  In this paper we show a plausible mechanism that could lead to the formation
of the Dark Lanes in Lunar Swirls, and the electromagnetic shielding of the
lunar surface that results in the preservation of the white colour of the lunar
regolith.
  We present the results of a fully self-consistent 2 and 3 dimensional
particle-in-cell simulations of mini-magnetospheres that form above the lunar
surface and show that they are consistent with the formation of `lunar swirls'
such as the archetypal formation Reiner Gamma. The simulations show how the
microphysics of the deflection/shielding of plasma operates from a
kinetic-scale cavity, and show that this interaction leads to a footprint with
sharp features that could be the mechanism behind the generation of `dark
lanes'. The physics of mini-magnetospheres is described and shown to be
controlled by space-charge fields arising due to the magnetized electrons and
unmagnetized ions. A comparison between model and observation is shown for a
number of key plasma parameters.
