(meteorobs) Re: Geminids time of maximum against magnitude

Lewis J. Gramer lgramer at upstream.net
Fri Aug 20 15:23:49 EDT 2004


Malcolm, your post was a fascinating and informative addition to the
discussion - as always. :) Comments / questions interspersed below.


> -----Original Message-----
>Both radar
> http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1989BAICz..40..288S

I derived two really interesting tidbits from this paper's Abstract:

1) Echo durations in radar (and presumably radio) observations are here
related to PARTICLE SIZE! Some of us on this list have often wondered
aloud, whether there were any functions that could be used to relate the
radio echo duration or "strength" (time and frequency consistency?) of a
meteor with its visual magnitude. And of course, visual magnitude has a
well-known relationship with meteoroid MASS: so here's a statement (that
is presumably supported in this paper, or by other referenced studies?)
that SIZE (which can be related to mass with certain assumptions, if an
average density is known) can be related to echo DURATION... Could this
relationship (if it is actually quantified here or elsewhere), be the
"missing link" relating visual/video with radio/radar meteor observations?


2) The abstract also mentions "The position of the peak in the stream
profiles shifts by - 0.1 deg/meteor magnitude." That was a stimulating
figure to read - a whole magnitude shift in just 2.5 hours!

For after all, this implies that an observer on his or her lawnchair,
if they started early enough and went long enough on the peak night,
could observe this shift in average Geminid magnitude AS IT HAPPENS! :)

This seems even more interesting than the "bright peak after the peak
night" effect. Do any of our most active observers on the list have a
story to relate, of noting this brightness shift during a single night?



>and telescopic data (sorry can't lay my hands on the reference where
>this is reported at the moment) have shown that the fainter meteors peak
>earlier than the bright ones.  There are a number of effects that cause
>this mass segregation.  See Jim Jones's paper
> http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985MNRAS.217..523J
>
>and another by Duncan Steel.
> http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1987MNRAS.226....1O

This last paper from the estimable Dr. Steel also intrigued me - as it
shows that yet ANOTHER physical property of meteoroids and meteoroid
streams can be directly determined from AMATEUR observations - spin!

Clear skies all, and thanks for what continues to be a very informative
and enjoyable "theoretical" thread. :)

Lew Gramer





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