1998 CQ WW CW Contest
ZW5B (opr. K5ZD), Single Op 28 Mhz, High Power
Responses to my question on propagation from Brazil.
Your comments about the incredible propagation from down in Brazil,
brought to mind something I read in a book recently. Because of tilt in
the magnetic equator, it turns out that the intensity of the ionosphere
isn't evenly distributed between northern and southern hemispheres (even
at solstice) or even with longitude. There is a region off the east
coast of South America called the South Atlantic Anomaly which is a
Bermuda Triangle of sorts for spacecraft due to the heightened presence
of charge particles in the ionosphere over this region. Perhaps this
might explain why you don't see the same hot propagation when you go to
the equivalent northern latitudes, population concentration
notwithstanding. Check out the following URL for a quick explanation and
a Topex/Poseidon image of the ionospheric electron density (note that it
shows lots of electrons over PY land).
http://tethys.jpl.nasa.gov/discover/electron.html
73 de Mike, W4EF........
The reason that the band stays open all night down there (besides the
fact that it's summer down there so the sun is shining on the ionosphere
above you all day a lot longer than it is here, giving it more
reflectivity once it gets dark) is that the Geomagnetic Equator runs
roughly through Lima, Peru whereas the Geographic Equator runs through
Quito, Ecuador. And for propagation purposes the Geomagnetic Equator is
the important one.
There is also something else going on. When I was in Cordoba,
Argentina as LU5HFI I had to coordinate the visit of a US Navy Earth
magnetic field mapping plane which was spending some time in Cordoba
calibrating the plane's measuring instruments with a local geomagnetic
observatory there before going on to the Antarctic to make measurements.
The scientific crew told me that for reasons that up to that point were
unexplained, the atmosphere over Argentina (and presumably over Southern
Brazil as well) is about 10,000 feet thicker than over any other point
on the globe. I always felt that's why the LUs seem to "own"
10 meters. I am also aware that during the LUs' Sporadic E season in
December/January they routinely have 2 meter short skip openings around
Argentina whereas such openings are pretty rare up here.
de Fred, K3ZO
