  Ways to give medium- and short-term predictions of solar flares are proposed
according to the statistical analysis of events during solar cycle 23. On one
hand, the time distribution of both C and M class flares shows two main periods
of 13.2 and 26.4 months in this cycle by wavelet analysis. On the other hand,
active regions of specific magnetic configurations and their evolutions give
high productivity of C class flares but relatively low productivity of
energetic (M and X class) flares. Furthermore, by considering the measurable
kinetic features of active regions, i.e., the rotation of the sunspots, some
active regions of specified types are observed to have high energetic flare
productivity, above 66%. The periodicity of the activity revealed can be used
for medium-term C and M class flare forecasting and the high productivity of
active regions forms the basis for short-term prediction of individual
energetic flares.
