MICRON-SIZED PARTICLES DETECTED IN THE VICINITY OF JUPITER BY THE VOYAGER PLASMA-WAVE INSTRUMENTS

Wideband waveform data obtained by the plasma wave instruments onboard the Voyager 1 and 2 spacecraft have been used to study micron-sized d ust particles in the vicinity of Jupiter. The technique used was devel oped during the flybys of Saturn, Uranus, and Neptune, and makes use o f the fact that a particle striking the spacecraft at 10-20 km/s cause s a voltage pulse in the plasma wave receiver. The waveform of the vol tage pulse is much different than the waveform of plasma waves and pro vides a highly reliable method of detecting micron-sized dust particle s. Although the dust impact rate observed in the vicinity of Jupiter i s much lower than the rates at Saturn, Uranus, and Neptune, the partic les are easily detectable. Approximately 1200 48-second frames of wide band waveform data were examined in the vicinity of Jupiter. Dust impa ct signatures were found in approximately 20% of these frames. The pea k impact rates are about 1 impact per second, and the peak number dens ities are about 10(-5) m(-3). Most of the impacts occurred near the eq uatorial plane at radial distances less than about 35 R(J) from Jupite r. Analysis of the detection threshold indicates that the particles ha ve masses greater than 10(-11) g, which corresponds to particles with diameters of a few micrometers or larger.