; later, the closer areas also get affected by the drift. The zone closest to the resonan ce position itself is the last to be involved in the process. The matt er carried away by the drift is partially accumulated near the resonan ce position forming a narrow dense ringlet. (C) 1996 American Institut e of Physics.