RE: Wireless power transmission (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 21 Jun 2007 10:08:34 +0100
From: Colin Dancer <colind@xxxxxxxxxxxxxx>
To: 'Tesla list' <tesla@xxxxxxxxxx>
Subject: RE: Wireless power transmission (fwd)

Hi Dave,

Glad the description of beta was an aid.  I'll try and take your questions
one at a time, but would welcome peoples' views on whether we're drifting
too far from the list topic and should be taking this discussion off list.

>
> What it indicates to me is that magnetic fields play a role in the field
structure
> of ions.  It seems we could think of ions as beads thrown loosely about.
The ion 
> beta would be the tendency of the beads to be strung together with lines
of 
> magnetic flux.  The ion beta could then be an important factor in
calculating 
> acoustic waves, especially if there is a magnetic flux path between a
transmitter 
> and receiver.

Beta is relevant to plasma waves, but the factors I've previously mentioned
still mean that at atmospheric pressure, even with strong magnetic fields
and ionization from a tesla coil, I still don't believe plasma waves occur
in free air.

> Another way to look at it might be that the most direct path for acoustic
transmission
> of power would not necessarily be a straight line to the receiver.  It
would be necessary
> to understand the magnetic flux paths, particularly with a relatively weak
ion field.  

Static magnetic fields would indeed guide the propagation of plasma waves,
though you must remember that the field from a tesla coil is a) constantly
swapping direction b) loops back on itself to the coil rather than radiating
outwards (we only have magnetic dipoles not monopoles)

> You also brought up an interesting point with regard to the auroras.  The
auroras occur
> in a relatively low atmospheric pressure over a broad space. I would
suspect the ion 
> density in the auroras would be far less than the ion densities near a
Tesla coil, 
> but I could be wrong.  We could use some hard data here.

I'd have to check up on the absolute densities, but the aurora are just the
end points of the journey of solar wind particles trapped in the earth's
magnetic field (mainly electrons are trapped). For most of their journey
they are outside the earth atmosphere, and it is in fact their very low
density which gives a relatively high beta even in the weak geomagnetic
field.  However, the point where you see aurora is in the very high
atmosphere, pretty much as soon as you have an appreciable density of
neutral gas molecules for the electrons to interact with.  Thus in aurora
the ion/neutral density is much much higher than near a Tesla coil.

> You mentioned the effect of neutral particles.  Are you saying that even
though ion 
> densities may be greater near a Tesla coil the high density of neutral
particles 
> causes greater inertial damping than in rarefied atmosphere?

Exactly.  This is pretty much the key factor which ensures you're not going
to get any appreciable plasma waves in free air, and definitely not at
anything like the strengths required to transfer even the most minute amount
of power. Think of the difference between sound propagation in water (fairly
good due to low viscous losses) and treacle (terrible due to high viscous
losses).  

Normal air acts like "ultra-treacle" to plasma waves.

Colin.