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Astron. Astrophys. 346, 1011-1019 (1999)

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Dynamics of particles in Saturn's E ring: effects of charge variations and the plasma drag force

Valery V. Dikarev

Astronomical Institute, St. Petersburg University, Stary Peterhof, 198904 St. Petersburg, Russia (valery@astro.spbu.ru)

Received 20 November 1998 / Accepted 30 March 1999

Abstract

Dynamics of the E ring dust grains in Saturn's magnetosphere are investigated. Apart from the solar radiation pressure and the planetary oblateness, the Lorentz force due to variable charge and the plasma drag are taken into account.

The Lorentz force is considered for the grain's charge which does not depend on time explicitly but is a function of the grain's distance from the planet. Under this assumption and neglecting small orbital inclinations the Lorentz force leaves the eccentricity unaltered but causes precession or regression of the orbit with the rate determined by the charging model. It is shown that the orbital evolution of the grains having a variable charge does not differ qualitatively from that of the grains with a constant charge.

The action of the plasma drag is investigated analytically in the approximation of small eccentricities and zero inclinations. The direct drag due to the fraction of the heavy ions ([FORMULA], [FORMULA]) is found to be the main drag force in the inner magnetosphere of Saturn. The plasma drag alone changes the semimajor axis. The rate of the semimajor axis growth due to the plasma drag is large enough to allow the submicron-sized grains ejected from Enceladus to survive against recollision with the parent satellite. When combined with the radiation pressure, the plasma drag also introduces the trend in the oscillating eccentricity which leads to the growth of the eccentricity of the E ring grain orbits.

Key words: methods: analytical – celestial mechanics, stellar dynamics – meteors, meteoroids – planets and satellites: general – planets and satellites: individual: Enceladus

Send offprint requests to: V.V. Dikarev

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© European Southern Observatory (ESO) 1999

Online publication: June 17, 1999
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