Leonid produced the train shown in Fig. The train was visible by naked eye for 6 minutes after the meteor had vanished. During an effort to observe such a Leonid train using the CAT telescope at ESO, LaSilla, in November 1996, we observed the following brightness evolution of a train that occurred almost in the zenith. During this phase, the train rapidly expands due to thermal expansion until it achieves pressure equilibrium with the surrounding atmosphere. During expansion, one can observe some wrinkling and small scale distortions due to instabilities and turbulence.
Any structure rapidly fades into a diffuse beam of light that splits in two parallel beams.
This is the stage where the emission decay halts and stays constant for as long as 6 minutes for a -5 Leonid, up to half an hour or so for brighter Leonids. Finally, the train intensity suddenly drops and even with binoculars no trace can be observed after this collapse. Hence, during the persistent phase the meteor train appears hollow. The intensity is not centrally condensed. The mechanism that keeps the train luminosity high for such long period of time must involve turbulence or diffusion of hot air in the train and an interaction with the surrounding atmosphere.