Hi Ken,
Of all the long term (more than one year) changes you listed, the
solar cycle is by far the dominant change. Lets hope we see some
energetic solar cycle 25 sunspots this year. None of the cycle 25 spots
we've seen do far have been energetic enough to affect propagation.
73
Frank
W3LPL
----- Original Message -----
From: ktfrog007@aol.com
To: donovanf@starpower.net, cq-contest@contesting.com
Sent: Friday, May 8, 2020 2:29:35 PM
Subject: Long term ionospheric changes (was Magnetic North Pole Drunkard's
Walk)
Hi Frank,
Thanks for your reply. It and the article were interesting and informative.
I did some cursory research last night on long term changes in the ionosphere.
There were a number of articles, most of which provided only abstracts.
Mainly they dealt with the E and F2 layers. Things which could affect them over
time are:
- Long term changes in solar cycles
- Global warming effects, such as the differential expansion and contraction of
atmospheric layers
- Changes in ionospheric chemical composition (due to greenhouse gases)
- Earth's geomagnetic changes (strength, location and orientation).
The practical effects would be changes in the heights of the E and F2 layers
and differences in their refractivity.
I did not find is any discussion of changes in the distribution (i.e., mapping)
of the F2 layer over the globe, but I'm sure it's been studied too in this
regard. I'll have to look further.
Any differences I've noticed since I was licensed in 1958 are anecdotal in my
own mind and therefore not too reliable.
Regardless of any geophysical changes, the biggest change in DXing over the
years has been geopolitical.
73,
Ken, AB1J
-----Original Message-----
To: cq-contest@contesting.com
Sent: Thu, May 7, 2020 10:54 pm
Subject: Re: [CQ-Contest] Russian Beats Out Canada for Magnetic North ... For
Now
Hi Ken,
BBC's article this week " Scientists explain magnetic pole's wanderings"
has attracted the interest of many radio amateurs interested in ionospheric
propagation.
www.bbc.com/news/science-environment-52550973
Unless you've studied geomagnetic physics you probably never learned
-- or even heard -- that the Earth has three north poles. The BBC
article describes the poles very well, but does not address the
relationship between the poles and ionospheric propagation.
The geographic north pole is where the Earth's rotation axis intersects
the Earth's surface in the northern hemisphere. It affects ionospheric
propagation because the orientation of Earth's tilted axis to the Sun varies
with the seasons and determines our daylight/darkness cycles throughout
the year.
While the magnetic north pole -- the focus of the BBC article -- is important
to navigation systems, it has no significance to ionospheric propagation.
Most of us learned about the magnetic north pole when we learned how
to use a compass, it is located in the northern hemisphere where the Earth's
magnetic field lines are measured to be exactly perpendicular to the Earth's
surface. I ts position has been drifting about 50-60 km per year for about the
last forty years.
The geomagnetic north pole -- only briefly described in the BBC article --
is very important to ionospheric propagation and many other aspects of
the Earth's space environment. It is the intersection of the Earth's surface
in the northern hemisphere and the axis of a bar magnet hypothetically
placed at the center the Earth. It is very significant for ionospheric
propagation because it determines the position of the geomagnetic field
in the Earth's space environment including -- very importantly --
its ionosphere. The geomagnetic field very profoundly affects ionospheric
propagation. The geomagnetic north pole drifts only about one km. per year,
a tiny fraction of the movement of the magnetic north pole described in the
BBC article.
https://ichef.bbci.co.uk/news/624/cpsprodpb/13DC2/production/_112164318_new-nc.png
As an aside, while the magnetic north pole is drifting fairly rapidly,
the magnetic south pole is drifting very little at all.
73
Frank
W3LPL
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|
