Strong influence of lunar crustal fields on the solar wind flow

Abstract

We discuss the influence of lunar magnetic anomalies on the solar wind and on the lunar surface, based on maps of solar wind proton fluxes deflected by the magnetic anomalies. The maps are produced using data from the Solar WInd Monitor (SWIM) onboard the Chandrayaan-1 spacecraft. We find a high deflection efficiency (average ~10%, locally ~50%) over the large-scale ( > 1000 km) regions of magnetic anomalies. Deflections are also detected over weak ( < 3 nT at 30 km altitude) and small-scale ( < 100 km) magnetic anomalies, which might be explained by charge separation and the resulting electric potential. Strong deflection from a wide area implies that the magnetic anomalies act as a magnetosphere-like obstacle, affecting the upstream solar wind. It also reduces the implantation rate of the solar wind protons to the lunar surface, which may affect space weathering near the magnetic anomalies.