ION-CYCLOTRON WAVES AT JUPITER - POSSIBILITY OF DETECTION BY ULYSSES

We evaluate the convective growth of ion-cyclotron waves in the Io pla sma torus using realistic plasma parameters. Significant wave amplific ation is restricted to two dominant frequency bands. As originally pro posed by Thorne and Moses [1983, 1985], waves between the O+ and H+ gy ro-frequencies may be excited at higher latitudes (lambda > 15-degrees ) in the region where H+ becomes the dominant ion. Strong cyclotron re sonant damping should prevent wave propagation to lower latitude. Even under optimum conditions the path integrated gain of such waves is mo dest and extremely sensitive to the properties of both the thermal pla sma and the cyclotron resonant energetic ions. Consequently, these wav es should be confined to a limited region of the torus (6 < L < 9). Th e equatorial region of the torus can be unstable to L-mode waves below the O+ gyro-frequency. Rapid amplification should drive waves to non linear amplitudes for any reasonable choice of the plasma properties. While the orbit of Ulysses passes through the Io torus close to the op timum location (near L = 8) to detect both the high frequency (10Hz) w aves at lambda > 15-degrees and the low frequency waves (< 0.5Hz) near the equator, the sensitivity of the magnetometer and the lower freque ncy threshold of the plasma wave detector offer only a marginal possib ility to clearly identify either of these important waves.