Ulysses dust measurements near Jupiter

Solar wind implication on dust ion acoustic rogue waves

The relevance of the solar wind with the magnetosphere of Jupiter that contains positively charged dust grains is investigated. The perturbation/excitation caused by streaming ions and electron beams from the solar wind could form different nonlinear structures such as rogue waves, depending on the dominant role of the plasma parameters. Using the reductive perturbation method, the basic set of fluid equations is reduced to modified Korteweg-de Vries (KdV) and further modified (KdV) equation. Assuming that the frequency of the carrier wave is much smaller than the ion plasma frequency, these equations are transformed into nonlinear Schrödinger equations with appropriate coefficients. Rational solution of the nonlinear Schrödinger equation shows that rogue wave envelopes are supported by the present plasma model. It is found that the existence region of rogue waves depends on the dust-acoustic speed and the streaming temperatures for both the ions and electrons. The dependence of the maximum rogue wave envelope amplitude on the system parameters has been investigated.

Io as a source of the jovian dust streams

Streams of dust emerging from the direction of Jupiter were discovered in 1992 during the flyby of the Ulysses spacecraft, but their precise origin within the jovian system remained unclear. Further data collected by the Galileo spacecraft, which has been orbiting Jupiter since December 1995, identified the possible sources of dust as Jupiter's main ring, its gossamer ring, comet Shoemaker-Levy 9 (ref. 8) and Io. All but Jupiter's gossamer ring and Io have since been ruled out. Here we find that the dominant source of the jovian dust streams is Io, on the basis of periodicities in the dust impact signal. Io's volcanoes, rather than impact ejecta, are the dust sources.

Solar wind magnetic field bending of Jovian dust trajectories

From September 1991 to October 1992, the cosmic dust detector on the Ulysses spacecraft recorded 11 short bursts, or streams, of dust. These dust grains emanated from the jovian system, and their trajectories were strongly affected by solar wind magnetic field forces. Analyses of the on-board measurements of these fields, and of stream approach directions, show that stream-associated dust grain masses are of the order of 10(-18) gram and dust grain velocities exceed 200 kilometers per second. These masses and velocities are, respectively, about 10(3) times less massive and 5 to 10 times faster than earlier reported.