Original title: Cycle Variation in the Occurrence of Great Soft X-ray Solar Flares
V. N. Obridko, M. M. Katsova, D. D. Sokoloff · September 2026
Scientists know that the most powerful solar flares, which are huge bursts of energy on the Sun, mostly happen near the peak of the Sun's activity cycle. However, researchers wanted to know exactly when and where the biggest events occur. They examined giant X-class flares recorded across four solar cycles since 1975 using satellite data. They tracked flare locations and compared them to magnetic field patterns. They learned that strong flares happen where two separate waves of magnetic activity meet and interact. One wave moves toward the equator, and another moves toward the poles. Relatively weaker X4--7 flares appear at high latitudes of 15 -- 20 degrees, usually 1 -- 2 years before the cycle peak. The absolute largest X10 flares are almost completely missing while the cycle is growing. Instead, they appear at the start of the decline phase and continue throughout the decline as these magnetic waves interact.
You're trying to decide when to cross a busy intersection. You expect the worst traffic right at rush hour, when most people are driving. But the biggest jam often comes an hour later, when the rush-hour crowd meets the reverse flow of cars heading back the other way. Here, the Sun's most intense flares follow the same timing: they rarely appear at the maximum number of dark spots, but arrive just after, when two streams of the Sun's internal motion collide.
Knowing when and where the strongest solar flares strike helps protect satellites, astronauts, and power grids from dangerous radiation. This study shows the most severe flares often appear after the sunspot peak, not during it, and at the boundary where two activity waves meet. That gives forecasters a better warning window for the highest-risk events.
The abstract doesn't state limitations explicitly, but the analysis covers only X-class flares from 1975 onward across four cycles, so it does not address smaller flares or the physical mechanism behind the pattern.
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Cycle Variation in the Occurrence of Great Soft X-ray Solar Flares — V. N. Obridko, M. M. Katsova, D. D. Sokoloff
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.