Abstract
Distribution of the sodium atoms around Mercury is expected to form the shape elongated toward the antisolar direction, like a comet, due to the solar radiation pressure. It called sodium tail and Potter et al.(2002) identified it for the first time. In this study, we calculated distribution of the sodium tail, especially its cross-sectional profile, by a numerical simulation with the Monte Carlo method. The results of the simulation are compared with that of the observation by Potter et al.(2002) in order to investigate origin of the sodium exosphere. In this simulation, we considered the following three source processes; i.e., photon-stimulated desorption, meteoroid vaporization and solar wind sputtering. We have considered reconcilable production processes which can explain observed the distribution profile and the absolute amount of the sodium emission intensity simultaneously, based on the numerical simulation and expected production rate. As the results, it is suggested that 1)the contribution of the photon-stimulated desorption should be reduced from the expected production rate, moreover, that of the meteoroid vaporization and solar wind sputtering should be increased, and 2)most of sodium atoms at the tail are released from the surface of Mercury by solar wind sputtering.
