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Topband: Auroral Zone And PMAPS

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Subject: Topband: Auroral Zone And PMAPS
From: (KN4LF, Thomas Giella)
Date: Sat, 29 Dec 2001 00:54:42 -0500
>  ..... not only produce the
> visible aurora but also greatly influence the properties of the
> ionosphere and are connected with strong electrical currents (as much
> as several million amperes) that flow in the ionosphere and connect
> along the geomagnetic field to dynamo processes at high altitude in
> the magnetosphere.....

.....particularly effective in absorbing HF radio signals and can render HF
communications impossible throughout the polar regions......

The government boys are thinking in terms of absorption and unpredictable
refraction of HF not MF frequencies like 160. As K9LA alludes to, absorption
of a MF RF signal extends well south of the visible aurora oval. To look at
the visible aurora oval only, in trying to determine if a higher latitude
propagation path is blocked or open will leave one scratching his head when
the path turns out to be closed. Throw in electron gyrofrequency absorption
and the fact that a 160 signal can actually propagate under the aurora oval
unscathed depending on takeoff angle and signal refraction point and things
can really get muddled.

Thomas Giella, KN4LF

> K9LA wrote:
> >Those pmap pictures referenced by W4ZV, et al, only tell us where
> >visible aurora is likely to occur (low energy precipitating electrons).
>         That's not what NOAA says about the plots Carl...
>                 "How These Patterns Can Be Used

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