Friends in Radio Land-
Not having seen it stated explicitly elsewhere, let me use
Newton's First Law of Motion as a guide and offer the following,
perhaps as Maxwell's "First Law of Ionospheric Propagation":
"Every electromagnetic wave front advances at constant speed
and direction unless it is compelled to change that state by
encountering ionization which is non-uniform over its spatial
extent."
If you disagree with that statement, speak now or forever hold
your peace.
Now, for terrestrial propagation, the ionosphere reveals two types
of non-uniform ionization, its vertical and horizontal electron
density gradients. The vertical and horizontal gradients along the
original wave direction result in great-circle propagation with
hops between the earth and ionospheric regions, including both
chordal hops and chordal ducting from longitudinal variations of
electron density. Horizontal gradients which are perpendicular to
the path will result in propagation away from the wave's original
direction, so-called non-great-circle (NGC) or skewed paths. In
any event, using Maxwell's Equations shows that ionospheric wave
refraction is always away from regions of greater ionization.
For those who feel the need to invoke chordal hops or skewed paths
to explain a short- or long-path contact during quiet geomagnetic
conditions, let me suggest they refer to the International Reference
Ionosphere (IRI) to see if CCIR or URSI models support your contention.
Failing to find the needed gradient, in magnitude and direction, they
should proceed to document the case fully:
1. Date
2. Time
3. Termini for the path
4. Operating frequency and antenna(s)
5. Solar/Terrestrial Indices
6. Proposed Ionospheric Gradient
(geographic location, extent
and electron density variation)
then announce it publicly on the appropriate Reflector and submit
a signed, notarized copy with three (3) technical endorsements to:
Nobel Prize Selection Committee
Royal Swedish Academy of Science
Stockholm, Sweden
Perhaps, with a lot of luck, they might be awarded the Nobel Prize
for Physics by having found a new, unknown region of ionization
and take a place beside Sir Edward Appleton in the history of the
ionospheric research.
73,
Bob, NM7M
--
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