# Gravitoelectrodynamics

### From (The Plasma Universe Wikipedia-like Encyclopedia)

*See also: Dusty plasmas: dynamics*

**Gravito-electrodynamics** is the physics of the influence of gravity and electromagnetic forces on particle. The motion of solid particles in a plasma follows the *momentum equation* for ions and electrons:

where m, q are the mass and charge of the particle, **g** is the gravitation acceleration, m*v*_{c}**v** is due to viscosity, and **f** respresents all other forces including radiation pressure. *q* (**E** + **v** x **B**) is the Lorentz force, where **E** is the electric field, **v** is the velocity and **B** is the magnetic field.

Then depending in the size of the particle, there are four categories:

**Very small particles**, where q (**E**+**v**×**B**) dominates over m**g**.**Small grains**, where q/m ≈ √G, and plasma still plays a major role in the dynamics.**Large grains**, where the electromagnetic term is negligible, and the particles are referred to as grains. Their motion is determined by gravity and viscosity, and the equation of motion becomes m*v*_{c}**v**= m**g**.**Large solid bodies**. In centimeter and meter-sized bodies, viscosity may cause significant perturbations that can change an orbit. In kilometer-sized (or more) bodies, gravity and inertia dominate the motion.

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## References

- Kikuchi, Hiroshi,
*Electrohydrodynamics in dusty and dirty plasmas: gravito- electrodynamics and EHD*(2001) Publ. Kluwer Academic Publishers, 2001, xx, 207 p. Astrophysics and space science library (ASSL), Vol. 258. ISBN 0792368223 - Mendis, D. A.; Houpis, H. L. F.; Hill, J. R., "The gravito-electrodynamics of charged dust in planetary magnetospheres" (1982)
*Journal of Geophysical Research*, vol. 87, May 1, 1982, p. 3449-3455 - Mendis, D. A. "Gravito-electrodynamics and the structure of planetary ring systems" (1984)
*Indian Academy of Sciences, Proceedings*(Earth and Planetary Sciences) (ISSN 0370-0089), vol. 93, Aug. 1984, p. 177-188. - Mendis, D. A.; Hill, J. R.; Houpis, H. L. F., "Charged dust in Saturn's magnetosphere" (1983) In: Lunar and Planetary Science Conference, 13th, Houston, TX, March 15-19, 1982, Proceedings. Part 2. (A83-21281 07-91) (Full text online)