Space Weather 101
🔄 Solar Cycle
What is Solar Cycle?
The solar cycle is the Sun's roughly 11-year pattern of rising and falling magnetic activity, driven by the gradual reversal of the Sun's magnetic field. It swings between solar minimum (few sunspots, fewer flares, generally quiet) and solar maximum (many sunspots, frequent flares and CMEs, and the best odds of strong geomagnetic storms and aurora).
Why it matters
Understanding where the Sun is in its cycle helps forecasters and researchers set expectations for how active space weather is likely to be over the coming months to years — though it says nothing about any individual day or event.
Typical values
Cycles have historically ranged from about 9 to 14 years, averaging around 11. The current cycle, Solar Cycle 25, was predicted to peak around 115 (sunspot number) but has run stronger than the initial forecast, with observed peaks in the 150-160 range.
How scientists measure it
Primarily tracked via the monthly sunspot number, supplemented by other activity proxies like the F10.7 radio flux — both have been recorded consistently enough, for long enough, to reveal the cycle's repeating pattern across centuries.
Why it affects Earth
Near solar maximum, flares, CMEs, and geomagnetic storms all become significantly more frequent, meaning aurora becomes visible at lower latitudes more often, while satellite operators, power grid managers, and radio users all see more space-weather-related disruptions.
FAQ
What solar cycle are we in now?
Solar Cycle 25, which began around December 2019 and is the current, ongoing cycle.
Does solar minimum mean zero activity?
No — even during solar minimum, flares and geomagnetic storms can still happen, just considerably less often than during solar maximum.