Superflare
Since superflares can occur on stars apparently equivalent in every way to the Sun, it is natural to ask if they can occur on the Sun itself. An estimate based on the original Kepler photometric studies suggested a frequency on solar-type stars (early G-type and rotation period more than 10 days) of once every 800 years for an energy of 10 erg and every 5000 years at 10 erg. One-minute sampling provided statistics for less energetic flares and gave a frequency of one flare of energy 10 erg every 5–600 years for a star rotating as slowly as the Sun; this would be rated as X100 on the solar flare scale. This is based on a straightforward comparison of the number of stars studied with the number of flares observed. An extrapolation of the empirical statistics for solar flares to an energy of 10 erg suggests a frequency of one in 10,000 years.
Solar storm of August 1972
The most significant detected solar flare activity occurred from August 2 to August 11. Most of the significant solar activity emanated from active sunspot region McMath 11976 (MR 11976; sunspot regions being clusters of sunspot pairs). McMath 11976 was extraordinarily magnetically complex but its size was large although not exceptional. McMath 11976 produced 67 solar flares (4 of these X-class) during the time it was facing Earth, from July 29 to August 11. It also produced multiple relatively rare white light flares over multiple days. The same active area was long-lived. It persisted through five solar rotation cycles, first receiving the designation as Region 11947 as it faced Earth, going unseen as it rotated the far side of the Sun, then returning Earthside as Region 11976, before cycling as Regions 12007, 12045, and 12088, respectively.