(meteorobs) Why do some meteors appear to zig-zag?

Lewis J. Gramer lgramer at upstream.net
Tue Jul 6 16:47:54 EDT 2004


A 'starrynights' post from "Rick M" <starman_962 at ...> reads:
>   I've seen meteors falling almost straight,or with a arch, but to go
> from left to right so to say and back again really tramples the norm
> of physics,either someone was moving well observing this event,(most
> likely in a car but definitly not stationary) or this was something
> else. My two cents...

And "kyle0_3865" <kyle0_3865 at ...> then replied:
> The most spectacular fireball I've ever seen (most likely dumbell
> shaped) split into two pieces and the smaller of the two did a little
> zig-zag number, though it was probably a spiral motion, I only had
> one point of view. My penny, kyle o'glee.....N.Louisiana


FYI, this very question has been discussed at various times on
the global "meteorobs" list over the years. Those with more of
an interest, may wish to browse some of the following posts:
  http://www.meteorobs.org/maillist/msg01162.html
  http://www.meteorobs.org/maillist/msg01164.html
  http://www.meteorobs.org/maillist/msg01176.html
  http://www.meteorobs.org/maillist/msg01197.html
  http://www.meteorobs.org/maillist/msg12771.html

And here are just a few other mentions of "anomalous" meteors:
  http://www.meteorobs.org/maillist/msg01799.html
  http://www.meteorobs.org/maillist/msg08391.html
  http://www.meteorobs.org/maillist/msg18609.html
  http://www.meteorobs.org/maillist/msg18649.html
  http://www.meteorobs.org/maillist/msg21834.html
  http://www.meteorobs.org/maillist/msg21835.html
  http://www.meteorobs.org/maillist/msg21836.html


BTW, Rick is right that physics seems to prohibit meteor trails
actually zigzagging visibly. (Natural) meteoroids enter Earth's
atmosphere at anywhere from 24,000 up to 160,000 miles per hour.

And the vast bulk of visible meteors are caused by particles that
are actually LESS dense than water - from 0.2 to 0.8 g/cm^3. So
just imagine the forces that would be required to cause a zigzag,
moving at 25,000 miles an hour - and imagine them operating on a
particle the size and consistency of a dustbunny... It would not
last more than a tiny fraction of a second before disintegrating!

Of course, denser particles do occasionally enter the atmosphere.
But even the meteoroids associated with "nickel-iron" meteorites,
would be unlikely to withstand the forces involved in a visible
zig zag: remember, you normally see a meteor from a distance of at
least 30 miles up - but more often, hundreds of miles away, unless
it happens to appear quite close to your local zenith. So visible
variations in its path would have to be quite large - and so also
would necessitate huge forces - just to be seen from the ground...


On the other hand, like Michael Gilbreath I too have seen meteors
APPEAR to zigzag. The most notable time I remember was during the
1996 Perseids, when I actually observed TWO different meteors that
appeared to "wobble" during one observing session the peak night:
one could have been called a "zig zag", but the other was closer
to a "curlicue" or even a "braid" - a trail shape that seems even
harder to explain than a zig-zag!


So what is the cause? One key, I think, lies in the fact that we
most often see "zig zags" in faster meteors - Perseids, Orionids,
or that fastest of all major showers, Leonids. These are exactly
the meteors you would think LEAST likely to show any observeable
trail anomalies: after all, moving at 150,000 mph, even a tiny
change in trajectory would wreak havoc on any sort of particle...

But again here's a hint: for these are also the meteors that tend
to be most likely to leave behind "trains" (persistent streaks)!

So we wonder: rather than seeing a zigzag in the actual trajectory
of a meteoroid (let alone a "corkscrew"), is it more likely that
we're actually just observing changes in the path of, or even the
SHAPE of, the ionized column of air left behind by the meteoroid?

Remember that the column of ionized air produced by an entering
meteoroid can be quite thick to begin with - and can also expand
outward from the actual path of entry very quickly. This column
can easily appear (thanks to foreshortening) as TWO paths (i.e.,
either edge of a "hollow cylinder"), which begin parallel to one
another, but can easily be deformed by the extreme winds that are
often found in the upper reaches of our atmosphere. The result of
this, on a time scale of mere fractions of a second, can be what
look from the ground to be "kinks", "zig zags", "curlicues", or
even the rare and stunning "braided paths" occasionally reported.

This possibility was confirmed for me while doing some telescopic
observing in 1999 - when I had the privilege to see a brightish
meteor through the eyepiece, which left behind a train with the
unmistakable appearance of a complex, "pulsating" column - like a
snake that had swallowed several large, variously-shaped creatures
and was digesting them very fast, while "writhing" all the while!


And interestingly enough, the original Australian news story that
started this thread was about a daytime fireball sighting. It left
not merely a traditional glowing train, but an actual debris trail
as well - a "smoke train"! Such a trail would seem like a very good
candidate for high-atmosphere deformations such as described above.

I'd be interested in hearing other readers' thoughts on this topic!

Clear skies all,
Lew Gramer
http://www.meteorobs.org





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