How does a higher sunspot number affect HF propagation?
Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies✓Bonne réponse
Lower sunspot numbers generally indicate greater probability of sporadic E propagation
A zero sunspot number indicates that radio propagation is not possible on any band
A zero sunspot number indicates undisturbed conditions
Explication
Sunspot number tracks the Sun's extreme ultraviolet output, and more EUV means a denser F2 region, a higher critical frequency and therefore a higher MUF, so the 10, 12 and 15 meter bands open. The proposed link between a lower sunspot count and sporadic E is wrong because sporadic E is a seasonal E-region phenomenon, not one driven by the sunspot count.