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C. J. Mitchell, M. Horanyi, J. E. Howard (Laboratory for Atmospheric and Space Physics)
A population of dust grains moving in a retrograde sense about Jupiter have been observed by the Galileo spacecraft. This dust is believed to be captured from the interplanetary medium through interactions with the planetary magnetosphere.
Here we use computer simulations to investigate this process at Saturn. We restrict ourselves to equatorial orbits by assuming the magnetic field is a dipole aligned with the planetary rotation axis, a good approximation for Saturn. The dust grains are launched towards the planet with an initial velocity equal to the escape velocity, and with various impact parameters. The dust grains charge to an equilibrium voltage which increases linearly with radius inside the magnetosphere but is constant outside. The charging time is inversely proportional to the grain radius.
A prevalence of retrogade captures is observerd, with the number of captures depending on the grain radius. An exact constant of the motion is used to determine the final positions of the grains and to explain the observed tendency for the prevalence of retrograde captures.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.