Transport of Dust in Near-Surface Plasma Sheaths

Details Transport of Dust in Near-Surface Plasma Sheaths Transport of Dust in Near-Surface Plasma Sheaths

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja....13635c&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #13635

Physics

Scientific paper

A plasma sheath develops at the surface of asteroids and airless planetary satellites due to collection of solar wind ions and electrons. Dust particles in the regolith are charged from solar wind and photoelectron currents and can be levitated, transported, and lost from the surface due to the electric field in the sheath. A similar phenomenon can occur on the dayside with the production of a photoelectron sheath due to photoemission from the surface induced by the solar UV flux. We have performed experiments in which dust is stably levitated in a plasma sheath. These experiments also show net transport of dust in the sheath due to interparticle forces. Numerical simulations of charged dust in a photoelectron sheath also show that net horizontal transport can occur. In these simulations individual particle charges and trajectories are integrated over the course of a day on an asteroid surface segment with imposed topography. Shadowing results in inhomogeneities in the photoelectron sheath. This leads to net deposition of levitated dust in shadowed areas and provides a possible explanation for the smooth deposits observed in the floors of craters on the asteroid Eros. In a 2-D simulation of a crater on Eros we find that dust particles lifted off the surface and transported in a photoelectron sheath are preferentially deposited in a model crater. For an asteroid the size of Eros with a surface potential of -200V, dust particles lifted off the surface are not accelerated to escape velocity (~10 m/s) by the plasma sheath, but particles as large as 40 micrometers in diameter may be levitated. In contrast, over objects with significantly larger surface accelerations, such as the Moon, the largest particle that can be levitated is only 2 micrometers in diameter. We will present the results of our experiments and numerical simulations on dust levitation and transport from planetary surfaces, including conditions that lead to loss of dust from the object and modification of the surface distribution of fine grains in the regolith.

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