PLASMA OBSERVATIONS IN THE RING PLANE OF SATURN

We present the first detailed analysis of the Voyager 2 plasma science (PLS) observations in the vicinity of the ring plane of Saturn. We find three types of plasma in the region between z = 0.9 R(S) and z = -0.7 R(S), namely, a tenuous and isotropic plasma derived from the large icy satellites, a dense and anisotropic plasma, and an anomalously anisotropic plasma in the ring plane region itself. We interpret these results to confirm a previously published hypothesis, according to which the natural Kronian inner magnetosphere plasma is derived from two sources, a tenuous plasma from the large icy satellites and a dense plasma from the atmosphere of the main rings. The anomalously anisotropic plasma is interpreted as the result of impacts of G ring ice motes. The in situ plasma measurements, thus, provide an additional delineation of the poorly observed G ring.