A pincer-shaped plasma sheet at Uranus
- Univ. of California, Los Angeles (USA)
A model from Voigt et al. (1987) and an MHD simulation from Walker et al. (1989) both show that the curvature of the plasma sheet at Uranus changes as the dipole tilt varies between 38{degree} and 22{degree}. The models suggest that one of the two partial traversals of the uranian plasma sheet made during the outbound trajectory of Voyager 2 can be explained as an entry into the highly curved plasma sheet that develops when Uranus is near the maximum dipole tilt value of 38{degree}; previously both partial traversals have been explained as anomalous. The spacecraft would have reversed its motion relative to the plasma sheet as the continued rotation diminished the dipole tilt and the retreating plasma sheet uncurled. As the dipole tilt approached its minimum value, spacecraft motion towards the neutral sheet resumed and the traversal of the plasma sheet was completed. Evidence from the PWS plasma wave detector suggests that the spacecraft trajectory skimmed the plasma sheet boundary layer for several hours prior to the partial immersion. The plasma sheet of the Voigt et al. model was not located near the spacecraft during this time interval. On the other hand, the MHD simulation reveals a plasma sheet that is more curved than in the Boigt et al. model; near maximum dipole tilt, the plasma sheet is pincer-shaped. The unusual geometry implies that Voyager 2 remained near the plasma sheet boundary layer during the period suggested by the PWS data. Thus the simulation accounts easily for the first of the plasma sheet encounters previously called anomalous. The second partial immersion remains anomalous, having previously been related to substorm activity, and thus is not discussed here. The stagnation distances of the earth and Uranus at the nose of the magnetopause were used to scale the Walker et al. (1989) simulation of the terrestrial magnetosphere to represent the uranian magnetosphere.
- OSTI ID:
- 5384282
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 95:A9; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
Similar Records
The orbits of the uranian satellites and rings, the gravity field of the uranian system, and the orientation of the pole of Uranus
Magnetic fields at Neptune
Related Subjects
GENERAL PHYSICS
URANUS PLANET
PLANETARY MAGNETOSPHERES
BOUNDARY LAYERS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICAL MODELS
MORPHOLOGY
ORIENTATION
PLASMA WAVES
ATMOSPHERES
EVALUATION
FLUID MECHANICS
HYDRODYNAMICS
LAYERS
MECHANICS
PLANETARY ATMOSPHERES
PLANETS
SIMULATION
640107* - Astrophysics & Cosmology- Planetary Phenomena