Radio emission signature of Saturn immersions in Jupiter's magnetic tail

During the interval from about May through August 1981, when Voyager 2 was inbound to Saturn, the planetary radio astronomy instrument measured repeated, dramatic decreases in the intensity of the Saturn kilometric radiation (SKR). The emission dropouts averaged two orders of magnitude below mean energy levels and varied from about 1 to 10 Saturn rotations in duration. Comparison with pre‐Saturn encounter Voyager 1 observations (June to November 1980) shows that the SKR dropouts were unique to the Voyager 2 observing interval, consistent with the closer proximity of Saturn to Jupiter's distant magnetotail in 1981. Further, the dropouts occurred on the average at times when Voyager 2 is known to have been within or near Jupiter's magnetic tail. Interpretation of these events as the radio signatures of successive Saturn immersions into Jupiter's tail or wake region is consistent with the independent evidence that the SKR radio source is driven externally by the solar wind ram pressure. The dropouts are identical to the one observed just after Voyager 2 closest approach to Saturn, providing the best evidence that Saturn was within Jupiter's tail at the time of the encounter. The sequence of events during this Saturn tail encounter is deduced.