November twilight sounding experiments carried out in the Abastumani Astrop
hysical Observatory including the Leonid showers of 1998 and 1999 provided
an opportunity to obtain height distributions of dust of meteoric origin be
tween 20 km to 140 km altitudes. The formation of several dust layers and t
heir subsequent descent and dissipation were observed during these periods.
The layers at 117 km and 54 km were estimated to consist of particles of 0
.01 mum and 21-23 mum radii respectively, according to settling velocities
of these layers. The particle number density at 117 km altitude was estimat
ed to be similar to 30 p cm(-)3.