Fitting 300 solar flares to sunspot area turns 400 years of records into a superflare estimate

Krivova's own sentence carries the weight here. The fit relating released energy to active-region area was built from the 300 strongest flares between 2010 and 2016 ^[3], roughly 43 events a year ^[1], and she is explicit that no superflare fell inside that window while holding that the statistical relationship "should hold true for more powerful events as well" ^[5]. That is a stated expectation about how stored magnetic energy scales with area, and the entire extrapolation rests on it. Superflares release more energy than trillions of hydrogen bombs and have been observed directly only on distant stars ^[9], so there is no solar data point at the top of the curve to check the fit against.

This method stacks two separate inferences. What 400 years of records contain is sunspot area ^[7]; what a flare draws on is the active region around the spot, the patch where the magnetic field is strong and complex in structure ^[4]. The team reads spot size to get region size, then region size to get eruption strength, and they went looking specifically for the rare high-energy outliers ^[6]. Each hop carries scatter, and the scatter at the top end is where an extrapolated worst case lives or dies.

Looked at closely, the quiet space-age record offers a much weaker constraint than it appears to. Take the once-a-century rate the MPS group reported in late 2024 for stars resembling the Sun in key characteristics ^[12] and apply it to the roughly 70 years in which flare energies have been measurable at all ^[10]: 0.7 expected events, and a Poisson probability of seeing exactly none of about 50 percent ^[2]. Seventy years of nothing is what such a star delivers about half the time. That arithmetic assumes the Sun's own rate matches its peer group's, which is the proposition under test.

Whether a superflare would reach the hardware is a separate question, and the coupling between flare energy and particle damage is far from clean. Damage comes from particles, and Valeriy Vasilyev, lead author of a companion review in the same journal, describes extreme particle eruptions and particularly intense flares as occurring together often, but not always ^[15]. An energy ceiling for the flare therefore falls short of a fluence forecast for the ground.

This whole picture still awaits the number that would anchor it. The phys.org account opens a section headed "The 1947 sunspot benchmark" and its text breaks off mid-sentence on one of the largest sunspots the Sun has displayed ^[8], so the energy the fit assigns to that group, and where that energy sits against superflares measured on other stars, is not on the table. Krivova's own summary of the state of play is that some evidence suggests the Sun can produce superflares at great intervals, with no direct proof ^[18]. On the evidence available, this is a defensible bound on magnitude inferred from a correlation, not a demonstration that the Sun has ever fired one.