(meteorobs) Surprising similarity of Meteor streaks & Bolides?

[Chris Peterson]

Hi Larry-

I don't really recognize a distinction between "common" and "uncommon" 
meteors (and I avoid the use of "bolide" completely). There is a 
continuum of meteor events, from barely visible to fragmenting fireballs 
(and to impacts, if you want to take it that far!)

There are at least three important mechanisms responsible for the light 
curve of meteors, and they essentially scale with meteoroid size. Below 
a few centimeters, you have heating from the direct collision with 
atoms/molecules in the atmosphere. Larger bodies heat up due to ram 
pressure. These larger bodies are further segregated by size (and 
intrinsic material strength) into those that remain intact, and those 
that break up, suddenly exposing additional surface area. Of course, 
there is some overlap in these classifications, and some meteors will 
behave unusually.

Categories 1 and 2 typically produce a simple dim-bright-dim profile. 
The third category produces a more complex light curve, with one or more 
flares and often a much more asymmetrical curve overall. Most category 1 
meteors are too dim to trigger cameras that don't use intensifiers. In 
all cases there tends to be some asymmetry simply because the meteoroid 
is in denser air at the end of the path than at the beginning.

You need to be cautious using Limovie to produce light curves. Since 
many meteors (and all fireballs) will generally show saturated cores, 
the curve will be inaccurate. It is a useful tool for quick analysis, 
but you need to do something more complicated if you want an accurate 
curve. I normally fit the meteor in each frame to a Gaussian, and then 
integrate that. This restores the clipped data from saturated pixels, 
and gives a much better indication of the true intensity profile of the 
meteor.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: <stange34 at sbcglobal.net>
To: <meteorobs at meteorobs.org>
Sent: Wednesday, April 30, 2008 10:30 PM
Subject: (meteorobs) Surprising similarity of Meteor streaks & Bolides?


> Perhaps Chris or someone can confirm that common meteors and uncommon
> Bolides have  very similar composite light flaring (SHAPE). Where the
> primary difference is mainly just in light amplitude.
>
> This surprised me when I looked at a limovie graph of a weak meteor 
> from
> last night.
>
> I expected meteor streaks to be completely different with little or no
> flaring variance in the composite shape.
>
> Example:  http://www.geocities.com/stange34@sbcglobal.net/similarity
>
> YC Sentinel