IMO:n sirkulaarit leonideista

 



 

Tässä on IMO:n sirkulaari leonideista, jatkona toinen ja kolmas päivitys, joissa tuloksia 17 / 18 yöltä.:

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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

Observers saw no unusual activity during the nights of
November 15/16 and 16/17, though certains variations in the
activity level require further scrutiny.

Zenithal hourly rates (ZHRs) seem to have risen from about
10 +/- 5 around Nov 16, 0h UT, to about 45 +/- 5 by 4h UT.
After that, the picture becomes less clear. Observers at the
Canary Islands report high rates at the beginning of their
observations, resulting in a peak with ZHR around 110 +/- 20
at 6h00m +/- 5m UT. Activity drops again down to about
65 +/- 20 afterwards, but American observers report average
activity around 100 +/- 10 between 6h45m and 8h30m UT, with
a possible peak around 8h10m +/- 10m of 150 +/- 20. Afterwards, 
activity drops again significantly to 45 +/- 10 by 9h00m UT.

Due caution is needed in interpreting these activity
variation, for the following reasons:

1) Only a few observations contributed to each
   peak. Unexperienced or very perceptive observers can
   "inflate" ZHRs. On the other hand, the peaks cannot be
   explained away by averaging effects alone, as they are
   also noticeable in the individual observations of the 
   observers involved.

2) The bright Last Quarter Moon is a disturbing factor in
   the observations which is not easy to account for
   exactly. Several observers, both in Europe and North
   America, report to have seen their best activity during
   the beginning of their observation. One may speculate the
   continuous hindrance from the bright light of the Moon
   made observers less perceptive for fainter meteors after 
   a while, resulting in a "decreasing peak branch" at the
   beginning of their observations.

If the above-mentioned variations in activity are real,
however, the Nov 16, 6h45m-8h30m UT enhancement in activity
with a possible peak around 8h10m UT may be associated with the
Earth passing the outer regions of the 1932 (2 revolutions
old) dust trail of the parent comet, 55P/Tempel-Tuttle, for
which a possible activity enhancement was predicted at 7h53m
UT by (among others) Asher and McNaught.

The following observers have contributed data immediately
after the event, from which the ZHR profile given below 
has been derived:

Birger Andresen, Joseph Assmus, Neil Bone, Andreas Buchmann,
Marc de Lignie, Petros Georgopoulos, Robin Gray, Rosely
Gregio, Valentin Grigore, Wayne Hally, Zoltan Hevesi, Janne
Pyykkoe, Robert Lunsford, Alastair McBeath, Gilberto Klar
Renner, Josep Trigo, Vishnu Vardhan, Cis Verbeeck, Jean-Marc
Wislez, Ju Zhao, Jin Zhu, Xiaojin Zhu.


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   3h23m     235.076       5         37     40    7
Nov 17   4h47m     235.136       9         74     47    5
Nov 17   6h00m     235.187       3         30    108   20
Nov 17   6h16m     235.198       3         16     66   17
Nov 17   6h30m     235.208       3         11     63   19
Nov 17   7h22m     235.244      11         91     98   10
Nov 17   9h19m     235.322       5         31     45    8
---------------------------------------------------------

ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.

---
Marc Gyssens, 2000 November 17, 16h UT.
wgn@imo.net
---
IMO:n sirkulaarin toinen päivitys:

               LEONID Activity 2000
               ---   2nd update ---
               Update on Nov 16/17
First results on Asian/European observations on Nov 17/18
               --------------------

During the night of Nov 16/17, nothing unusual was seen,
except for two peaks on Nov 17, around 6h UT and 8h UT,
respectively. Additional information indicates that both
peaks are real.  

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. At this time, we have insufficient data to conclude
anything about the predicted Nov 18, 7h51m UT peak.

The Nov 17, 6h00m UT peak of 110 +/- 20 is essentially based
on 2 (non-independent) observations from Tenerife (Canary
Islands). Since our previous release, however, David
Martinez-Delgado and Pablo Rodriguez-Gil, also on Tenerife,
but on a site where cirrus clouds prevented regular
observations, report that they, too, noticed an enhancement
of the activity around 6h00m UT, with approximately 1 meteor
per minute for 10 minutes. 

The Nov 17, 6h45m-8h30m UT activity enhancement (ZHR = 105
+/- 5) with possible peak around Nov 17, 8h10m +/- 10m UT
(ZHR = 150 +/- 20) is in good agreement with a note from
Pavel Koten (Ondrejov Observatory) who detected two peaks
with their backscatter meteor radar, at Nov 17, 8h02m and
8h15m UT, respectively. Tentatively, this period of
increased activity, in particular the peak(s),  may be
associated with the Earth passing the outer regions of the
1932 (2 revolutions old) dust trail of the parent comet,
55P/Tempel-Tuttle, for which a possible activity enhancement
was predicted at Nov 17, 7h53m UT by (among others) Asher
and McNaught. 

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 3h45m
+/- 15m UT. Afterwards, the rates drop again. Whether the
increase in the last line of the table below is genuine,
remains uncertain at this point. Almost all observations
which contributed to this last value were done under very
good sky conditions (apart from the Moon, of course), which
in itself may already suffice to explain this slight anomaly.
It must be emphasized that the Nov 18, 3h45m UT peak in this
broad maximum is not very pronounced. Tentatively, this
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. Whether the end of the
period covered by the table below shows the beginning of a
second maximum, possibly due to 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, remains to be seen.

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, Neha Bhandari, Lukasz Bielun, Lukas
Bolz, Neil Bone, Andreas Buchmann, Marc de Lignie, Frank
Enzlein, Magdalena Gawla, Petros Georgopoulos, Roberto
Gorelli, Robin Gray, Rosely Gregio, Valentin Grigore, Wayne
Hally, Zoltan Hevesi, Tamas Hubay, Javor Kac, Primoz Kajdic,
Akos Kereszturi, Vinit Kulkarni, Zsolt Lantos, Harry
J. Lehto, Robert Leyland, Mike Linnolt, Robert Lunsford,
Alastair McBeath, Norman W. McLeod III, Sirko Molau,
Kiyohide Nakamura, Piotr Nawalkowski, Michael Nezel,
Arkadiusz Olech, Arvid Parnajpye, Natasa Petelin, Szaniszlo
Prohaszka, Nilesh V. Puntambekar, Tushar Purohit, Janne
Pyykkoe, Guo-ming Qin, Gilberto Klar Renner, Kulkarni
Rhishikesh, Victor R. Ruiz, Mikiya Sato, Tomoko Sato, Konrad
Szaruga, Kazumi Terakubo, Mihaela Triglav, Josep Trigo,
Arnold Tukkers, Varada Vaidya, Vishnu Vardhan, George
Varros, Cis Verbeeck, Jean-Marc Wislez, Anna Witas, Oliver
Wunsk, Ju Zhao, Jin Zhu, Xiaojin Zhu.

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  13h15m     235.491       4         35     52    9
Nov 17  19h26m     235.752       7         58     58    8
Nov 17  22h51m     235.896       7        139    106    9

Nov 18  00h26m     235.962       5         30    107   20
Nov 18  01h15m     235.996      11        119    159   15
Nov 18  01h48m     236.019      10        193    213   15
Nov 18  02h16m     236.039      18        377    214   11
Nov 18  02h44m     236.058      16        283    209   12
Nov 18  03h19m     236.083      18        369    220   12
Nov 18  03h47m     236.102      33        493    292   13
Nov 18  04h15m     236.122      29        459    233   11
Nov 18  04h45m     236.143      14        116    225   21
Nov 18  05h27m     236.159      17        416    263   13
---------------------------------------------------------

ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.

---
Marc Gyssens, 2000 November 18, 11h UT.
wgn@imo.net
---


IMO:n sirkulaarin kolmas päivitys:

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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@imo.net
---
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