In this paper we present in-situ satellite data, theory and laboratory validation that show how small scale collisionless shocks and mini-magnetospheres can form on the electron inertial scale length. The resulting retardation and deflection of the solar wind ions could be responsible for the unusual "lunar swirl" patterns seen on the surface of the Moon.Miniature magnetospheres have been found to exist above the lunar surface [1] and are closely related to features known as "lunar swirls" [2]. Mini-magnetospheres exhibit features that are characteristic of normal planetary magnetospheres namely a collisionless shock. Here we show that it is the electric field associated with the small scale collisionless shock that is responsible for deflecting the incoming solar wind around the minimagnetosphere. These ions impacting the lunar surface resulting in changes to the appearance of the albedo of the lunar "soil" [2]. The form of these swirl patterns therefore, must be dictated by the shapes of the collisionless shock.Collisionless shocks are a classic phenomena in plasma physics, ubiquitous in many space and astrophysical scenarios [3]. Well known examples of collisionless shocks exist in the heliosphere, where the shock is formed by the solar wind interacting with a magnetised planet. What is a surprise is the size of the mini-magnetospheres, of the order of several 100 km; orders of magnitude smaller than the planetary versions. Results from various lunar survey missions have built up a good picture of these collisionless shocks.These collisionless shocks have a characteristic structure in which the ions are reflected from a rather narrow layer, of the order of the electron skin depth c/ω pe (where c is the speed of light and ω pe is the electron plasma frequency), by an electrostatic field that is a consequence of the magnetised electrons and unmagnetised ions. The narrow discontinuity in the shock structure produces a specular reflected ion component with a velocity equal to or greater than the incoming solar wind velocity. The reflected ions from a counter-propagating component to the solar wind flow that form the magnetic foot region, which extends about an ion Larmor orbit upstream from the shock. This occurs when the Mach number (the ratio of flow velocity to Alfvén velocity) is of the order 3 or less.We have carried out laboratory experiments using a plasma wind tunnel, to investigate mini-magnetospheres

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[1] We report measurements of total path differential phase along a 23 km microwave link in northwest England, in addition to measurements of total path attenuation at 17.6 GHz and 12.8 GHz, with the latter at both horizontal and vertical polarizations. Since the differential phase measurements are one-way, they do not contain backscatter differential phase (unlike radar measurements of differential phase). We show that differential phase is sensitive to atmospheric effects, but that it can help identify both snow and sleet (a mixture of melting particles and rain) near the ground. Additionally, we found that it gave unexpectedly accurate path-averaged rain rates. We also report measurements from a second, 15 km, link operating at 22.9 GHz and 14.1 GHz. There is evidence from this link, which had no topographic constraints on its beam width, that differential phase can be affected by interference possibly caused by scattering from the terrain. The measurements give some information about the path-average drop size distribution being experienced by the link.Citation: Holt, A. R., R. J. Cummings, G. J. G. Upton, and W. J. Bradford (2008), Rain rates, drop size information, and precipitation type, obtained from one-way differential propagation phase and attenuation along a microwave link, Radio Sci., 43, RS5009,