Where is the sun in its current 11-year solar cycle?

The sun is powered by the nuclear fusion of hydrogen to helium, deep within its core. Above the sun's surface, however, a different force dominates: electromagnetism. This force is responsible for sunspots, solar flares and coronal mass ejections (CMEs).

These processes follow the solar cycle, an 11-year cycle of increasing and decreasing activity on the sun when the sun's magnetic field exhibits a full magnetic reversal. At the trough of the solar cycle, sunspots are sparse, and subsequent solar flares and CMEs — which typically originate from sunspot regions — can be absent for months at a time. This phase of the solar cycle is called solar minimum, which is in stark contrast to solar maximum, the peak of the sun's 11-year cycle of activity.

Officially, solar maximum is defined as the peak month of a given solar cycle, based on monthly sunspot numbers. More specifically, it is not defined by the month that had the most sunspots but by the peak of a "smoothed" sunspot number, obtained by averaging monthly sunspot numbers over a 13-month period. However, although solar maximum is defined by this peak in smoothed sunspot numbers, the term "solar maximum" is colloquially used to define the extended period of two to three years around the peak month, when solar activity is generally high.

Related: The sun might've just had a record-breaking number of visible sunspots

Solar cycles follow a numbering system that began with Solar Cycle 1 in 1755. We are currently in Solar Cycle 25, which started at solar minimum in December 2019. This solar minimum period can be seen in the image above.

That same year, a joint panel of the National Oceanic and Atmospheric Administration (NOAA), NASA, and the International Space Environment Service (ISES) released an official forecast for Solar Cycle 25. The prediction was not based on a single model but rather on the average of multiple simulation and model runs. The outcome was a prediction of a relatively weak solar cycle, in line with what we experienced during Solar Cycle 24 (which peaked in 2014).

If this prediction were correct, it would put the peak of solar maximum for Solar Cycle 25 in August-September 2025 — now! (This prediction is shown as the red line in the above and below graphs.) So are we currently at solar maximum?

No! Solar cycles are not exactly 11 years long; they can range from around nine to 13 years. Stronger solar cycles — those with a higher sunspot peak — tend to be shorter in duration, and weaker solar cycles are usually longer. This means that if Solar Cycle 25 were stronger or weaker than predicted, the peak month of solar maximum would drift from this August-September 2025 prediction.

And this is exactly what has happened: As early as 2022, it became clear that the current solar cycle was outperforming the NOAA/NASA/ISES panel's predicted sunspot numbers. We saw strong peaks in the sunspot numbers in the summers of 2023 and 2024, accompanied by a rise in the 13-month smoothed sunspot numbers.

The current peak of this smoothed curve (purple in the above graphs) occurred in October 2024, the current solar maximum of Solar Cycle 25. Since then, solar activity has been declining, with a particularly stark drop in May of this year. It is therefore possible — and perhaps even likely — that October 2024 will end up being the month of solar maximum, preceding the NOAA/NASA/ISES prediction by 10 months.

If this is true, then we are past the peak and moving toward the declining phase of the solar cycle. During this phase, there are fewer sunspots, but large flares and CMEs are still possible. Historically, the largest flares of a solar cycle are common during this period.

It is, however, impossible to say for certain just yet. We will likely see further spikes in solar activity this cycle, but perhaps not to levels exceeding the average values in October 2024. It's not possible to know when sunspot numbers might take another turn. Typically, we cannot identify solar maximum (or minimum) with certainty until a year or two after it has passed.

In terms of solar activity, the first half of August was uneventful, with very few sunspots. This changed toward the second half of the month, when large regions of sunspots rotated into view. These regions produced few notable solar flares, but they launched a CME at Earth, triggering a geomagnetic storm on Sept. 1-2. Further solar flares from these sunspot groups will remain visible to Earth for another week.