The Sun runs on an internal clock that turns over roughly every 11 years, swinging from calm to turbulent and back again. The current cycle, the 25th since systematic record-keeping began, climbed to its stormy crest — the period called solar maximum — around 2024, and the Sun remains in that heightened, still-active phase as its output slowly begins to ease. During this stretch, dark sunspots, explosive flares, and enormous eruptions of charged gas grow far more common than they are at the cycle’s quiet floor, and their effects reach all the way to Earth in the form of auroras, radio blackouts, and stress on power grids.
An 11-year rhythm written in sunspots
The solar cycle is driven by the Sun’s tangled magnetic field. Over roughly a decade, that field grows increasingly knotted, then reorganizes and flips its north and south magnetic poles before starting the process again. Sunspots — cooler, darker patches where intense magnetic fields poke through the surface — are the most visible scorecard of that churn. Their numbers rise and fall in step with the field’s complexity, climbing from near zero at solar minimum to dozens or more at maximum. Counting sunspots is how astronomers have tracked the cycle for centuries, which is why the peaks and troughs are defined by a smoothed sunspot number rather than any single dramatic event. The 11-year figure is only an average: individual cycles have run anywhere from about nine to fourteen years. They also vary enormously in intensity, with some peaks producing many times more sunspots than others, so no two cycles behave exactly alike.
What solar maximum actually means
Solar maximum is not a single day but a stretch of a year or more when magnetic activity runs highest. It marks the point in the cycle when the Sun’s magnetic poles reverse and when flares and eruptions cluster most densely. Pinning down the peak is inherently backward-looking, because it can only be confirmed once activity has clearly begun to decline. NASA, NOAA, and an international prediction panel announced that the Sun had reached the solar maximum period of Cycle 25 during a briefing on October 15, 2024, formally placing the cycle at its most active phase.
Where Solar Cycle 25 stands now
Reaching maximum does not switch the storms off. In the months after a peak, the Sun stays highly active while its smoothed sunspot number gradually settles back toward calmer levels, a decline that typically unfolds over several years. As of mid-2026, monthly sunspot counts have eased from their highest readings but remain well above the near-zero levels of solar minimum, keeping the Sun in the elevated, still-eruptive part of the cycle, according to NOAA’s ongoing solar cycle progression tracking. In practical terms, the Sun is near the crest of Cycle 25 and only beginning its long slide down the far side.
Flares, coronal mass ejections, and space weather
The most energetic events of the cycle are solar flares and coronal mass ejections. A flare is a sudden flash of radiation from a magnetically active region, capable of reaching Earth in about eight minutes and disrupting high-frequency radio signals on the sunlit side of the planet. A coronal mass ejection is a far larger event: a billion-ton cloud of magnetized plasma hurled into space that, if aimed at Earth, arrives one to three days later. Flares are ranked by their X-ray brightness into lettered classes, with X-class the most powerful, and the strongest active regions can unleash several in a single day. When such a cloud collides with the planet’s magnetic field, it can touch off a geomagnetic storm — the engine behind both the beauty and the hazards of active-Sun periods. The largest such storm on record, the Carrington Event of 1859, set telegraph lines sparking and pushed auroras toward the tropics, a reminder of how severe an extreme eruption can be.
From auroras to power grids: the effects on Earth
Heightened solar activity is felt most vividly in the sky. Geomagnetic storms push the auroras far beyond their usual polar haunts, and during strong events the northern and southern lights have appeared at latitudes that rarely see them. The same storms carry real costs. They can degrade GPS accuracy, force airlines to reroute polar flights away from radio dead zones, increase drag on satellites in low orbit, and, in extreme cases, induce currents in long power lines that threaten electrical grids. The threat is not hypothetical: in March 1989 a geomagnetic storm induced surges that collapsed the power grid across the Canadian province of Quebec, cutting electricity to millions of people for about nine hours. Utilities and satellite operators watch space-weather forecasts closely during the years around solar maximum for exactly this reason.
Why this cycle ran hotter than forecast
Predicting a solar cycle’s strength years in advance is notoriously difficult. The original panel forecast called for a relatively modest Cycle 25, with a peak expected around 2025, but activity climbed faster and higher than that early projection anticipated, prompting forecasters to revise their outlook upward. That gap between prediction and reality underscores how much remains unknown about the dynamo deep inside the Sun that generates its magnetic field. NASA’s visualizations of the cycle illustrate how the pattern of sunspots migrates across the solar surface over time, a behavior captured in the agency’s Solar Cycle 25 imagery, even as the underlying mechanism resists precise long-range forecasting.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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