Special Session(s) on Radiation Physics

Hi Dave,

I am organizing a special session for the 1997 ACES meeting in Monterey, CA
(17-21 March 1997) and the AP-S Meeting in Montreal (14-18 July 1997) on
"Radiation Physics." A short description of what I have in mind follows
below. I'm sure you could add a great deal to this special session and
would very much appreciate your joining us in Monterey and/or Montreal. If
you know of anyone else who might be interested in this topic, please feel
free to pass this invitation on to them or let me know so that I can
contact them.

If you have any questions or suggestions, please contact me. I look
forward to hearing from you.

Best wishes,

Ed Miller

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I am organizing a special session for the 1997 ACES meeting in Monterey, CA
(17-21 March 1997) and the AP-S Meeting in Montreal (14-18 July 1997) on
"Radiation Physics." A short description of what I have in mind follows
below. I'm sure you could add a great deal to this special session and
would very much appreciate your joining us in Monterey and/or Montreal.

If you have any questions or suggestions, please contact me. I look
forward to hearing from you.

                WHY AND FROM WHERE DOES AN OBJECT RADIATE?

This simple, perhaps deceptively so, question is planned to be the subject
of a special session planned for next year's ACES meeting in Monterey, CA
and AP-S meeting in Montreal, Canada having the working title "RADIATION
PHYSICS." Obviously, Maxwell's Equations have been productively used for
many decades in analyzing the electromagnetic properties of increasingly
complex structures. However, it can be challenging to determine from a
numerical solution that represents the source distribution on some physical
surface just what quantitative contribution each incremental piece of that
source makes to the total far-field power flow. One way to approach this
problem might be to ask, were our eyes sensitive to X-band frequencies and
capable of resolving source distributions a few wavelengths in extent, what
would be the image of such simple objects as dipoles, circular loops,
conical spirals, log-periodic structures, etc. when excited as antennas or
scatterers? A variety of measurements, analyses and computations have been
made over the years that bear on this question. One goal of this special
session will be for contributors to summarize available, relevant data and
observations of which they are aware as well as to offer possibly new
perspectives concerning radiation physics.

It should be noted that an answer to the question "Why does radiation
occur?" is already available from the Lienard-Wiechert potentials which
show explicitly that accelerated charge alone produces a radiation, i.e.
1/R, field. So we should look for accelerated charge in our solutions as
providing the radiation component. This may also not be as easy as it
first appears to be. Places where charge acceleration occurs on a simple
dipole antenna may be fairly obvious after a little thought; at the ends
where the current goes to zero because of charge reflection and at the
feedpoint where the excitation sets the charge into motion. It may also
appear that charge is accelerated along the entire length of the antenna
since the current varies periodically both in time and direction all along
its length. But if the charge is accelerated everywhere, why then doesn't
the total power radiated from a time-harmonic, spatially sinusoidal current
filament increase linearly with length rather than about a mean value that
grows as the Log of the length? This seems to imply that not all parts of
that sinusoid are radiating equally. On the other hand, if all of the
current isn't radiating, is it then necessary to integrate over all of it
to obtain the radiated power? This session is intended to provide a venue
where conventional viewpoints might be questioned and alternate
explanations can be offered without prejudice to encourage an open
discussion of a fundamental question in electromagnetics.

If you are interested in contributing to this special session or have any
questions about what might be an appropriate topic for presentation, please
contact:

Edmund K. Miller
3225 Calle Celestial
Santa Fe, NM 87501-9613
505-820-7371 (Voice and FAX)
e-mail: emiller_at_esa.lanl.gov
Received on Sun Sep 15 1996 - 22:25:00 EDT