Lunar conducting islands and formation of a lunar limb shock wave

We propose a mechanism for the creation of a weak solar-wind shock at the lunar limb, in which the fluctuating interplanetary magnetic field interacts with a thin highly conducting crust. The crust is assumed to be fractured and describable in terms of what we call ‘conducting islands.’ The fluctuating interplanetary field produces currents inside the conducting islands, which in turn produce magnetic fields capable of deflecting the solar wind. We find that conductivities of 4×10−4 mho/m and crust thicknesses of 5 km are consistent with the observed 3°–6° flow deflection if the ‘fractionation scale’ is of the order of 400 km. Higher conductivities and greater thicknesses imply a smaller fractionation scale.