In my last message to this reflector, I said
> Thus all I'm saying is that the mid and high latitude ionosphere is
> not any higher than what our models say. And I'm sure ionosonde data
> would confirm this.
Again, the issue is not if the ionosphere moves up and down over a solar
cycle. It does, and that is understood and documented. The issue is
whether the worldwide ionosphere has moved to a lower (or higher)
altitude over the past decade or so to explain why extremely long
distance 160m DXing during this solar minimum is not as good as the last
solar minimum (1995-1997). The idea that the ionosphere is lower comes
from the recent press releases about a lower-than-expected equatorial
ionosphere.
Identifying long term trends in the ionosphere has been a hot button in
the scientific community, as scientists are trying to understand the
long term effects of increased greenhouse gases and changes in the
Earth's magnetic field (change in intensity and movement of the magnetic
poles). The results of these studies show the global height of the F2
region peak (hmF2) has decreased by about 2.5 km over the past 50 years,
which implies it has decreased by about 0.5 km since the last solar
minimum. We have to watch it here, though, as this global trend is the
average of the trend of individual ionosonde stations - some stations
show an increasing trend in hmF2, some show no trend, and some show a
decreasing trend in hmF2. In other words, the worldwide ionosphere is
very dynamic, and is not necessarily consistent at all locations in its
long term trends.
Thus I stand by my original comment - that the lower-than-expected
equatorial ionosphere in the press releases does not translate to a
lower mid and high latitude ionosphere due to fact that there is a
unique process at equatorial latitudes that does not manifest itself at
mid and high latitudes. To view a recent (15 December 2008) PowerPoint
presentation of these measurements by the scientific groups responsible
for this experiment, view the file at
www.nasa.gov/pdf/296963main_cnofs_CINDI_Final.pdf. It's an 8.5 Meg file.
Carl K9LA
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