  The high 6-Li abundances recently measured in metal-poor halo stars are far
above the value predicted by Big Bang nucleosynthesis. They cannot be explained
by galactic cosmic-ray interactions in the interstellar medium either. Various
pre-galactic sources of 6-Li have been proposed in the literature. We study the
possibility that the observed 6-Li was produced by repeated solar-like flares
on the main sequence of these low-metallicity stars. The time-dependent flaring
activity of these objects is estimated from the observed evolution of
rotation-induced activity in Pop I dwarf stars. As in solar flares, 6-Li could
be mainly created in interactions of flare-accelerated 3-He with stellar
atmospheric 4-He, via the reaction 4-He(3-He,p)6-Li. Stellar dilution and
destruction of flare-produced 6-Li are evaluated from the evolutionary models
of metal-poor stars developed by Richard and co-workers. Stellar depletion
should be less important for 6-Li atoms synthesized in flares than for those of
protostellar origin. Theoretical frequency distributions of 6-Li/7-Li ratios
are calculated using a Monte-Carlo method and compared with the observations.
Excellent agreement is found with the measured 6-Li/7-Li distribution, when
taking into account the contribution of protostellar 6-Li originating from
galactic cosmic-ray nucleosynthesis. We propose as an observational test of the
model to seek for a positive correlation between 6-Li/7-Li and stellar rotation
velocity. We also show that the amounts of 7-Li, Be and B produced in flares of
metal-poor halo stars are negligible as compared with the measured abundances
of these species. 6-Li in low-metallicity stars may be a unique evidence of the
nuclear processes occuring in stellar flares.
