(meteorobs) IMO Shower Circ.: 2004 Geminids

[RainerArlt]

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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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                  GEMINIDS 2004, visual

A great amount of data has been reported by visual observers 
already one day after the maximum night. The below activity 
profile is based on 5511 Geminids seen by 46 observers.

The peak time of the shower is found near Dec 13, 20h UT.
The time given in solar longitude (position of Earth on its
orbit) is 262.1 degrees which is a bit early in the trend
found by Rendtel (WGN 32:2, 2004) suggesting 262.16-262.17
degrees.

However, variations in the steepness of the magnitude dis-
tributions (population index) as well as additional data
may shift the peak time a bit. These will be studied in
future analyses of the 2004 Geminids. It is very promising 
that already at this early stage of analysis, a detailed 
profile could be constructed. I am very grateful to

 Suzuka Asami (Japan)
 Ricardas Balciunas (Lithuania)
 Andreas Buchmann (Switzerland)
 Ed Cannon (USA)
 Hani Dalee (Jordan)
 Audrius Dubietis (Lithuania)
 Shlomi Eini (Israel)
 George W. Gliba (USA)
 William Godley (USA)
 Vishal Gokhale (India)
 Robin Gray (USA)
 Amir Hassanzadeh (Iran)
 Teresa Hernandez (Argentina)
 Javor Kac (Slovenia)
 Roy Keeris (the Netherlands)
 Richard Kramer (USA)
 Rhishikesh Kulkarni (India)
 Dafna Lavi (Israel)
 Anna Levina (Israel)
 Wei-qi Li (China)
 Alister Ling (Canada)
 Robert Lunsford (USA)
 Jin Ma (China)
 Qiang Ma (China)
 Xiaoyun Ma (China)
 Felix Martinez (USA)
 Bruce McCurdy (Canada)
 Wan-ya Nan (China)
 Markku Nissinen (Finland)
 Juergen Rendtel (Germany)
 Mikiya Sato (Japan)
 Tomoko Sato (Japan)
 Vladimir Slusarenko (Ukraine)
 Huang Song (China)
 Richard Taibi (USA)
 Kazumi Terakubo (Japan)
 Ouyang Tianjing (China)
 Tenho Tuomi (Canada)
 Yi-fei Wang (China)
 Larry Wood (Canada)
 Hao Wu (China)
 Quanzhi Ye (China)
 Kim Youmans (USA)
 Ilkka Yrjola (Finland)
 Wei Zhao (Cina)
 Jurga Zienjute (Lithuania)
 
for their quick and thorough reports. The activity profile
is listed below:

------------------------------------------------------
Date (UT)   Time  Solarlong   nINT   nGEM    ZHR
------------------------------------------------------
Dec 11.622  14:56   259.852     10     78     24  +-  3
Dec 12.333  07:60   260.575     27    240     33  +-  2
Dec 12.916  21:59   261.168     22    242     50  +-  3
Dec 13.062  01:29   261.317     33    314     83  +-  5
Dec 13.169  04:03   261.425     30     91     69  +-  7
Dec 13.249  05:59   261.507     28    141    111  +-  9
Dec 13.294  07:03   261.553     30    212    140  +- 10
Dec 13.351  08:25   261.611     29    166    125  +- 10
Dec 13.681  16:21   261.946     32    452    108  +-  5
Dec 13.776  18:37   262.043     23    102    143  +- 14
Dec 13.793  19:02   262.060     30    144    158  +- 13
Dec 13.816  19:35   262.084     25    137    163  +- 14
Dec 13.836  20:04   262.104     31    168    160  +- 12
Dec 13.857  20:34   262.125     30    183    141  +- 10
Dec 13.886  21:16   262.155     24    149    134  +- 11
Dec 13.905  21:43   262.174     36    257    139  +-  9
Dec 13.924  22:11   262.193     29    174    112  +-  8
Dec 13.945  22:41   262.215     25    257    147  +-  9
Dec 13.969  23:15   262.239     31    254    111  +-  7
Dec 14.013  00:19   262.284     30    304    113  +-  6
Dec 14.091  02:11   262.363     31    248    103  +-  7
Dec 14.145  03:29   262.418     36    124     84  +-  8
Dec 14.182  04:22   262.456     29    102     72  +-  7
Dec 14.233  05:36   262.508     31    108     53  +-  5
Dec 14.276  06:37   262.552     36    150     91  +-  7
Dec 14.322  07:44   262.598     30    372    114  +-  6
Dec 14.410  09:50   262.688     23    342    101  +-  5
------------------------------------------------------

The solar longitudes refer to equinox J2000.0, ZHRs are
computed with a population index of r=2.0 and a radiant
height correction of 1/sin(hR). nINT is the number of
observing periods in the average, nGEM the number of
Geminids involved.


Rainer Arlt, 2004 Dec 15, 10h UT


-- 
Rainer Arlt  --  Astrophysikalisches Institut Potsdam -- www.aip.de
Visual Commission - International Meteor Organization -- www.imo.net
rarlt at aip.de --  phone: +49-331-7499-354  --  fax: +49-331-7499-526