STUDY OF DUST IN THE VICINITY OF DIODE USING THE VOYAGER-1 PLASMA-WAVE INSTRUMENT

The flyby of Voyager 1 at Saturn yielded the detection of a large vari ety of plasma waves, for example, chorus, hiss, and electron cyclotron harmonics. Just before the outbound equator crossing, the Voyager 1 p lasma wave instrument detected a strong, well-defined low-frequency en hancement in signal levels. Initially, it was thought that this enhanc ement was due to plasma waves, but more recently it was suggested that dust impacts might be at least partial contributors. In this report w e present evidence that dust impacts are partly responsible for the lo w-frequency enhancement. A new method of analysis which relies mainly on the 16-channel spectrum analyzer has been used to derive the dust i mpact rate. The available wideband waveform observations (which have b een used previously to study dust impacts) were useful for calibrating the impact rate from the spectrum analyzer data. The mass and hence s ize of the dust particles were also obtained by analyzing the response of the plasma wave spectrum analyzer. The results show that the regio n sampled by Voyager 1 is populated by dust particles that have rms ma sses of up to few times 10(-11) and sizes of up to a few microns. The dust particle number density is of the order of 10(-3) m(-3). The opti cal depth of the region sampled by the spacecraft is approximately 10( -6). The particle population is centered at 2470(+/-150) km south of t he equatorial plane and has a north-south FWHM (full-width, half-maxim um) thickness of 4130(+/-450) km. The dust may be part of the E ring o r a localized ringlet associated with Dione.