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(meteorobs) Re: Non-Asherian models bite the dust ?!



Hello Daniel (and others),

As Joe also answered to you Daniel, in fairness the Lyytinen and Van
Flandern model predictions and not those of Asher & McNaught actually fit
the 2000 Leonids best, although the difference with Asher & McNaught is only
one of degree. Both models basically predicted the same peak times and in
that sense therefore turned out to be as correct. But the Lyytinen
predictions were more specific with regard to the strength (ZHR's) than the
Asher & McNaught predictions, and......have proven to be basically correct!
Perhaps even more correct than the first preliminary IMO-analysis mentioned
by Joe might suggest... On my website
(http://homes.dsldot nl/~marcolan/leoY2K.html) you'll find a diagram with rates
I calculated from our Portugal observations and from McLeods data from
Florida (next weekend I hope to add data by Pierre Martin). In these
calculations, and different from the preliminary IMO analysis, I did take
Norman's and our perception in account. The result is a peak probably of
1766 dust near 3:25 UT (Europe) with ZHR ~340; and a peak probably of 1866
dust near 7:20 UT (USA) with ZHR ~700 (higher than the preliminary IMO
result, but please note that there is leeway to either side. Please take
these values as indicating "order of" figures). The latter is what Esko
Lyytinen predicted for that peak, actually. As Joe mentioned, he warned that
his "similar" prediction for the 1766 peak might be inaccurate. That
particular peak amongst others is a section of trail at the edge of a
disturbance by a prior encounter with the earth, and because of its age more
influenced by the mentioned "A2" dilluting effects. Therefore, Esko
specifically noted that rates of the 1766 dust trail might come out more
modest (as they did).
Also note that both the peaks (1766 and 1866 dust trails) seem to have
occurred some 20-30 minutes earlier than predicted by either Asher &
McNaught and Lyytinen. Let's not forget that too, because it was thought
that these times were accurate to better than 10 minutes.....

I do not know whether Lyytinen's model is really "non-Asherian". It is
different in aspects, but as I understood it they also have many things in
common. Anyway, it so far clearly gives as good  results, and maybe even
better, as does the Asher model so your remark that all other models bite
the dust is not entirely correct, I fully agree with Joe about that. I also
would like to note that the Lyytinen model unlike that of Asher supplied a
fairly good prediction of 1999 rates as well; a bit on the high side, but
still better than the other model predictions.

You will find a paper by Lyytinen in the EM&P issue that acts as the MAC
Workshop proceedings, which you should receive as an attendant to that
meeting.

Cheers!

- Marco Langbroek

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