(meteorobs) Meteor colours

[David Entwistle]

Hello again,

I hope you can help me with the following question. If there isn't a
definitive answer, I'd welcome opinions.

During the morning of 19th November, 2002 I took a photograph of a
bright Leonid [1]. When developed, the print shows a distinct range of
colours initially green, then yellow, white and finally orange. As I
didn't notice these colours when I saw the meteor, I put it down to a
peculiarity of the photographic process and thought no more about it.

More recently I came across Alastair McBeath's retrospective poem
'Green-Yellow-Red' [2]. Here Alastair describes seeing these colours
during the 2004 Leonids. 

I've also been reading about the multi-metal Lidar observations of Zahn,
Hoffner and McNeal [3]. In this article they state that, 'Their most
important result is that lidar-observed meteoroids ablate almost
exclusively differentially and not homogeneously'.

I don't fully understand the technicalities of this article, but read it
as demonstrating that the various component elements of the meteoroid
will be lost at different rates throughout the brief life of the meteor.
And, that the rate-of-loss of each element is so significantly different
that they most often only detect one metal element in each meteor trail
illuminated. 

Given that some meteors do appear to show distinct patterns of different
colours, is this differential-ablation recognised as the cause of the
colours - the different colours representing the dominance of one
element's ablation? If so, do we know what metal (or metal ion?) each
colour represents?
 

[1] You can see the picture here, but the colours are more obvious in
the original print - you may have seen better examples elsewhere. 

<http://www.david.entwistle.dial.pipex.com/meteors/Leonids/picture1.htm>

[2] You can read Alastair's poem here.

<http://groups.yahoo.com/group/imo-news/message/1507>

[3] Meteor Trains as Observed by Lidar, by U. von Zahn, J. Hoffner, and
William McNeil. From the book, Meteors in the Earth's Atmosphere - Ed
Murad and Williams. You can also read about other work of the IAP Lidar
here 

<http://www.iap-kborn.de/index_e.htm>
-- 
David Entwistle