Moonlight Cannot Paint the Sky Blue: Evidence for Neutral Solar Wind Atmospheric Excitation

Earth's blue sky has been attributed to Rayleigh scattering for 150 years, yet moonlight—despite identical spectral composition—produces no detectable blue sky. We demonstrate that if scattering dominated, moonlight should create observable blue glow (0.04 lux, magnitude -9.7), contradicting astronomical observations. We propose that blue sky arises primarily from atmospheric excitation by neutral solar wind particles via auroral mechanisms. This explains: (1) the moonlight asymmetry, (2) diurnal color changes matching altitude-dependent auroral emissions, and (3) thermospheric heating at auroral altitudes (85-600 km). This paradigm shift implies neutral particles constitute a significant component of solar wind, with profound implications for solar-terrestrial physics and space weather.