[Prev][Next][Index][Thread]

RE: (meteorobs) RE: [Fwd: Fw: RASC List: Fireball Report]



At 10:21 AM 7/1/99 -George K. wrote, in part:
>
>Lew:   Does "... near metallic objects of a certain size or larger" 
>suggest, I wonder, that these radio waves are of extremely long wavelength? 

Yes indeed, and including the 20-20,000 Hz range of frequencies audible to
humans. Colin Keay of the University of Newcastle in Australia has done a
great deal of research on the subject.  His home page:

http://www2.hunterlinkdot net.au/~ddcsk/index.html

>  Wonder if anyone has ever listened for signals from bright meteors and 
>fireballs with one of the VLF or ELF "nature radios?"
>
>George Kelley
>

To answer that, I'm going to borrrow from an e-mail that Jim Richardson
received this week from Stephen P. McGreevy, THE amateur expert in VLF
monitoring:

>As for meteor detection work, I need to emphasize that I HAVE spent
countless hours during major meteor showers (Perseids and Leonids usually)
and many intense but brief minor showers seen deep in dark sky locations in
the western deserts, both monitoring VLF and also monitoring an empty FM
broadcast channel (usually 94.1 or 96.5) or TV video.  Even though the VHF
bands were pinging with strong reflected signals (sometimes for over 1
minute at 96 MHz mimicking an intense sporatic-E opening!) and there were 
*frequent* bright meteors making long trains, nothing but lightning static
prevailed and maybe an odd whistler or two quite apparantly unrelated to
the meteor activity.

>Some VLF monitoring was also done using sensitive loop receivers, besides
e-field whip and wire units. I came to the conclusion that VLF emissions
from the vast majority of meteor impacts (like 99.99%) are far too weak to
be monitored at ground level.  The same conclusion was drawn by a few other
longtime experienced natural radio listeners, of which let me 
emphasize again are quite few.  Any conclusions made otherwise (in
magazine and internet articles, etc.) are NOT from longtime experienced
natural VLF listeners.

This doesn't answer the question of whether a very large event is directly
detectable by VLF, but an experiment to determine if it did would have to
include optical monitoring of the sky to correlate a large event with the
presence or absence of VLF emission.  The only opportunity might be to
piggy-back an experiment onto an existing optical network such as the
European Network, or the BC network that Ed Majden works with.  In any
case, I think it would take thousands of hours of monitoring to get a
definate result.

JB
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html

Follow-Ups: References: