What are Sunspots?

Sunspots are dark areas on the Sun's surface caused by intense magnetic activity.

They vary with the 11-year solar cycle.

When sunspots are abundant it is considered as "Solar Maximum", while "Solar Minimum" means that sunspots are scarce.

The "Solar Maximum" is associated with Sun's magnetic poles reverse. Towards the reversal of the poles, local disturbances are created in the Sun's magnetic field that generate plasma vortices on the Sun's surface. These eddies are regions of colder plasma that appear as dark spots on the Sun's surface.

Sunspot number is an indirect indicator for Solar Activity associated with Regular Solar Emission, sudden flares and erratic mass ejections. The "Solar Maximum" coincides with higher ionization levels that enhance HF radio propagation for long-distance communication. However, during "Solar Maximum" there could be solar storms that can temporarily disrupt HF communication. During "Solar Minimum" sunspots are scarce coinciding with poor HF propagation conditions.

The Understanding HF Propagation Project provides radio amateurs with a detailed overview and tutorials on several aspects of HF propagation.