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(meteorobs) Some new insights into the Leonids of 2001 ...

  http://www.astro.uni-bonndot de/~dfischer/mirror/236.html

        Some insights and some mysteries surrounding
                 the pair of Leonid storms

  in November 2001 have emerged in the ongoing analysis
  of the tons of visual and video recordings of the rare event -
  and the latest surprising results have been presented once
  more at the annual meeting of the Arbeitskreis Meteore
  (Germany's Meteor Working Group) in Kühlungsborn.
  Timing-wise the visual and video results agree to within
  minutes - but the relative heights of the »American« and
  the »Asian« storm are more controversial than ever.

  The latest analysis, presented by R. Arlt and S. Molau, is
  based on three sources: the worldwide collection of visual
  observations by several hundred observers (who together
  recorded over 100,000 Leonids), a pair of two identical
  intensified video cameras stationed in New Mexico and
  China - and a continuous 12-hour (!) video recording
  covering both peaks (from dust trails produced by comet
  Tempel-Tuttle 7 and 4 orbits ago, resp.). The latter was
  accomplished by the Japanese amateur O. Okamura flying
  on a regularly scheduled plane from Los Angeles to
  Taipeh (Taiwan). The visual and esp. the video data need
  to be treated carefully for systematic effects, and what has
  emerged after several months of work may still not be the
  final result:

     The »American« maximum consisted of two
     separate peaks 20-25 minutes apart that had about
     the same height (a Zenithal Hourly Rate of some
     1650), although an isolated group of normally reliable
     observers is reporting a much higher 2nd peak. The
     two peaks were at 10:39/43 UTC (derived from the
     visual and combined video analysis, respectively)
     and 11:03/02. The visual data also show possible
     smaller peaks at 9:21 and 12:01 UTC. 

     The »Asian« storm had a sharp peak at 18:16/14
     UTC with a ZHR of some 3750, flanked by two lesser
     peaks at 18:02 and 18:30 UTC - the latter result
     comes from the visual data and is stable, i.e.
     independent of the averaging algorithm used. The
     airborne video data also hint at a pre-maximum at
     17:39 UTC that could be related to a third dust trail,
     9 revolutions old. 

     The relative strength of the two storms is
     unclear at this point: While the visual analysis
     shows the Asian one 2.3 times higher than the
     American one, the airborne video has a factor of 3
     and the pair of groundbased cameras a whopping
     factor of up to 6 difference. That discrepancy is
     probably caused by a strikingly different meteor
     magnitude distribution in the visual and video
     records that in itself is unexplained (the videos show
     far fewer fainter meteors).

  Much work thus remains to be done: While most of the
  reliable visual observers have by now been integrated into
  the worldwide analysis, there were many more video
  cameras in action in the U.S., Asia and Australia. A search
  for local differences (as were seen in 1999, hinting at fine
  structure in the dust trails) or for periodicities (in 1999 a
  strong 7-minute period appeared in Western European
  videos and radar data of the storm) has yet to take place.
  And there is also the question of where to head for this
  year's final possible storm(s) under bright moonlight: Some
  regions in North America, Southwestern Europe and
  Northern Africa look reasonably promising, according to
  cloud statistics compiled by H. Luethen.

  Daniel Fischer - comments and dissenting views welcome :-)
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