Monday, January 25, 2010

Deflection and enhancement of solar energy particle flux at the Moon by structures within the terrestrial magnetosphere

Though no two encounters are the same, each orbit the Moon encounters Earth's relatively substantial magnetotail, as seen in the greatly simplified NASA schematic above. The force of solar wind and the interplanetary magnetic field vary most, as with similar encounters with Earth's shadow the Moon's slice of the larger magnetotail takes it through differing depths and layers. Varying least are the poles and intensity at a distance of Earth's dynamo. The modifying effects of such encounters on the Moon's own dynamic processes, particularly upon the production of water and hydroxyl and the charging and levitation of submicron-sized lunar dust have a direct impact on future human activity there.

E. M. Harnett
Department of Earth and Space Sciences
University of Washington, Seattle

The Moon spends 25% of its orbit within the terrestrial magnetosphere. Particle tracking is used to investigate access points of 35 MeV and 760 MeV particles into the magnetosphere for both quiet and disturbed magnetospheric conditions. The results indicate that solar energetic particle (SEP) flux at the Moon can be reduced for storm conditions when the magnitude of the magnetic field in the sheath is enhanced, as particles in the 35 MeV range have limited access to the magnetosphere for storm conditions. Plasmoids are also effective at reducing SEP flux from the tailward direction. The results also indicate that the flux of SEPs from the dawnside of the magnetosphere can be focused into the current sheet, leading to a potential enhancement in SEP flux at the Moon. Particles traveling up the tail for both quiet and storm conditions tended to experience the greatest deflection away from the central tail.

The full paper is available
by subscription to the
Journal of Geophysical Research,

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