The Cassini radio and plasma wave investigation is designed to study radio emissions, plasma waves, thermal plasma, and dust in the vicinity of Saturn. Three nearly orthogonal electric field antennas are used to detect electric fields over a frequency range from 1 Hz to 16 MHz, and three orthogonal search coil magnetic antennas are used to detect magnetic fields over a frequency range from 1 Hz to 12 kHz. A Langmuir probe is used to measure the electron density and temperature. Signals from the electric and magnetic antennas are processed by five receiver systems: a high frequency receiver that covers the frequency range from 3.5 kHz to 16 MHz, a medium frequency receiver that covers the frequency range from 24 Hz to 12 kHz, a low frequency receiver that covers the frequency range from 1 Hz to 26 Hz, a five-channel waveform receiver that covers the frequency range from 1 Hz to 2.5 kHz in two bands, 1 Hz to 26 Hz and 3 Hz to 2.5 kHz, and a wideband receiver that has two frequency bands, 60 Hz to 10.5 kHz and 800 Hz to 75 kHz. In addition, a sounder transmitter can be used to stimulate plasma resonances over a frequency range from 3.6 kHz to 115.2 kHz. Fluxes of micron-sized dust particles can be counted and approximate masses of the dust particles can be determined using the same techniques as Voyager. Compared to Voyagers 1 and 2, which are the only spacecraft that have made radio and plasma wave measurements in the vicinity of Saturn, the Cassini radio and plasma wave instrument has several new capabilities. These include (1) greatly improved sensitivity and dynamic range, (2) the ability to perform direction-finding measurements of remotely generated radio emissions and wave normal measurements of plasma waves, (3) both active and passive measurements of plasma resonances in order to give precise measurements of the local electron density, and (4) Langmuir probe measurements of the local electron density and temperature. With these new capabilities, it will be possible to perform a broad range of studies of radio emissions, wave-particle interactions, thermal plasmas and dust in the vicinity of Saturn.

http://lasp.colorado.edu/~horanyi/graduate_seminar/Radio_Plasma_Wave.pdf

The Cassini Radio and Plasma Wave Investigation

Dusty plasmas are ubiquitous in low-temperature laboratory discharges as well as in the near-earth environment, planetary rings, and interstellar spaces. In this paper, updated knowledge of fundamentals of collective dust-plasma interactions and several novel phenomena are presented that have been observed in laboratories and in space dusty plasmas. Mechanisms that are responsible for the charging of dust grains are discussed, and the fact that the dust charge perturbation is a new dynamical variable in a dusty plasma. The underlying physics of different forces that act on a charged dust grain is reviewed. In dusty plasmas, there are new attractive forces (e.g., due to wakefield and ion focusing effects and dipole-dipole interactions between unevenly charged dust rods). Furthermore, in the presence of an ensemble of charged dust grains, there are collective dust-plasma interactions featuring new waves (e.g., the dust acoustic wave, the dust ion-acoustic wave, the dust lattice wave, etc.), new instabilities, and coherent nonlinear structures (dust acoustic and dust ion-acoustic shocks, dust voids, and dust vortices), which are also discussed. Theoretical models for numerous collective dust-plasma interactions are compared with existing observations from laboratories and space environments.

Colloquium : Fundamentals of dust-plasma interactions

We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 ± 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.

https://science.sciencemag.org/content/sci/307/5713/1255.full.pdf

Radio and plasma wave observations at Saturn from Cassini's approach and first orbit.

The Cassini-Huygens Cosmic Dust Analyzer (CDA) is intended to provide direct observations of dust grains with masses between 10-19 and 10-9 kg in interplanetary space and in the jovian and satumian systems, to investigate their physical, chemical and dynamical properties as functions of the distances to the Sun, to Jupiter and to Saturn and its satellites and rings, to study their interaction with the saturnian rings, satellites and magnetosphere. Chemical composition of interplanetary meteoroids will be compared with asteroidal and cometary dust, as well as with Saturn dust, ejecta from rings and satellites. Ring and satellites phenomena which might be effects of meteoroid impacts will be compared with the interplanetary dust environment. Electrical charges of particulate matter in the magnetosphere and its consequences will be studied, e.g. the effects of the ambient plasma and the magnetic field on the trajectories of dust particles as well as fragmentation of particles due to electrostatic disruption.

http://lasp.colorado.edu/~horanyi/graduate_seminar/Dust_Analyzer.pdf

The Cassini Cosmic Dust Analyzer

Spherical Kadomtsev-Petviashvili equation and nebulons for dust ion-acoustic waves with symbolic computation

Micron-sized particles detected near Saturn by the Voyager plasma wave instrument☆

Micron-size particles detected near Saturn by the Voyager plasma wave instrument

This paper presents observations of the parametric decay and spatial collapse of Langmuir waves driven by an electron beam streaming into the solar wind from the Jovian bow shock. High-resolution frequency-time spectrograms from Voyager 1 and 2 show that long wavelength Langmuir waves upstream of the bow shock are very effectively converted into short wavelength Langmuir waves which are no longer in resonance with the beam. This conversion is shown to be the results of a nonlinear interaction involving the beam-driven pump, a sideband emission and a low level of ion-acoustic turbulence which always appears to be present in the solar wind. The onset of the interaction occurs at about the time that the amplitude of the pump wave saturates, which indicates that parametric processes are probably playing an important role in stablizing the electron beam. Detailed examination of the electric field wave-forms shows the beam-driven Langmuir wave emission breaks up into a very complex sideband structure with both positive and negative Doppler shifts.Positive frequency shifts correspond to waves propagating away from the sun and negative frequency shifts correspond to waves propagating toward the sun. In some cases the sideband emissions consist of isolated wave packets with very short durations,more » sometimes lasting only a few msec. These short duration bursts, which are usually very intense, are thought to consist of envelope solitons which have collapsed down to spatial scales of only a few Debye lengths.« less

D. Gallagher

Papers

Micron-sized particles detected near Saturn by the Voyager plasma wave instrument☆

Micron-size particles detected near Saturn by the Voyager plasma wave instrument

Parametric interaction and spatial collapse of beam-driven Langmuir waves in the solar wind. [upstream of Jupiter bow shock