A SURVEY OF LOW-FREQUENCY WAVES AT JUPITER - THE ULYSSES ENCOUNTER

We report the results of a survey of low-frequency (LF) plasma waves d etected during the Ulysses Jupiter flyby. In the Jovian foreshock, two predominant wave periods are detected: 10(2)-s and 5-s, as measured i n the spacecraft frame. The 10(2)-s waves are highly nonlinear propaga te at large angles to B(o) over arrow pointing right (typically 50-deg rees), are steepened, and sometimes have attached whistler packets. Fo r the interval analyzed the 10(2)-s waves had mixed right-and left-han d polarizations. We argue that these are all consistent with being rig ht-hand magnetosonic waves in the solar wind frame. The 10(2)-s waves with attached whistlers are similar to cometary waves. The trailing po rtions are linearly polarized and the whistler portions circularly pol arized with amplitudes decreasing linearly with time. The emissions ar e generated by approximately 2-keV protons flowing from the Jovian bow shock/magnetosheath into the upstream region. The inability is the io n beam instability. Higher Z ions were considered as a source of the w aves but have been ruled out because of the low sunward velocities nee ded for their resonance. The 5-s waves have DELTAB over arrow pointing right/ B(o) almost-equal-to 0.5, are compressive and are left-hand po larized in the spacecraft frame. Local generation by three different r esonant interactions were considered and have been ruled out. One poss ibility is that these waves are whistler mode by-products of the steep ened lower-frequency magnetosonic waves. Mirror mode structures were d etected throughout the outbound magnetosheath passes. For these struct ures, the theta(kB) values were consistently in the range of 80-degree s to 90-degrees, exceptionally high values. Assuming 1-keV protons, th e spacing between the magnetic decreases is approximately 10-20 r(p). Close to the magnetopause, small amplitudes (DELTAB over arrow pointin g right/B(o) almost-equal-to 0.15), transverse waves were detected. Wi thin the wave packet, right, left- and linear polarizations were found . These may be similar to waves detected in the Earth's plasma depleti on layer. Within the Jovian low-latitude boundary layer, enhanced tran sverse spectral power was detected at frequencies just below the proto n cyclotron frequency. A total magnetic power of 10(-1) nT2 was determ ined. Cross-field diffusion of approximately 1-keV protons yields a ca lculated boundary layer thickness of 0.15 R(J). This is in excellent a greement with previous measurements. Transverse left-hand (spacecraft frame) waves were detected within the Jovian magnetosphere. These wave s have periods of 5-8 min, are elliptically to circularly polarized an d propagate in a range of 10-degrees to 43-degrees relative to B(o) ov er arrow pointing right. It is most likely that these waves are genera ted by an ion beam instability. Assuming S+, we get a resonant paralle l energy of 60 keV.