  We studied the soft X-ray data of solar flares and found that the
distribution functions of flare fluence are successfully modeled by tapered
power law or gamma function distributions whose power exponent is slightly
smaller than 2, indicating that the total energy of the flare populations is
mostly contributed from a small number of large flares. The largest possible
solar flares in 1000 years are predicted to be around X70 in terms of the GOES
flare class. We also studied superflares (more energetic than solar flares)
from solar-type stars, and found that their power exponent in the fitting of
the gamma function distribution is around 1.05, much flatter than solar flares.
The distribution function of stellar flare energy extrapolated downward does
not connect to the distribution function of solar flare energy.

Solar and Stellar Astrophysics;High Energy Astrophysical Phenomena