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(meteorobs) Leonid storm predictions



I'm heading off on the start of my Leonid travels in about 12 hours.
Hopefully I'll be able to use this time wisely and post the final update
on the storm predictions by David Asher and I.  Our latest assessment
(after correcting for a minor error in the original calculations dust
trail nodal distances of <0.0001 AU) make 1999 less promising :(  The
3-rev trail comes out at ZHR=500, but rates of between 200-2000 are
allowed in the ZHR fit without unreasonable errors in the historical data.
Anyway, David or I will hopefully post the update in the next 12 hours.

In looking at various references to our work, I've noticed a few errors
(like The Aerospace Corporation attributing a ZHR of 1000 for 1998 to the
work of Asher.  Our ZHR fit predicted NO activity from young dust trails.
Only older dust trails and background could be responsible).  S&T for Nov
1999 has a article by Joe Rao.  There are some errors regarding our
work.  The statement

   "David Asher's analysis of meteoroid streams that are three revolutions
    old suggest that 1999 compares somewhat favourably to the
    one-revolution storm of 1833 and the two-revolution storm of 1966."

This is completely wrong in our view and must be Joe's interpretation of
the data.  In the next paragraph, Joe writes that we predict maximum rates
of around 1000-1500 for 2000.  The dust trails in 2000 are hard to predict
due to then lying in a region of our parameter space for which there is no
historical data.  Using some assumptions about the geometry of the dust
trails, we came up with a range of 100-5000 for these trails.  However, as
we note in section 7 of our WGN article, the geometry that gives these
higher rates, would also predict a major storm occurred in 1801.  This is
highly unlikely.  Even a minor storm is unlikely but no data seemed to
exist to confirm or refute this.  In discussing the implications of 1801,
we conclude "This would unfortunately mean that activity in the next
several years would be at the lower end of the predictions."  Our update
is even more pesimistic than this.

BTW, what were the bods at S&T thinking when they wrote (Dec 1999 p115)
referring to the article above
"... Joe Rao explains how the Earth could run smack into a dense swarm of
meteoric particles on the morning of November 18th.  If it does, the
annual Leonid meteor shower could rival, for an hour or so, the awesome
spectacle that greeted observers in the U.S. Rocky Mountains 33 years
ago." 

I don't think you will find Joe (or anyone referred to in the article)
say this at all.

I'll also try to post a review of the various techniques for Leonid storm
prediction that have been published in recent years.

Cheers for now, Rob

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

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