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(meteorobs) Trains in dim, fast meteors?
Another unusual (albeit quiet) event this weekend was that I noted in my log a
4.5 magnitude Leonid with a long wake! (I.e., a train somewhere just below 0.5
seconds.) Being aware of the 3rd magnitude rule-of-thumb "cutoff" for meteor
trains, I was very surprised by this! The train actually appeared nearly as
bright as the meteor, and left a very clear impression.
What exactly is the reasoning behind the 3rd magnitude cutoff? Is it because of
the difficulty of detecting fainter ephemeral extended objects with the eye? Or
are there actual physical explanations that make smaller material in a stream
(i.e., meteoroids resulting in dimmer meteors) unlikely to produce trains?
If its the former, then significant variations in individual perception and in
observing-site transparency would certainly come into play. If the latter, then
wouldn't geocentric velocity (e.g., 72 km/s) also be a factor in determining how
small a particle would result in a train. Just curious,
Lew