POSSIBLE DETECTION OF METEOR STREAM EFFECTS ON THE LUNAR SODIUM ATMOSPHERE

We report two sets of observations of sodium emission from the lunar a tmosphere. The spectra were taken on two nights having very similar lu nar phases, at various distances from the limb. Using Chamberlain's mo del of the exosphere, we obtained values of the temperature, scale hei ght and number density at the surface. These values differ significant ly between the two nights. The spectra of the first night were taken w hen the Earth-Moon system was entering the Leonid meteor stream and sh ow a marked increase in intensity, temperature and scale height relati ve to those of the second night, and relative to data for similar luna r phases published in the literature. We believe that this increase is related to an enhanced flux of micrometeoroids associated with the Le onid and possible with the Taurid meteor streams. The micrometeoroid c omponent is generally considered the least important contribution to t he sodium flux, and its distribution is assumed to be isotropic. We ha ve previously suggested that an anisotropic and enhanced micrometeor c omponent could be associated with meteor streams. The results reported below support this suggestion. (C) 1998 Elsevier Science Ltd. All rig hts reserved.