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Re: (meteorobs) pb of population index definition
Hello Jeremie,
I wrote Chapter 7 of the NAMN Guide based on what I had learned from
observing with the International Meteor Organization and from their
handbooks. I will look up the information and see if it provides how they
arrived at that relationship. I haven't seen the Icarus article so can't
comment. But I will forward a copy of your email to both Peter and Juergen
to see if they would like to comment.
Clear skies!
Mark Davis
meteors@comcastdot net
----Original Message Follows----
From: Jeremie VAUBAILLON <vaubaill@bdl.fr>
Reply-To: meteorobs@atmob.org
To: meteorobs@atmob.org
Subject: (meteorobs) pb of population index definition
Date: Mon, 15 Jul 2002 14:46:02 +0200
Hello you all !
I have a simple question, dealing with a problem of population index
determination :
In "Meteors showers and their observations", NAMN Guide, chapter 7, we find
:
"r is a value indicating how many more times meteors of magnitude m+1 appear
than meteors of magnitude m. [..] Example : m=4, r=3 => tree times as many
meteors of magnitude 5 appear than meteors of magnitude 4".
I conclude : r = n(m+1) / n(m),
where n(m) is the number of meteors of magnitude m. I call this method
method 1
On the other hand, in "The Perseid meteoroid stream : characterization odf
recent ectivity from visual observations", Brown & Rendtel, Icarus, 124,
414-428, 1996, we can read :
"r=N(m+1)/N(m),
where N(m) is the TOTAL bumber of meteors of magnitude m OR LESS."
Whith this definition, we have :
N(m) = sum(n(m)), with m < smallest magnitude sawn
and r = N(m+1) / N(m)
I call this method method 2.
These 2 definitions are completely different and lead to different value of
r.
Now, lets take a concreate example :
In "Comparison between Leonid meteor shower observation during 1998-200",
PSS,
50, 379-384 (2002), table 2 : lets try to compute r just from the first line
:
m = 4.5 0.5 -3.2
n(m) = 33 10 10
value of r = 1.76
Now the question is : where does this value 1.76 come from ? Is it an
average
value ? I suppose yes, but averaging what ?
Method 1 leads to r = 33/10=3.3 and 10/10=1. average is 2.15
Method 2 leads to r = (33+10+10)/(10+10)= 2.65 and (10+10)/10 = 2. average
is
2.33
So before I ask the author (who is perhaps here...), I would ike to be sure
of
what I am speaking of.
Last question : is it scientificly correct to compute an average value of r,
if
there is not so many meteors, and so a great scattering in the values of r
? I
ask this, because I would like to compute r from our video observations...
Thanks a lot for any answer, and clear skies !
Jeremie
--
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* Jeremie VAUBAILLON
* Institut de Mecanique Celeste et de Calcul
* des Ephemerides (www.bdl.fr)
* 77 Avenue Denfert Rochereau
* 75014 PARIS
* FRANCE
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* tel : +33 (0)1 40 51 22 66
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* URL : http://www.bdl.fr/Equipes/GAP/equipeGAP-JV.html
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