Modeling the Interaction Between the Moon and the Solar Wind
Mats Holmström
Swedish Institute of Space Physics
What is the general morphology of the solar wind flow around the Moon?
Traditionally, bodies that lack a significant atmosphere and internal magnetic fields, such as the Moon, have been considered passive obstacles to the solar wind. The solar wind ions and electrons directly impact the surface of the Moon due to the lack of atmosphere, and the interplanetary magnetic field passes through the obstacle relatively undisturbed. Since the solar wind is absorbed by the bodies, a wake is created behind the object. This wake is gradually filled by solar wind plasma downstream of the body, through thermal expansion and the resulting ambipolar electric field, along the magnetic field lines.
However, recent measurements at the Moon by the Kaguya (Selene) mission and by the SARA instrument on-board Chandrayaan-1 suggest that the Moon?s plasma environment is more complicated than previously thought. The observations show that 0.1-1% of the solar wind protons are reflected by the surface of the Moon, with velocities that are a significant fraction of the solar wind velocity. These reflected protons will affect the global Moon?solar wind interaction, and could also explain earlier observations by Apollo and Nozomi.
Here we investigate the global Moon?solar wind interaction using a hybrid model (particle ions, fluid electrons), and focus in particular on the effects of reflected solar wind protons. We also try to identify what processes can be represented well by a hybrid model. The model results are compared to available observations of magnetic fields and ion fluxes.
Created 2010-09-02 23:46:37 by Mats Holmström Last changed 2010-09-03 09:52:32 by Mats Holmström
