The solar cycle describes an approximately 11-year cycle of solar activity driven by the sun's magnetic field and indicated by the frequency and intensity of sunspots visible on the surface. Solar cycles are repetitive yet difficult to predict. A cycle can be as short as eight years or as long as 14 years and varies dramatically in intensity. The current cycle — solar cycle 25 — began in December 2019, according to a solar cycle 25 article from NASA. Solar activity is expected to ramp up until the predicted solar maximum in 2025.