A survey of the plasma environment within Jupiter's bow shock is presented in terms of the in situ, calibrated electron plasma measurementa made between 10 eV and 5. c .5 keV by the Voyager Plasma Science Experiment (PLS). These measurements have been analyzed and corrected for spacecraft potential variations; the :'.ata have been reduced to nearly model independent macroscopic parameters of the local electron density and temperature. The electron parameters are derived without reference to or internal calibration from the positive ion measurements made by the PL$ experiment. Extensive statistical and direct comparisons with other determinations of the local plasma charge density clearly indicate that the analysis procedures used have successfully and routinely discriminated between spacecraft sheath and ambient plasmas. These statistical cross correlations have been performed over the density range of 10-3 to 2 x 10 2 /cc. These data clearly define the bow shock, the magnetosheath (30-50 eV) the magnetosphere (10 -2 /cc, 2-3 keV) as well as the periodic appearances of the plasma sheet which are illustrated to be routinely cooler than the surroundings. The proximity of the plasma sheet define:. a regime in the magnetosphere where very cold electron plasma (as low as 50 eV) at 40 R can be seen in unexpected density enhancements. These plasma "spikes" in the density can often represent an order of magnitude enhancement above the ambient density and are correlated with diamagnetic depressions. These features have been seen at nearly all magnetic latitudes within the plasma sheet. The temperature within these spikes is lowered by similar factors indicating that the principal density enhancements are of cold plasma. The plasma sheet when traversed in the outer magnetosphere has a similar density and temperature morphology as that seen in these 11 3pikes". In all oases the plaama sheet crossing lasts for intervals commensurate with that defined by the diamagnetic depression in the simultaneously measured and uisplayed magnetic field. The electron temperatures in the plasma sheet in the outer and middle magnetosphore appear to have a positive radial gradient with jovicentric distance. The electron temperature is observed to be lower on the centrifugal, side of the minimum magnetic field strength seen in each sheet, while the suprathermal, electron density is enhanced symmetrically about the locally indicated magnetic equator. The electron distribution functions within the plasma sheet are markedly non-Maxwellian; during the density enhancemeW s of the plasma sheet tie thermal sub-population is generally enhanced more than the suprathermal population. The suprathermal fraction of the electron densf..y within the plasma sheet is an increasing function of jovicentric distance.Direct, in situ sampling of the electron plasma environment of lo's torus clearly illustrates that the system is demonstrably removed from local, thermodynamic equilibrium; these measurements illustrate that between 5.5 and 8.9 R, there are s...

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We consider the positive ion data gathered by the Voyager Plasma Science experiment in the middle magnetosphere of Jupiter. The experiment measures positive ions with energies per charge between 10 and 5950 V. The observations are analyzed to obtain the mass and charge densities, velocity components, and temperatures of the low‐energy plasma population. The reduced data set is discussed in the context of the outstanding questions concerning this plasma population and its dynamics. We find that on the dayside, there exists a transonic to highly supersonic positive ion population which tends to move azimuthally but does not rigidly corotate with the planet. These ions provide the inertia of the magnetospheric plasma inside of ∼40 RJ. The mass density is everywhere dominated by heavy ions, and the mass density gradient is consistent with outward diffusion from the Io plasma torus via flux tube interchange. The ions tend to be concentrated in a plasma sheet which is associated with the current sheet inferred from the magnetic field observations. The plasma in the sheet is relatively cool (∼20 eV) in comparison with plasma at higher magnetic latitudes (≳100 eV). In addition to the azimuthal flow pattern, we find a local time asymmetry in the data which we interpret as flow away from the current sheet on the dayside and toward the current sheet on the nightside. This dynamic expansion and contraction of the plasma sheet is presumably driven by the asymmetry in the magnetosphere due to the solar wind interaction.

Measurements below 6 keV from the plasma science experiment on the Voyager spacecraft show that positive ions with temperatures as low as 30 eV to several keV are observed to distances at least as great as 40 RJ in the dayside Jovian magnetosphere. When velocity determinations are possible between ∼ 10 RJ and ∼40 RJ, the plasma velocity component along the rigid corotation direction is found to be consistently less than the full corotation speed. Positive ion measurements above ∼28 keV from the low energy charged particle experiment on Voyager demonstrate the existence of positive ions with temperatures of 20‐30 keV at all distances greater than 30 RJ. Taken together, these observations suggest that the low energy plasma population from ∼30 RJ to at least 40 RJ frequently contains both a cold and a hot component. A two‐component plasma of this nature may indicate different sources, acceleration mechanisms, or time histories for the disparate components. It may also be indicative of a single acceleration mechanism which is highly energy dependent.

Extensive measurements of low-energy plasma electrons and positive ions were made during the Voyager 1 encounter with Saturn and its satellites. The magnetospheric plasma contains light and heavy ions, probably hydrogen and nitrogen or oxygen; at radial distances between 15 and 7 Saturn-radii (Rs) on the inbound trajectory, the plasma appears to corotate with a velocity within 20 percent of that expected for rigid corotation. The general morphology of Saturn's magnetosphere is well represented by a plasma sheet that extends from at least 5 to 17 Rs, is symmetrical with respect to Saturn's equatorial plane and rotation axis, and appears to be well ordered by the magnetic shell parameter L (which represents the equatorial distance of a magnetic field line measured in units of Rs). Within this general configuration, two distinct structures can be identified: a central plasma sheet observed from L = 5 to L = 8 in which the density decreases rapidly away from the equatorial plane, and a more extended structure from L = 7 to beyond 18 Rs in which the density profile is nearly flat for a distance +/- 1.8 Rs off the plane and falls rapidly thereafter. The encounter with Titan took place inside the magnetosphere. The data show a clear signature characteristic of the interaction between a subsonic corotating magnetospheric plasma and the atmospheric or ionospheric exosphere of Titan. Titan appears to be a significant source of ions for the outer magnetosphere. The locations of bow shock crossings observed inbound and outbound indicate that the shape of the Saturnian magnetosphere is similar to that of Earth and that the position of the stagnation point scales approximately as the inverse one-sixth power of the ram pressure.