Roy:

[snip]
"Roy Lewallen" wrote in message
...
Thanks for the most interesting discussion of slinkys, "ether", and
seismology. But I'm a little vague on what you mean by "vibrations".
You're describing a field whose orientation isn't necessarily at a right
angle (transverse) to the direction of propagation (as in a TE or TM
mode wave), yet whose "vibrations" are nevertheless at a right angle to
the direction of propagation. So the "vibrations" are in a different
direction than the field. I'd like to learn more about this phenomenon,
but I can't find "vibrations" in the indexes of any of my
electromagnetics texts. Do they have another name?

Roy Lewallen, W7EL
[snip]

Vibrations = oscillations

An instance where compressional-dilative waves might occur in
electromagnetic propagation and where those compressional vibrations terms
could be added to the Maxwell-Heaviside equations might be that of
electromagnetic propagation through "light ion" plasmas [ionized gases]
where the ions could physically respond essentially instantaeously to the
passing waves and the distance between ions and hence the media properties
becomes a function of the electromagnetic fields. The effective mu and
epsilon of the media changing instantaneously in response to the propagating
fields, in turn changing the waves, etc... just as for compression acoustic
wave propagating in a compressible gas. This effect is probably
infinitesimal for "heavy ion" plasmas and might be perceptable for "light
ion" plasmas. I wonder if any readers of this NG have any experience with
propagation in plasmas and can share with us if they use
compression-dilutive terms to augment the Maxwell-Heaviside equations in the
analysis.

I presume that the NEC code that you use in EZNEC to integrate the
Maxwellian equations does not support plasma propagation analysis. Perhaps
someone knows of a version of NEC that does. I'd guess that folks at
Lawrence Livermore and at NASA are interested in such problems. I'd be
curious to know if they use augmented versions of Maxwell-Heaviside
equations.

Another, arcane, far fetched, and impractical example of
compressional-dillutive vibrations in em waves that I can think of could be
imagined as a system wherein em waves travel in a waveguide system where the
dimensions of the system [walls of the waveguide] are such that they can
move in and out instantaneously in response to the passing waves thus
alternately confining and expanding the dimensions of the guide relative to
the wavelength of the passing waves, it might be imagined that such action
could induce a wave shortening and lengthening effect on the passing waves
which is what compression-dillution waves are.

Thoughts, comments?

--
Peter K1PO
Indialantic By-the-Sea, FL.

Tom:

[snip]

Yes, "vibes." I think Peter is regressing back to the '60's.
73,
Tom Donaly, KA6RUH
[snip]

Hmmm.... I remember Angela fondly, and how we used to dance to "I just wanna
hold your hand..."

Now just where did I put those old Beatles albums?

--
Peter K1PO
Indialantic By-the-Sea, FL

Peter O. Brackett wrote:
Say did you order your copy of "Entanglement" yet?

I'm going to take a look at it first at the Texas A&M library
hopefully next week.

What is Cecil's wavelength and can I get on it?

Want me to grid dip myself?
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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Thanks for the rundown on "light ion" plasmas, plasma propagation, and
moving-wall waveguides. I only have one remaining question.

Do the "vibrations" of electromagnetic waves you referred to in your
previous post have another name?

Roy Lewallen, W7EL

Peter O. Brackett wrote:
Roy:

[snip]
"Roy Lewallen" wrote in message
...

Thanks for the most interesting discussion of slinkys, "ether", and
seismology. But I'm a little vague on what you mean by "vibrations".
You're describing a field whose orientation isn't necessarily at a right
angle (transverse) to the direction of propagation (as in a TE or TM
mode wave), yet whose "vibrations" are nevertheless at a right angle to
the direction of propagation. So the "vibrations" are in a different
direction than the field. I'd like to learn more about this phenomenon,
but I can't find "vibrations" in the indexes of any of my
electromagnetics texts. Do they have another name?

Roy Lewallen, W7EL

[snip]

Vibrations = oscillations

An instance where compressional-dilative waves might occur in
electromagnetic propagation and where those compressional vibrations terms
could be added to the Maxwell-Heaviside equations might be that of
electromagnetic propagation through "light ion" plasmas [ionized gases]
where the ions could physically respond essentially instantaeously to the
passing waves and the distance between ions and hence the media properties
becomes a function of the electromagnetic fields. The effective mu and
epsilon of the media changing instantaneously in response to the propagating
fields, in turn changing the waves, etc... just as for compression acoustic
wave propagating in a compressible gas. This effect is probably
infinitesimal for "heavy ion" plasmas and might be perceptable for "light
ion" plasmas. I wonder if any readers of this NG have any experience with
propagation in plasmas and can share with us if they use
compression-dilutive terms to augment the Maxwell-Heaviside equations in the
analysis.

I presume that the NEC code that you use in EZNEC to integrate the
Maxwellian equations does not support plasma propagation analysis. Perhaps
someone knows of a version of NEC that does. I'd guess that folks at
Lawrence Livermore and at NASA are interested in such problems. I'd be
curious to know if they use augmented versions of Maxwell-Heaviside
equations.

Another, arcane, far fetched, and impractical example of
compressional-dillutive vibrations in em waves that I can think of could be
imagined as a system wherein em waves travel in a waveguide system where the
dimensions of the system [walls of the waveguide] are such that they can
move in and out instantaneously in response to the passing waves thus
alternately confining and expanding the dimensions of the guide relative to
the wavelength of the passing waves, it might be imagined that such action
could induce a wave shortening and lengthening effect on the passing waves
which is what compression-dillution waves are.

Thoughts, comments?

--
Peter K1PO
Indialantic By-the-Sea, FL.

Roy:

[snip]
Do the "vibrations" of electromagnetic waves you referred to in your
previous post have another name?

Roy Lewallen, W7EL
[snip]

Oscillations perhpaps?

I don't really understand your question... do you object to the term
"vibrations"? What would you prefer, oscillations, or...

It is well known by Physicists that lectromagnetic waves [at least in free
space and isotropic media] are generally consist of only transverse
vibrations,. this type of vibration is inherent in the formulation and
solutions to the Maxwell-Heaviside equations.

For examples of longitudinal or compressive vibratons for instance in a
taught wire like a guitar string, transverse vibrations or oscillations are
side to side, but longitudinal or compressional vibrations would be the very
tiny vibrations in the length of the guitar string. In systems where
longitudinal vibrations are supported, generally the velocity of propagation
of longitudinal vibrations will not be the same as that of transverse
vibrations.

For a detailed explantation of compressional-dilutive or longitudinal waves
in a variety of physical systems, cfr:

William C. Elmore, and Mark A. Heald, "Physics of Waves", McGraw-Hill, New
York, 1969.

--
Peter K1PO
Indialantic By-the-Sea, FL.

No, I'm just trying to figure out how an EM wave can have E and/or H
fields whose directions aren't transverse to the direction of
propagation (as in a lossy medium or in a hollow waveguide) can have
another property of "vibrations" or "oscillations" that *are* always
transverse. The properties of E and H fields that I'm familiar with
include orientation of the field in space, and change in amplitude with
time (which is what I'd normally call oscillations). And, of course, the
orientation can change in time also, as in elliptically or circularly
polarized waves. The property of "vibrations" or "oscillations" that
have a direction different from the direction of the field is new to me.

I notice that you're now qualifying your statement to free space and
isotropic media. Does this perhaps leave open the possibility that waves
in a lossy medium, or bounded within a hollow waveguide, could have
"vibrations" that *aren't* transverse to the direction of propagation?
My original question was in response to your statement that EM waves
were always transverse, regardless of the medium.

Do you perhaps have Krus' _Electromagnetics_, or electromagnetics texts
by Holt, Johnk, Skilling, Magid, Magnusson, or Jordan & Balmain? If so,
perhaps you could direct me to a section which addresses this.

Roy Lewallen, W7EL

Peter O. Brackett wrote:
Roy:

[snip]

Do the "vibrations" of electromagnetic waves you referred to in your
previous post have another name?

Roy Lewallen, W7EL

[snip]

Oscillations perhpaps?

I don't really understand your question... do you object to the term
"vibrations"? What would you prefer, oscillations, or...

It is well known by Physicists that lectromagnetic waves [at least in free
space and isotropic media] are generally consist of only transverse
vibrations,. this type of vibration is inherent in the formulation and
solutions to the Maxwell-Heaviside equations.

For examples of longitudinal or compressive vibratons for instance in a
taught wire like a guitar string, transverse vibrations or oscillations are
side to side, but longitudinal or compressional vibrations would be the very
tiny vibrations in the length of the guitar string. In systems where
longitudinal vibrations are supported, generally the velocity of propagation
of longitudinal vibrations will not be the same as that of transverse
vibrations.

For a detailed explantation of compressional-dilutive or longitudinal waves
in a variety of physical systems, cfr:

William C. Elmore, and Mark A. Heald, "Physics of Waves", McGraw-Hill, New
York, 1969.

--
Peter K1PO
Indialantic By-the-Sea, FL.

Roy:

[snip]
"Roy Lewallen" wrote in message
...
The property of "vibrations" or "oscillations" that
have a direction different from the direction of the field is new to me.
[snip]

That's fine, there are lots of things new to me as well. :-)

These are called longitudinal or compressive-dilutive waves. Such
vibrations do not [usually] occur
with electromagnetic fields, and in the early days of em theory scientists
did wonder if such were
possible, as I have noted in prior postings. However there are numerous
physical systems described
by wave equations which do support both transverse and longitudinal
vibrations of the constituient fields.
I gave several examples in prior postings and you will find lots of such
examples in "Physics of Waves".

[snip]
I notice that you're now qualifying your statement to free space and
isotropic media. Does this perhaps leave open the possibility that waves
in a lossy medium, or bounded within a hollow waveguide, could have
"vibrations" that *aren't* transverse to the direction of propagation?
[snip]

The point is not that the waves have "vibrations" that are transverse to the
direction
of propagation. Of course, guided em waves have vibrations which are not
perfectly
perpendicular to the direction of propagation. The TEM mode would not exist
and
TEM waves would not propagate if there were not some potential driving the
waves
forward, meaning that both the E and H fields have some tiny component in
the direction
of propagation. All of this to establish that I do understand em wave
propagation, and to
say that... this has nothing whatsoever to do with longitudinal or
compressive-dilutive
vibrations. The fact that E and H fields "lean" slightly in the direction
of propagation
in a wave guide is not a compressive-dillutive effect on the fields. For
longitudinal
field vibrations to occur the wavelength of the propagating fields has to
change as
it propagates. This does not occur in "normal" em propagation. I
conjecture that
there may however be some exceptions to this, e.g. plasmas, etc... I just am
not
aware of them. Perhaps some other newsgroup reader/poster is more familiar
with any possible longitudinal vibrations of em waves.

[snip]
My original question was in response to your statement that EM waves
were always transverse, regardless of the medium.
[snip]

Roy, I believe that you may be reading too much into the word "transverse",
it
can be used in several contexts. Tansverse vibrations are not compressive
vibrations. With compressive vibrations, the wavelength of the waves
actually
changess it propagates. While in transverse vibrations no such wavelength
changes occur. In this usage the word "transverse" does not refer to
directionality
with respect to direction of propagation, but rather to the fact that the
waves
maintain their wavelegth during propagation. As a "real" example, some
seismic
waves [the so called "S-Waves" in the earth actually change their wavelength
as
they propagate..

[snip]
Do you perhaps have Krus' _Electromagnetics_, or electromagnetics texts
by Holt, Johnk, Skilling, Magid, Magnusson, or Jordan & Balmain? If so,
perhaps you could direct me to a section which addresses this.
[snip]

Roy, yes indeed I have two editions of "Kraus" and I took a course from
Keith Balmain
using his first edition text when I was at U of T.

And...

I can tell you here and now that neither of those two august gentlemen
address the issue
of longitudinal vibrations anywhere in their texbooks! Simply because, as I
have stated in
other postings, Maxwell-Heaviside equations do not support longitudinal
vibrations, and so
why would a text on em waves even discuss such vibrations? The fact that
Kraus and Balmain
do not discuss such things does not surprise me, nor should it you, since
electromagnetic wave
propagation and the Maxwell-Heaviside equations are a particularly simple
example of wave
motion.

Roy if you wish to deeply understand wave equations and wave motions and to
understand
the wider ramifications of wave motion, you just gotta read more widely in
the "Waves"
literature.

Kraus and Balmain are very narrow in scope, being confined strictly to em
waves!

If they had attempted to include any "early" history of em research from
around the middle
of the 1800's then they would have outlined some of the early speculations
by contemporaries
of Maxwell, such as Kelvin, Heaviside and others as to the possibility that
Maxwell might have
left longitudinal terms that might have proved significant, of course they
were found never to be
needed. However even back in those times most Natural Philosophers [They
were'nt called
Physicists in those days] and Electricians like Heaviside were more widely
schooled than
today's Engineers and they knew and studied wave equations in their full
glory... longitudinal
vibrations included. These days however our electrical engineering
education is far too narrrow
and does not expose folks to the wider view of the world. Thus we often
find em wave
mechanics who don't understand longitudinal waves. Until I became involved
in underwater acoustics and seismic propagation problems and saw the wave
equations in
their full glory, I too had a narrow view of wave mechanics.

I don't know if Kraus or Balmain ever encountered the "full" wave equations,
but in any
case their texts are directed at em specialists and so their narrow view is
not surprising.

As I posted before, if you are interested in such things, check out:

Elmore and Heald, "Physics of Waves" and say, Kennett's, "The Seismic
Wavefield" among
others to help you to broaden your horizons on these issues of longitudinal
waves.

--
Peter K1PO
Indialantic By-the-Sea, FL.

Dear Professor David or Jo Anne Ryeburn,

Finally,
I accomplished the study
of this most interesting article...

But, with your permission,
I can not resist to notice that
the key-point of the surprising,
at least to me, introduction
of an ellipse at step (3),
it looks somehow artificial
and in some way opposite
to the intentions of the introduction:

| ...
| don't believe in using calculus
| whenever simple geometry and/or algebra
| makes it unnecessary.
| A proof that avoids calculus can be meaningful for
| those who don't know calculus,
| or who haven't used it for a while
| ...

In all other respects
and as far as I could say something more,
then it is, at least for me,
a perfect argument, indeed!

Sincerely yours,

pez
SV7BAX
TheDAG