Electron signatures of satellite sweeping in the magnetosphere of Uranus

Journal Article · Wed May 01 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA02629· OSTI ID:5225178

Cooper, J F; Stone, E C ^[1]

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1. California Inst. of Tech., Pasadena (USA)

The Voyager 2 Cosmic Ray System found large-scale macrosignatures of satellite sweeping for MeV electrons near the orbits of the satellites Miranda, Ariel, and Umbriel in the magnetosphere of Uranus. Due to the large magnetic inclinations of satellite orbits at Uranus, sweeping rates vary along the orbits with the McIlwain L parameter. However, no evidence was found, where expected, for fresh sweeping signatures at such positions. Although the maximal electron intensity occurs near Voyager 2's minimum L (4.67) as predicted by the Q{sub 3} field model, the intensity minima in the macrosignatures show large outward displacements ({le}0.5 R{sub U}) from minimum-L positions of the associated satellites. These radial displacements increased with measured electron energy and at higher magnetic latitudes. Pitch angle distributions are generally more anisotropic outside the macrosignatures and more isotropic within, as determined from comparison of inbound and outbound intensity profiles at different latitudes. These anisotropy measurements provide the basis for latitudinal flux extrapolation, which when coupled with power law scaling of spectral distributions allow the calculation of phase space density profiles. The latter show local minima in the macrosignatures and are indicative of distributed electron sources in the inner magnetosphere and/or nonadiabatic transport processes such as pitch angle scattering and magnetospheric recirculation. Preliminary diffusion coefficients with values D{sub LL} {approximately} 10{sup {minus}7}-10{sup {minus}6} R{sub S}{sup 2} and radial dependence D{sub LL} {approximately} L{sup 3}-L{sup 4} have been estimated for the macrosignatures. The low-order L dependence of D{sub LL} is consistent with diffusion driven by ionospheric dynamo. However, modeling of radial and pitch angle diffusion is required to assess the formative processes for the macrosignatures before more physically meaningful transport parameters can be determined.

• OSTI ID: 5225178
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A5; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
URANUS PLANET
PLANETARY MAGNETOSPHERES
ANGULAR DISTRIBUTION
ANISOTROPY
CHARGED-PARTICLE TRANSPORT
COMPARATIVE EVALUATIONS
DIFFUSION
ELECTRONS
MATHEMATICAL MODELS
MORPHOLOGY
SATELLITES
SCATTERING
TRAPPED ELECTRONS
VOYAGER SPACE PROBES
ATMOSPHERES
DISTRIBUTION
ELEMENTARY PARTICLES
EVALUATION
FERMIONS
LEPTONS
PLANETARY ATMOSPHERES
PLANETS
RADIATION TRANSPORT
SPACE VEHICLES
VEHICLES
640107* - Astrophysics & Cosmology- Planetary Phenomena