On Sun, 7 Jan 2001, Robert Kavanagh wrote:
>
> I, too, find DXAID a very useful tool. One has to remember, though, that
> its auroral maps are derived from mathematical models and are not the
> "real" thing. This is also true of the NOAA auroral maps.
>
Bob,
As for the auroral zones in DXAID, they represent mathematical fits of
auroral data from NOAA, not "models" in any physical or mathematical
sense. But the question of the "real thing" goes back to ionization, not
the optical emissions. There's a difference and we have to make do
with the optical emissions as the ionization is just not measured.
Their origin goes back some years. Dave Evans of NOAA does the auroral
maps on their website and Dave was a former student of mine. Peter was
anxious to do a better job with the auroral maps in DXAID so I got the two
together. Dave gave Peter some of the NOAA data and he then made the
mathematical fits that you see in DXAID.
As for the auroral maps on the NOAA website, one should note the actual
pass that is given and also that the plot is a statistical summary of what
was observed under similar conditions. But the plot DOES NOT mean that
the region is filled up with the ionization. If you have ever seen an
aurora, you will know that there are gaps in the displays and the same is
presumably true of the ionization. A very dynmic situation.
How signals fare in approaching the auroral zone depends on the angle of
approach, glancing or headon. And it all depends on whether the RF is
approaching the auroral zone on the poleward side or the equatorial side.
So life becomes very interesting when the K-index is above 3. One can
just about make a case for any scenario.
73,
Bob, NM7M
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