The Leonid meteor shower and the lunar sodium atmosphere

Observations of lunar sodium were made on November 16-18, 1997, at Asiago and Mount Lemmon Observatories. A small enhancement was observed, and we suggest that it was related to the Leonid shower. Visual observations by members of the Association of Lunar and Planetary Observers and the North American Meteor Network show a peak, a few hours wide, at about 12:50 UT on the 17th. The possible enhancement of the lunar Na appears to last at least 3 days, and must be associated with a considerably more extended cloud of particles 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 atmospheric observations, but if the extended, faint shower is also enhanced the corresponding lunar Na should be observable for a considerably longer period. Key Words: Moon; atmospheres, structure; meteors.