Solar Activity & Ham Radio Propagation
Solar activity affects radio wave propagation by enhancing ionospheric reflection during high activity periods, while low activity diminishes global communication potential. Consequently, ham radio operators must select suitable frequency bands to ensure successful communication.
Amateur radio operators use solar indices to predict radio wave behavior and adjust communication strategies.
See for example the following banner courtesy of Paul L Herrman, N0NBH:
The banner displays numerical indices, which are explained below:
SFI - Solar Flux, 2800MHz (10.7cm)
(SFU units) correlates with F2-region ionization; higher value better HF conditions.
(SFU units) correlates with F2-region ionization; higher value better HF conditions.SN - Daily Sunspot Number is a measure of the solar activity; like SFI it correlates with enhanced F2-region i.e. better HF conditions
K-Index: Geomagnetic Disturbance; good conditions K < 3 | A -Index: 24 hours Average; good conditions A < 10
: Geomagnetic Disturbance; good conditions K < 3 | A -Index: 24 hours Average; good conditions A < 10304 Å: Total Solar Radiation SEM (Solar EUV Monitor) wavelenth: 304 Ångstroms (30.4nm) that affects F-region ionization
Ptn - Proton Flux Density | Elc - Electron Flux Density in the Solar Wind;
both impact E-region
Aurora indicates the strength of the ionization of the F-region in the polar regionsMUF Boulder - Maximum Usable Frequency (MHz) at Boulder, CO, USA, updated every 15 minutes.
Read more about Solar Activity & Ham Radio Propagation
The project "Understanding HF Propagation" provides a detailed overview and tutorials on HF propagation.