Transverse Waves in the Inner Saturn Magnetosphere

The Cassini magnetic field investigation detected two very different types of transverse fluctuations during the Saturn Orbit Insertion pass, in the frequency range that is resonant with heavy ions. Neither wave has an analogue in the Galileo measurements at Jupiter. The first wave phenomenon was seen inbound about 6 Rs planetocentric, surrounding a significant diamagnetic depression of unknown origin. The waves were almost purely transverse with little compressional component but they were also linearly polarized and not circularly polarized as expected for ion resonance. A second period of transverse waves appeared outbound from about 4.26 Rs to 5.27 Rs 5 hours after the orbit insertion burn. These waves were close to the local gyro frequency for ions with mass to charge ratios from that of singly ionized water to singly ionized carbon dioxide. These waves were left-hand elliptically polarized, propagating at a finite angle to the magnetic field with a smaller but significant compressional component. The mass range of these ions coincide with the expected major components of the exhaust of Cassini's injection engine. Thus these observations appear to be the first detection of the artificial production of waves in a magnetosphere other than that of the Earth. Observations during Cassini's second orbit will also be discussed.