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Re: (meteorobs) Bradfields
>I am far from completely familiar with the professional literature,
>but I think this is the first time I have heard of any correlation
>between particle ejection velocities and likelihood of fireballs!
The "ejection velocity" is not a real ejection velocity. The results
(at
least the encounter times) of the various interpretations of the
dust trail theory are quite independent of any ejection mechanism
considered.
In a very simple version of the model you can consider the
displacement of a particle along the trail as a function of
the original ejection velocity, causing a change in the semimajor axis
of the particle' s orbit relative to the comet's (delta a0).
In fact things are more complex. Particles are
ejected at a certain range of velocities. But small particles are
displaced after ejection along the trail by solar radiation
pressure to positons corresponding large delta a0 values,
whereas large particles are not so much affected and remain
where they are, at low delta a0 values. So a kind of
sorting takes place after ejection.
The position at which the earth intersects the trail corresponds
to a certain delta a0 value (or a certain ejection velocity in
terms of the very simple model). If this delta a0 is quite low
and the trail is quite old, you may expect to find only the
larger particles left, the smaller ones having been "blown away".
Having not read the paper I suspect that this was meant.
Hartwig
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