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" <[email protected]> To: "topband" <[email protected]> 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 _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
