Ken AB1J asked: Has the magnetic polar drift affected propagation over the
decades??
I'm aware of two papers that have looked at this. They not only looked at
the orientation of the magnetic field, but the strength, too (it is
changing, too).
*Trends in the F2 ionospheric layer due to long-term variations in the
Earth's magnetic field* (Elias, Journal of Atmospheric and
Solar-Terrestrial Physics, doi:10.1016/j.jastp.2009.05.014, 2009).
*Changes in the Earth's magnetic field over the past century: Effects on
the ionosphere-thermosphere system and solar quiet (Sq) magnetic
variation* (Cnossen
and Richmond, Journal of Geophysical Research: Space Physics,
doi:10.1029/2012JA018447, 2013). This paper has a nice image of the changes
in the strength and inclination from 1908 to 2008.
Both papers pointed out that it's tough to separate out the changes in the
F2 region due to changes in the Earth's magnetic field from other stuff
that's going on (greenhouse gases, for example). The best estimate (from
the second paper) is that the height of the F2 region peak has changed by a
couple tenths of a km per decade and the peak electron density has changed
by up to 0.1 MHz per decade.
I think it would be tough to discern these changes in our observations (if
the estimates are accurate!).
Carl K9LA
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