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

[E. L. Jones]

Hello Lew,  Gang.

I understand well the tendancy for the human mind to fill in the blanks 
when it comes to recalling fast paced phenomena.  I'd like to believe 
that I am a bit more experienced observer than the average fireball 
reporter and I try to accurately sense fast moving situations.  I have 
heard a sequence of sounds from a meteor that didn't include a sonic 
boom, a bolide burst, nor electrophonic sounds.

 April 23, 2000 around 3:10 in the afternoon I was in my yard here in 
the Poconos of Pennsylvania and heard the transit of what I believe to 
be a fast moving meteoroid.  I say "heard" because I didn't see it.  
Owing to the fast transit and apparent  25-35° down angle , I excluded 
an aircraft(no engine sound),  rifle bullet (trajectory wasn't flat 
enough) or a part falling from an aircraft (trajectory was too fast and 
not vertical enough) .  The object produced a whoosh sound constantly 
but had an embedded whap.......whap,whap....whap.......whap,whap sound. 
  I presumed this to be a tumbling object with three prominences which 
changed pitch as it tumbled in the slipstream.

As to  potential mechanisms, one which is not likely at play this time 
here is the advance and retreat of a helicopter blade tip can break the 
sound barrier on the forward motion while falling below that threshold 
on the rearward movement.  The result is a series of sharp cracks when 
the conditions are right.  I could imagine a meteoriod in dark flight 
while still supersonic to produce different shock waves if it were tumbling.

I think the category of sound I heard is due to tumbling at high speed.  
A tumbling artillery or mortar canister--after releasing a parachute 
flare, will produce a similar wavering pitch. Shrapnel will also produce 
a distinctive sound.  Large caliber aircraft cannon cases have a 
distinctive sound differing from smaller cases.  In parachute training 
at Ft Benning, the instructors used to guess what was falling from basic 
parachute trainees as they exited the aircraft and lost equipment from 
their packs.  Each category of object, coin, ripcord handle, helmet, 
camera whatever, have different sound signatures. Most everything 
produces a constant whoosh sound.  Anything may produce a series of 
sounds if they are tumbling relatively fast against an airflow( 
turbulent vs laminar flow). Objects down to a foot long or so can be 
heard kilometers from where they are falling.  I believe the ultimately 
we will find that the subsonic (and perhaps supersonic) sounds vary with 
the cross section facing the windward side, peaks and hollows on the surface

So, after what I have seen--I mean "heard"  happen, and taken with other 
reports by close witnesses who reported a whoosh as a meteoroid passed 
near by, I believe that meteoroids can and do produce subsonic wavering 
sounds.  I believe this is technically due to rapidly changing cross 
sectional aspect in the slipstream or in lay terms-- tumbling cartwheels 
like crazy. 

 Now after all this showing off I've done  as I reread your post, is it 
only simultaneous sounds wavering that your comment was about?  Arrrghhh

In that case it still could be due to tumbling if the tumbling changes 
the output of the plasma envelope by deflecting it or uping the output 
as more cross section is stuck out into the stream.  If the 
electrophinics are induced by Radio Frequency (RF) waves chances could 
be that the tumbling is acting on the RF emissions much like tunning an 
antenna etc.

Regards,
Elton

>Date: Wed, 7 Jul 2004 17:55:32 -0400
>From: "Lewis J. Gramer" <lgramer at upstream.net>
>Subject: Re: (meteorobs) Why do some meteors appear to zig-zag?
>
><snip>
>
>BTW, MexicoDoug, I also found your post interesting - although it does raise
>questions in my mind at a couple of points. For one, I noticed that the reports
>you cite mention "sounds" heard during the fireballs witnessed: though there
>is good evidence now that simultaneous or "electronphonic" sounds are in fact
>real observable phenomena, I have never heard any potential mechanism for
>these sounds, which would allow a rotating meteoroid to result in "wavering"
>or otherwise changing sound heard simultaneously on the ground... Does anyone
>else have any information on this particular point?
>
>In fact, if anything, the fact that these sounds are mentioned in the reports
>cited, might SEEM to indicate that the reporting observers were either:
> a) reporting something much closer to them than a meteor, e.g., fireworks;
>or,
> b) very "suggestible", in their recollections of what they observed.
>
>In any case, thanks to all who have posted so far on this thread: during the
>times between major showers, it's always interesting to bring up these old
>chestnuts from past years' debate on 'meteorobs'. :)
>
>Clear skies!
>Lew Gramer
>  
>