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Re: (meteorobs) Leonids 2000



Okay, Joe, understood, but I rather thought there should be no doubt
about the reality of dust trails.  However, I guess that is not for
me to judge.  The only question in my mind was in the calculation of
the rates.  If you refer to Fig 9, of our original article, you will
see that the year 2000 is the first year in the last 200 years that
two substantial outbursts are possible in the same year (use ZHR0).
There is thus no reason to be surprised by the lack of any precedent.

Having read Upton in the last several months, it is apparent that he had
a clear understanding of the dynamics involved and appears to have
been the first to come up with dust trail calculations for the Leonids.
Dust trail calculations for the Draconids predate Upton however.  All the
dust trail calculations I've seen by different authors have agreed within
minutes. Methods using averaging of many test particles sometimes differ
due to the binning over time and space being too coarse.  The direct dust
trail calculation overcomes this by making a few iterations of a single
particle.

Perhaps it appears arrogant to some, but it was clear to David and I that
the dramatic correspondence of the time of maximum (within about 5 minutes)
from dust trail calculations for the Leonids in 1866, 1867, 1869, 1966 and
1969 and that independently determined by Peter Brown from historical
observations of these Leonid storms and short duration outbursts, was not
due to chance.  There were no discrepant timings.  In our view, questioning
this was questioning Newton, and the situation was never in doubt in our
mind.  The time of maximum in 1999 came as no surprise to us.  Just what is
required?  If nothing much happens this year, will such uncertainty
remain for another year?  I had assumed the test being suggested was of the
dust trail density model which is independent of the, in our view, well
confirmed dust trail theory.  The dust trail theory has been independently
"discovered" numerous times simply because it is relatively straight
forward to conceptualise and requires, in its most basic form, only
Newtonian dynamics.

Cheers, Rob

Robert H. McNaught
rmn@aaocbn.aaodot gov.au

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