Solar Activity & Ham Radio Propagation
Solar activity affects radio wave propagation by enhancing ionospheric refraction 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 banners to estimate and adjust communication strategies.
See for example the following banner courtesy of Paul L Herrman, N0NBH:
This banner is separated into three sections:
- The left panel displays solar indices (SFI, SN, X-Ray, and 304Å @SEM), geomagnetic indices (A, K Plntry), space weather indices (Ptn Flx, Elc Flx), and other indicators.
- In the middle, there is a "red" image of the current solar corona that represents radiation strength at 304 Ångstrom.
- The right side of the banner displays the calculated HF conditions. The regional conditions vary significanly!
The numerical indices on the left are explained below:
SFI - Solar Flux, 2800MHz (10.7cm) ↗ (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
304 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.
The project "Understanding HF Propagation" focuses on near-real-time indicators and explains what they mean.