Solar Cycle
Definition
The Sun's roughly 11-year rhythm of rising and falling magnetic activity.
In plain language
Sunspot numbers climb for about five years, peak, then fade โ over and over, roughly every eleven years. Aurora frequency at lower latitudes rises and falls with it.
The science
The cycle reflects the solar dynamo: differential rotation winds poloidal field into toroidal field, spot emergence, and eventual polarity reversal โ a full magnetic cycle spanning ~22 years. Cycle amplitude varies substantially between cycles.
Why it matters for aurora viewing
Knowing where we are in the cycle sets expectations: near maximum, chase actively; near minimum, favor trips under the oval itself.
See this in action on tonight's data.