[meteorite-list] spiraling meteors

From: Marco Langbroek <marco.langbroek_at_meteoritecentral.com>
Date: Thu Jul 15 19:02:43 2004
Message-ID: <000d01c46abf$cea78780$9600000a_at_HAL>

We just had a discussion on this on the meteorobs list (www.meteorobs.org -
and then the July archive).

I do not believe in spiraling meteors at all, and in 15 years of dedicated
meteor observations never saw one. I think all of these reports stem from
two origins: one is fragmenting meteors where fragments move off in slightly
different angles, creating a zig-zag illusion. The other, and I think the
main source, is that the persistent trains of meteors start to show
corkscrew patterns often almost immediately after formation - creating the
illusion that the meteor itself corkscrewed as well.

> Personally during the surprise -pre 17 hours - of the Leonids
> in 1998, I saw one strong meteor, maybe -8 mag., that was split
> in two AND both of them giving of strong light and both most
> clearly corckscrewing just as the smoke was leaving the head
> and backwards!

I think this is likely such a case where the corkscrew pattern of the
persistent train created the illusion that the meteor fragments corkscrewed
too.

> I posted this to this list and the meteor list, but nobody
> seems to have made a similar observation. Very few people saw
> that outburst I believe.

You are wrong in that, it was well observed in Europe and Asia. Our group
observed it from the Qinghai desert in northwest China during the 1998
Sino-Dutch Leonid Expedition, see our report in IAU Circular 7052
(http://cfa-www.harvard.edu/iauc/07000/07052.html) and our papers with
photographic results in MAPS. It was very impressive!

> Maybe the fast Leonids (71 km/s) are more prone to spiral,
> though I have seen a lot of Leonids, but just one (two :) )
> that was indeed spiraling.

We have photographed and filmed litterally hundreds of Leonids in 1998, and
other years. None of these shows a spiral motion - but their persistent
trains often do. In fact, I know of no meteor picture by the professional
photographic meteor surveys, that shows corkscrewing of the meteor itself.
If it exists at all, which I doubt, it is very, very rare.

For some photographs of straight Leonid meteors with twisting persistent
trains, see the following pictures by our DMS member Robert Haas:
http://delpsurf.www.cistron.nl/leo2001/photo3.htm (here the first pic shows
the meteor itself, which is straight, and then shows the persitent train,
which twists)
http://delpsurf.www.cistron.nl/leo2001/photo4.htm is another example of
this.

Several twisting persistent trains of Leonids:
http://delpsurf.www.cistron.nl/photons.htm
and:
http://delpsurf.www.cistron.nl/leo2001/photo7.htm

These examples nicely illustrate how the meteor moves straight, but its
bright persistent train starts to twist. While the meteor is gone in a few
seconds or less and catches the casual observer unaware (in case of a
sporadic fireball), such trains can persist for
minutes, and I think it is the twisting character of the latter, which the
observer can see at leisure, that fools observers in thinking that the
meteor itself, which they could not view at leisure, was twisted too. The
twists can start to appear in the second of formation, this process can be
very rapid. And whenever a train lingers, it almost invariably starts to
show these twists. So with regard to the Finnish picture, the twists in the
trail IMHO are no evidence at all that the fireball itself corkscrewed.

- Marco

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Marco Langbroek
Dutch Meteor Society (DMS)
Leiden, the Netherlands
52.15896 N, 4.48884 E (WGS 84)

e-mail: meteorites_at_dmsweb.org
DMS website: http://www.dmsweb.org
priv. website: http://home.wanadoo.nl/marco.langbroek
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Received on Thu 15 Jul 2004 07:02:27 PM PDT