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(meteorobs) "So what did we learn from the Leonids 2000?"
Here is a short summary of what various people had said before the
2000 Leonids and what they did (and do) predict for 2001 and 2002 -
did I get the latest references from all groups involved?
So what did we learn from the Leonids 2000?
Even though the rich display of the Leonid meteors last month has
confirmed the predictions from the dust trail model in principle,
there are still many open questions - and the forecast for 2001
is still uncertain by an order of magnitude with respect to the
strength of the display. At the moment the detailled behavior of
the 2000 Leonids isn't known yet as not all data are in: It seems
likely (but not certain) that the two maxima of Nov. 18 were up to
1/2 hour "early", and there is some debate whether the 2nd maximum
reached a ZHR of 420 or rather 700 to 800 (as several observers
in North America say).
Three different calculations based on the dust trail model had been
published this year, for 2000 and later years (we won't deal with
other ideas anymore as they failed completely in 2000): by Jenniskens
& al. (Earth, Moon & Planets 82-83, 191-208 and 1-26), by Lyytinen &
van Flandern (ibid., 149-166) and by Asher & McNaught (WGN 28>,
138-143). The three studies take different observed or presumed
effects into account and differ quite a bit in their predicted ZHRs -
the times of the maxima predicted, however, agree to within a few
minutes (UTC; rounded to the nearest 5 minutes below). Here is what
the three groups had to say about 2000 (dashes mean: no prediction
published):
Nov. 17 | 07:50 | 2-rev | Je: 207 | Ly: 215 | As: -
Nov. 18 | 03:45 | 8-rev | Je: - | Ly: 750 | As: 100 ?
Nov. 18 | 07:50 | 4-rev | Je: 70 | Ly: 750 | As: 100 ?
So the first model has the 2nd night way too low and the first one
too high, as has the 2nd which fares better in the 2nd night, while
the third model has all maxima too low. Now here's what our modellers
had to say about 2001 and 2002, respectively, before the 2000 data
were in:
Nov. 18 | 10:00 | 7-rev | Je: - | Ly: 2000 | As: 2500 ?
Nov. 18 | 17:30 | 9..11 | Je: - | Ly: 2700 | As: 9000
Nov. 18 | 18:20 | 4-rev | Je: 72 | Ly: 6100 | As: 15000
Nov. 19 | 04:00 | 7-rev | Je: - | Ly: 4500 | As: 15000
Nov. 19 | 10:40 | 4-rev | Je: 38 | Ly: 7400 | As: 30000
While Jenniskens even in one of his papers says that his extremely low
values for 2001 and 2002 come from "perhaps too simple geometric
considerations", both Lyytinen and McNaught have claimed success
after the 2000 experience. Lyytinen thinks that his rates for 2001
and 2002 may have to be reduced "somewhat", though he still
expects "a good storm for the 4 rev. encounter in 2001."
And McNaught believes that "the storm encounters we predict for
2001 and 2002 will occur within 5 minutes of our prediction and
about a factor of two in the rates." (The EM&P volume represents
the Proceedings of the Tel Aviv conference and is also available as
a shockingly expensive 600-page book.)
[See also http://www.geocities.com/skyweek/mirror/211.html for some links]
Daniel
P.S.: The "shocking" price of the book is $ U.S. 235.-
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