[IRCA] Ionosphere

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

> > I'm far from an expert, but you can have propagation skewed to a more
> > southerly path that avoids the auroral circle. This is noted frequently
> > on HF so I can imagine MW can have this as well.
>
> I've noticed this as well... although the increased geomagnetic activity
> caused expansion of the auroral oval and increased absorption within it,
> more southerly paths that skirt the auroral zone can actually be enhanced.
> Why?  I have no idea. :-)

I have always thought of the ionosphere as a sphere outside the sphere of
the Earth.  It may be that the auroral zone causes a "pimple" in the
ionospheric surface.  As the edge raises, it would reflect signals at a
different angle than parallel planes.  So, the signal would bounce at what
is not a straight line from transmitter to receiver.

It also seems that there must be waves in the ionosphere.  When these waves
coincide properly, it can function as a collating lens to increase signals
much as a dish antenna does. Especially if these waves have a higher
reflectivity.  This may be one mechanism for fading of signals.

There's no reason why the ionospheric layers need be perfectly smooth.  When
they do the ionospheric sounding tests, I wonder if they have a grid of
receivers to see where the strongest signals are?  That could be
interesting.

Craig Healy
Providence, RI


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