Topband: long term trends in the ionosphere

[Carl K9LA]

  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