Hi Bill,
Both the solar flux index and the sunspot number are proxy measures
of ionizing extreme ultraviolet radiation, the 10 nm wavelength of
UV radiation that ionizes the E and F layers of the ionosphere.
Solar flux index on the 90s mostly affects the higher frequency
bands, improving 17 and 15 meter propagation during the day and
the 40, 30 and 20 meter propagation at night.
In a few years the solar flux index will begin to persist in the 100s.
This negatively affects 160 meter propagation because of lingering
E layer ionization during the evening and early night time hours. Lingering
E layer ionization blankets and absorbs low angle 160 meter propagation
via the F layer, resulting in significantly weaker and less reliable
160 meter DX propagation.
Higher solar flux numbers will also be accompanied by more frequent
solar flares and coronal mass ejections and much less frequent
coronal hole high speed streams, both of which disturb propagation
on all MF and HF bands through increased absorption.
73
Frank
W3LPL
----- Original Message -----
From: "Bill Stewart" <cwopr@embarqmail.com>
To: "topband" <topband@contesting.com>
Sent: Friday, November 6, 2020 8:23:53 PM
Subject: Topband: Solar Flux Question
Per WWV, the solar flux is at 91. What, if any, affect does this have on
propagation in HF or other
frequency bands....and of course 160 meters. I have seen these geophysical
numbers often, but
never really understood what they meant. The flux has been running in the high
60s/low 70s until
a few weeks ago when I saw it in the 80s.
Tnx de Bill K4JYS
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