How does a higher sunspot number affect HF propagation?

Sunspots are strong indicators of overall solar activity. When the sunspot number is high, the Sun emits significantly greater levels of ultraviolet (UV) radiation. This intense UV radiation ionizes the Earth's upper atmosphere, specifically the F region of the ionosphere. Higher ionization levels in the F region allow the ionosphere to effectively refract higher-frequency radio waves (such as those on the 15-meter, 12-meter, and 10-meter bands) back to Earth. This creates excellent long-distance high-frequency (HF) propagation conditions. Options suggesting a zero sunspot number halts all propagation are incorrect because lower frequencies (like 80m and 160m) actually perform very well during solar minimums. Sporadic E is also a localized phenomenon generally unrelated to the 11-year sunspot cycle.