Survey of low‐energy plasma electrons in Saturn's magnetosphere: Voyagers 1 and 2

Abstract

For reference purposes we have superimposed dipole field lines in Figure 1b. There are corrections to Saturn's dipole field, as evolving model calculations by Connerney et al. (1981, 1Sa82) suggest the presence of quadrupole and octupole terms in the internal field and a ring current between Lx8.5 and 15.5; these corrections become important outside L=8, where the ring current produces an inflation of the dipole field lines.The lack of tilt in most magnetic field models makes the spin equator nearly congruent with the magnetic equator. This has the unfortunate consequence that each spacecraft does not make as many crossings of Saturn's plasma sheet during an enc;.Lmter as was the case during the Jupiter encounters. This symmetry, however, produces a simplification in our interpretation of the plasma data, as it makes the centrifugal and magnetic equatorial planes nearly coincident. Under this condition, the plasma, regardless of its thermal characteristics, will have mirror symmetry about the equatorial plane. As noted in Smith et al. (1980), the corotational electric field can dominate the convective electric field due to the solar wind out to radial distances in excess of 21 R S , the average radial position of the noon time magnetopause boundary. In first approximation, one expects Saturn's magnetosphere to be azimuthally symmetric inside L05; the magnetic field data reported by Smith et al. (1980) and Ness et al. ( , 1982 support this expectation. Finally, using the above approximations of dipole field, mirror symmetry, azimuthal symmetry, and making the additional assumption of "steady-state" one can increase the coverage of the spatial distribution of the plasma in L, Z space by combining the plasma data from all three encounters. In this way, Bridge et al. (1982) were able to construct a fairly extensive description of the plasma morphology.

Saturn's polar ionospheric flows and their relation to the main auroral oval

“…We may then estimate N ≈0.2 cm −3 (some fraction of the dayside magnetosheath density) and W th ≈50 eV (for plasma heated at the magnetopause) (e.g. Sittler et al, 1983). We then find that the limiting current given by Eq.…”

Modulation of ion-acoustic waves in a nonextensive plasma with two-temperature electrons

“…The observations of the voyager PLS [18,19] have also shown the existence of both cool and hot electrons populations (non-Maxwellian) in Saturn's Magnetosphere. One of such distributions as reported by Renyi [20] and proposed by Tsallis [21] is the Boltzmann-Gibbs-Shannon (BGS) entropy in which the degree of nonextensivity of the plasma particles is characterized by the entropic index q, i.e., the distribution function with q < 1, compared with the Maxwellian one (q = 1) indicates the system with more superthermal particles (superextensivity), whereas the q distribution with q > 1 is suitable for plasmas containing a large number low-speed particles (subextensivity).…”

A model of the plasma flow and current in Saturn's polar ionosphere under conditions of strong Dungey cycle driving

“…These boundary currents may be carried partially in some lower latitude portion by hot electrons from the outer magnetosphere, with a number density of ∼0.01 cm −3 and a thermal energy of ∼1 keV according to Voyager measurements (Richardson, 1986(Richardson, , 1995, and partially in some higher-latitude portion by magnetosheath (cusp) electrons with a number density of ∼0.2 cm −3 and a thermal energy of ∼50 eV (Sittler et al, 1983). The outer magnetospheric source has a limiting current from Eq.…”