The Leonid meteor shower and the Lunar sodium atmosphere

Observations of lunar sodium were made on November 16-18, 1997, at Asiago a nd Mount Lemmon Observatories. A small enhancement was observed, and me sug gest that it was related to the Leonid shower. Visual observations by membe rs of the Association of Lunar and Planetary Observers and the North Americ an Meteor Network show a peak, a few hours wide, at about 12:50 UT on the 1 7th. The possible enhancement of the lunar Na appears to last at least 3 da ys, and must be associated with a considerably more extended cloud of parti cles than that responsible for the bright visual meteors. The circumstances of the 1997, 1998, and 1999 events are discussed. Large showers may occur in 1998 and 1999; the 1998 shower occurs too close to new moon for good atm ospheric observations, but if the extended, faint shower is also enhanced t he corresponding lunar Na should be observable for a considerably longer pe riod. (C) 1998 Academic Press.