HR: 08:00h
AN: SH41C-01 INVITED     [Abstracts]
TI: Solar Wind Interaction With the Lunar Environment
AU: * Halekas, J S
EM: jazzman@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way, Berkeley, CA 94720 United States
AB: The Earth's Moon, lacking a substantial atmosphere or global magnetic field, presents one of the simpler obstacles to solar wind flow in our solar system. Despite this apparent simplicity, a rich array of interesting plasma physics occurs in the lunar environment. To first order, the Moon is completely unshielded from solar wind plasma and solar photons, and direct incidence of solar wind plasma can lead to implantation of volatiles and ion sputtering and pickup. The solar wind is blocked by the lunar obstacle, resulting in a plasma void on the night side. A potential drop across the wake boundary is generated as solar wind electrons attempt to refill the wake cavity, resulting in a tenuous high-temperature electron population and anisotropic ion beams in the wake. A system of diamagnetic currents is formed on the boundary surface, enhancing the magnetic field in the wake and reducing the field around it. Meanwhile, waves are generated by the unstable particle distributions generated by this interaction. On the day side, photon-driven positive charging of the lunar surface occurs. On the night side, on the other hand, charging is controlled by the tenuous wake plasma, and is generally electron-driven and negative. When the Moon traverses the Earth's magnetotail and is exposed to low-density plasma in the tail lobes and high-temperature plasma in the plasmasheet, extreme surface charging of up to hundreds of V positive and several keV negative can occur. Lunar surface charging may affect ion sputtering and likely results in significant dust transport. The presence of remanent crustal magnetism causes significant perturbations to this picture. Some crustal fields are large enough to stand off the solar wind (possibly affecting solar wind volatile implantation), and we observe large shock-like magnetic enhancements upstream from the largest crustal sources. The occurence of these "limb shocks" depends on solar wind parameters, suggesting that the crustal sources are only large enough and strong enough for solar wind plasma to react in a fluid-like way for certain upstream conditions.
DE: 5421 Interactions with particles and fields
DE: 5440 Magnetic fields and magnetism
DE: 6250 Moon (1221)
DE: 7815 Electrostatic structures
DE: 7851 Shock waves (4455)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005