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Re: (meteorobs) Two questions about Leonids 2000
Rob McNaught wrote:
> David and I have never made a bold claim about 2000 and we have never
> said that high rates could not occur. Our analysis, that relies heavily
> on ZHR estimates from the last 200 years. All we can say is that there
> is no historical data that allows us to calibrate our analysis for 2000.
> While we suspect rates will be low, we cannot, and do not, discount
> the possibility for high rates. The situation for 2001 and 2002 is
> rather different. The geometry of encounter is similar to that
> experienced during the last 200 years, so we feel more confident in
> high rates in these years.
Thanks, Rob, for this additional comment on the predictions. As I
just came accross Peter Brown's PhD thesis in my book-shelf, I'd like
to add the result of his study here, too:
Brown used large sets of particles ejected at various perihelion
passages of the Comet, and followed their motion over up to 2000
years. In the big models, about 1 mill. particles are comprised.
This is why he is able to give ZHR predictions based on actual
particle numbers being close the Earth's orbit at the right time.
For 2000, he finds the 1733 ejecta (8-revolutions) to be the
main contributors. He gives an encouter time at 8h20 UT on November
18 (unlike Rob and David: 3h44). The 1866 ejecta (4-rev) are also
involved at roughly 1/4 of the 1733 intensity. For the activity level,
he writes:
"It is probable that a strong shower, and possibly a
small storm, may occur in 2000, but it would likely be smaller
than the 1999 shower. Peak ZHRs in this year are more likely in
the range of a few hundred..."
Now, we should look up what he said for 1999 in order to 'calibrate'
the prediction:
"We tentatively estimate a peak ZHR of order 1000-2000 with a peak
slightly after the nodal longitude of Tempel-Tuttle in 1999."
These sentences give an independent hint on that we will see more
than ZHR=20 this year. Now, make up your observing plans!
Best wishes, Rainer
--
Rainer Arlt -- Astrophysikalisches Institut Potsdam -- www.aipdot de
Visual Commission - International Meteor Organization -- www.imodot net
rarlt@aipdot de -- phone: +49-331-7499-533 -- fax: +49-331-7499-526
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