From: James Brown (jim_at_Seti.Net)
Date: Sat Mar 05 2005 - 18:42:42 PST
I guess I'm confused.
When we have a lightning storm in San Diego (very rare occurrence but one is going on now) I hear/see bursts in the water hole, on HF, UHF and everywhere else I care to tune. Lightning discharges seem to be very broad band. I of course have no way to detect X rays.
www.SETI.Net
Jim_at_SETI.Net
W6KYP
Argus station DM12jw
----- Original Message -----
From: MarcusJohn_at_AOL.COM
To: public_at_setileague.org ; argus_at_setileague.org
Sent: Thursday, March 03, 2005 3:14 PM
Subject: SETI public: Lightening emissions: Xrays.
I have here a citation from Geophysical Review Letters, 16 Jan 2005. It is at the bottom.
One of my pet theories is that lightening on foreign worlds ought to be detectable.
Now we have evidence that lightening emits xrays.
I think it is possible that lightening emits in the water hole as well, since it seems
to emit in a lot of different frequencies.
If anyone would like to test my theory, then if they have a lightening storm within
the line of sight, see if they can turn their Argus station towards the storm and
see what the electronic signature of the storm is in the water hole.
The storm has to be in the line of sight because these frequencies are not observable
over the horizon.
Please be careful. Turn the gain down at first, or take the LNA out of the circuit,
and turn everything off if the storm
is within 20 miles, so you don't get hit by the bolts.
This obviously puts large constraints on the local topography of the Argus station.
You cannot do this if you are deep in a valley because you cannot see 20 miles
to the horizon. Only Argus stations on a hill will be able to do this.
Any comments? This might be an interesting project, and it may be publishable if we
get good data.
John.
X-RAY THUNDERBOLT. Scientists have long suspected that lightning
might generate x rays. However, until recently the observation of
such x-rays has remained elusive, largely owing to the unpredictable
nature of lightning. In the last few years a series of experiments
by Joseph Dwyer and his colleagues at the Florida Institute of
Technology and the University of Florida has shown that lightning
indeed emits large bursts of x rays with energies up to about 250
keV (about twice that of a chest x ray). These x rays are mostly
produced not by the bright return strokes, but by the leaders that
precede the stroke, as they propagate from the cloud to the ground.
Now, Dwyer and his colleagues have discovered that these bursts of x
rays are produced at the precise moment that the lightning steps
forward along its jagged path. For unknown reasons, lightning does
not travel to the ground in a continuous manner, but instead
traverses the distance in a series of discrete steps. It is this
stepping process that gives lightning its jagged, sometimes forked,
appearance, and Dwyer has now shown that this same stepping process
also makes x rays. The x rays are likely produced by strong
electric fields that accelerate electrons to close to the speed
of light. These so-called runaway electrons collide with air
producing bremsstrahlung ("braking radiation" in German) x-rays.
Dwyer says that higher energy gamma rays are also emitted sometimes,
but that these seem to come from the thunderstorm cloud itself and
not from the lightning stroke. (Dwyer et al., Geophysical Review
Letters, 16 January 2005.)
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