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(meteorobs) IMO Press Release: Leonid Meteor Shower (3rd update)
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I M O S h o w e r C i r c u l a r
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LEONID Activity 2000
--- 3rd update ---
Update on Nov 17/18
Also including American observations
--------------------
During the night of Nov 17/18, a broad maximum is noticeable
with Zenithal Hourly Rates (ZHRs) above 200 between roughly
Nov 18, 1h30m UT and Nov 18, 5h UT, culminating around the
time of the predicted Nov 18, 3h44m UT peak with ZHRs around
300. Around Nov 18, 5h UT, the descending branch of this peak
merges with the ascending branch of a second, equally broad
but somewhat higher maximum with ZHRs above 200 between
roughly Nov 18, 5h UT and Nov 18, 8h30m UT, culminating
around Nov 18, 7h15m with a peak ZHR around 450, about half
an hour earlier than the predicted Nov 17, 7h51m UT peak.
With regard to the Nov 17/18 data, the most striking feature
is the large scatter among individual ZHR values,
doubtlessly due to the disturbing influence of the bright
Last Quarter Moon, which cannot easily be accounted for
exactly. As a consequence, all observations must be
interpreted with great care.
Nevertheless, the averages exhibit a clear pattern. Rates
start rising around Nov 17, 22h UT, and reach values
above 200 from about Nov 18, 1h30m UT onward. ZHRs continue to
rise until they almost reach the value of 300 around Nov 18,
3h45m +/- 15m UT. Afterwards, the rates drop again. Towards
the end of the European observing window, rates no longer
fall and tend to increase again. This increase is matched
with the start of the American observing window which starts
with a steady increase in rates reaching the value of 300
already around Nov 18, 5h30m UT. Rates continue to rise to a
level of 450 around Nov 18, 7h15m +/- 15m UT. Afterwards,
rates drop sharply. Around Nov 18, 10hUT, rates become
comparable with the activity level before the first maximum.
Tentatively, the first maximum may be associated with the
1733 (8 revolutions old) dust trail of the parent comet,
55P/Tempel-Tuttle, for which a possible activity enhancement
was predicted around Nov 18, 3h44m UT by Asher and McNaught.
Similarly, the second maximum may be associated with the
1866 (4 revolutions old) dust trail of 55P/Tempel-Tuttle,
for which Asher and McNaught predicted a possible activity
enhancement around Nov 18, 7h51m UT, although the present
data suggests that this second maximum peaked about half an
hour earlier.
Radar data from Ondrejov Observatory, communicated by Pavel
Koten, and the Leibniz Institute for Atmospheric Physics,
communicated by Ulf von Zahn, confirm the general picture
exhibited by the visual observations. At this time, however,
we do not wish to make strong statements about the precise
positions of the respective peaks of the two maxima, as they
are not very sharp. Nevertheless, it must be mentioned that
several individual North-American observers at very
different locations explicitly reported that they had the
impression the second peak occurred earlier than predicted.
Finally, we wish to observe that many observers mentioned
that the two maxima were rich in bright meteors. Whether
this is a subjective impression or an objective fact can
only be decided from a careful analysis of the magnitude
distributions, which is beyond the scope of these first
releases.
The following observers have contributed data immediately
after the event, from which the ZHR profile given below
has been derived:
Birger Andresen, Rainer Arlt, Adrian Arquiola, Joseph
Assmus, Jure Atanackov, Felix Bettonvil, Neha Bhandari,
Lukasz Bielun, Lukas Bolz, Neil Bone, Michael Boschat,
Andreas Buchmann, Bill Burton, Christian Castillo, Susan
Delaney, Marc de Lignie, Michael Doyle, Frank Enzlein, Yuwei
Fan, Magdalena Gawla, Petros Georgopoulos, Roberto Gorelli,
Lew Gramer, Robin Gray, Rosely Gregio, Valentin Grigore,
Wayne Hally, Roberto Haver, Zoltan Hevesi, Tamas Hubay,
Emmanuel Jehin, Kevin Jones, Tomsilav Jurkic, Javor Kac,
Primoz Kajdic, Akos Kereszturi, Albert Kong, Wen Kou, John
Krempasky, Vinit Kulkarni, Zsolt Lantos, Ken Legal, Harry
J. Lehto, Robert Leyland, Mike Linnolt, Jerry Lodriguss,
Robert Lunsford, Pierre Martin, Jose A.R. Martins,
S. Maticic, Alastair McBeath, Norman W. McLeod III, Huan
Meng, H. Mikuz, Sirko Molau, Kiyohide Nakamura, Piotr
Nawalkowski, Michael Nezel, Dragana Okolic, Arkadiusz Olech,
Kazuhiro Osada, Alexei Pace, Arvid Parnajpye, Natasa
Petelin, Ulhas Pradhan, Szaniszlo Prohaszka, Mayuresh
Prabhune, Nilesh V. Puntambekar, Tushar Purohit, Janne
Pyykkoe, Guo-ming Qin, Francisco A. Rodriguez Ramirez,
Gaurav Rathod, Gilberto Klar Renner, Kulkarni Rhishikesh,
Manuel S. Ruiz, Victor R. Ruiz, Carlos Saraiva, Mikiya Sato,
Tomoko Sato, Miguel A. Serra, Brian Shulist, Yuying Song,
Bjoern Soerheim, Konrad Szaruga, Richard Taibi, Kazumi
Terakubo, Sanjay Thorat, Mihaela Triglav, Josep Trigo,
Arnold Tukkers, Varada Vaidya, Erwin van Ballegoij, Vishnu
Vardhan, George Varros, Cis Verbeeck, Jean-Marc Wislez, Anna
Witas, Jonderko Wojciech, Oliver Wunsk, Dan Xia, Karen
Young, Ju Zhao, Jin Zhong, Jin Zhu, Xiaojin Zhu.
Mark Davis was instrumental in forwarding observations sent
to the Meteorobs mailing list.
Date Time (UT) Sol. long. Intervals Leonids ZHR +-
(2000.0)
---------------------------------------------------------
Nov 15 22h05m 243.848 2 11 13 4
Nov 16 03h33m 234.067 1 7 8 3
Nov 16 21h16m 234.820 6 44 20 3
Nov 17 3h02m 235.062 9 50 33 4
Nov 17 4h53m 235.141 10 74 47 5
Nov 17 6h00m 235.187 3 30 108 20
Nov 17 6h16m 235.198 3 16 66 17
Nov 17 6h36m 235.212 4 22 57 12
Nov 17 7h59m 235.270 10 117 104 10
Nov 17 9h25m 235.330 10 64 44 5
Nov 17 15h00m 235.565 7 74 50 6
Nov 17 19h22m 235.750 14 237 69 5
Nov 17 23h01m 235.903 9 164 102 8
Nov 18 00h27m 235.963 7 62 101 13
Nov 18 01h14m 235.995 15 170 161 12
Nov 18 01h47m 236.018 13 264 219 14
Nov 18 02h17m 236.040 25 496 211 10
Nov 18 02h45m 236.059 24 518 232 10
Nov 18 03h17m 236.082 31 668 236 9
Nov 18 03h46m 236.101 45 809 296 10
Nov 18 04h14m 236.121 41 827 247 9
Nov 18 04h45m 236.143 21 274 218 13
Nov 18 05h13m 236.163 17 440 225 11
Nov 18 05h44m 236.184 11 404 336 17
Nov 18 06h22m 236.211 13 346 337 18
Nov 18 07h12m 236.246 10 547 457 20
Nov 18 07h45m 236.269 15 372 374 19
Nov 18 08h14m 236.289 14 555 272 12
Nov 18 08h40m 236.308 8 133 152 13
Nov 18 09h22m 236.337 9 222 80 5
Nov 18 11h08m 236.411 9 162 42 3
---------------------------------------------------------
ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.
---
Marc Gyssens, 2000 November 19, 2h UT.
wgn@imodot net
---
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