Carl K9LA is correct in his assertion that change in height of the
ionosphere in the equatorial region during solar minimum does not translate
to a change in the height of the mid and high latitude ionosphere. However
at and near solar minimum the mid and high latitude D layer of the
ionosphere at mesosphere altitude cools approximately 2 degrees C, contracts
in thickness and signal absorption in the layer increases.
Also a solar flux in the mid 100's is necessary for routine stable formation
of the E Valley/F Layer ducting mechanism. Therefore formation of the duct
is less prevalent at the bottom of solar cycle and long haul propagation
poorer at solar minimum.
73 & GUD DX,
Thomas F. Giella, KN4LF
Lakeland, FL, USA
kn4lf@arrl.net
KN4LF Daily Solar Space Weather & Geomagnetic Data Archive:
http://www.kn4lf.com/kn4lf5.htm
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