In November 1999, light flashes were recorded on the Moon at the peak of th
e Leonid stream activity. It is likely that they were produced by the impac
ts of the stream particles on the lunar surface. In the present work the im
pacts of cometary particles are studied by solving a two-dimensional radiat
ive-gasdynamic problem for particles of different sizes and densities; the
flux of radiation of postimpact hot gas and plasma is calculated, and the l
uminous efficiencies are estimated, as are the sizes of the particles which
could produce the observed flashes.