Plasma pressure in the environment of Jupiter, inferred from voyager 1 magnetometer observations
- NASA Goddard Space Flight Center, Greenbelt, MD (USA)
A spherical harmonic model of Jupiter's planetary magnetic field is combined with a self-consistent model of the Jovian magnetodisc. Assuming that the pressure P in the middle (and outer) magnetosphere is related to the unit flux tube volume V through PV{sup {gamma}} = const, the fit yields a value of 0.88 for {gamma}. If the hot (30 keV) plasma is transported adiabatically inward under the interchange instability triggered by the centrifugal force of the heavy torus ions, losses are not sufficient to account for such a low value of {gamma} beyond L = 10. Closer to the planet, as the outer edge of the Io plasma torus is approached (at distances between 7 and 9 R{sub j} from Jupiter), PV{sup {gamma}} is found to decrease inward, as expected from the particle measurements, which identified an inner boundary of the particle fluxes in that region. At the magnetic equator, the pressure estimates were compared with the ones obtained from direct particle measurements (low-energy charged particle (LECP) experiment). Assuming a mixture of O{sup +} and H{sup +} at the same temperature (or with the same power law exponent), consistency between those two independent determinations of the pressure would require that the pressure produced by H{sup +} constitute 18-36% (at most) of the total pressure, at distances between 13 and 21 R{sub J}. Finally, as concerns the internal field coefficients, despite an overall consistency, a slight variability is found between the present estimates and previous ones derived from the same data set, which puts some limitations on the accuracy with which internal coefficients can be determined from the Voyager 1 encounter alone.
- OSTI ID:
- 5833695
- Journal Information:
- Journal of Geophysical Research; (USA), Vol. 94:A11; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
JUPITER PLANET
PLANETARY MAGNETOSPHERES
PLASMA PRESSURE
ADIABATIC PROCESSES
COMPARATIVE EVALUATIONS
ENVIRONMENT
IONIC COMPOSITION
MAGNETIC FIELDS
MATHEMATICAL MODELS
PIONEER SPACE PROBES
PLASMA DRIFT
SPHERICAL HARMONICS
VARIATIONS
ATMOSPHERES
PLANETARY ATMOSPHERES
PLANETS
SPACE VEHICLES
VEHICLES
640107* - Astrophysics & Cosmology- Planetary Phenomena