(meteorobs) What is the FM(FMD)

[YiCao]

Thank you for your answer.But I did not understand it very clearly.In this webside,I read that:
 
http://feraj.narod.ru/Radiants/Predictions/1901-2100eng/Leonids-introeng.html
fM(fMD) - the characteristic of longitudinal density of the trail, it is derived from the time interval between passages of minimal distance to the Earth's orbit by particles with different ejection velocities
 
Is it show that how long  the shower will last? If so,Why do some FM(FMD) is a negative?
 
Best wishes,Yi Cao
 
 
> Date: Mon, 26 Oct 2009 21:27:37 +0600
> From: ast3 at ngs.ru
> To: meteorobs at meteorobs.org
> Subject: Re: (meteorobs) What is the meaning of FM(FMD)
> 
> It is a parameter showing the density of meteor trail. For example,
> FM(FMD) for 1 revolution Leonid trail is ~1.
> 
> Best regards, Mikhail
> 
> Y> I have read this prediction about LEO meteor shower,but I do not understand the meaning of FM(FMD).Dose anybody know it?I very much hope that an answer.
> 
>  --Yi Cao
 		 	   		  
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