  We suggest a new spin orientation mechanism for localized electrons:
$dynamic~electron~spin~polarization~provided~by~nuclear~spin~fluctuations$. The
angular momentum for the electrons is gained from the nuclear spin system via
the hyperfine interaction in a weak magnetic field. For this the sample is
illuminated by an unpolarized light, which directly polarizes neither the
electrons nor the nuclei. We predict, that for the electrons bound in localized
excitons 100% spin polarization can be reached in longitudinal magnetic fields
of a few millitesla. The proof of principle experiment is performed on
momentum-indirect excitons in (In,Al)As/AlAs quantum dots, where in a magnetic
field of 17 mT the electron spin polarization of 30% is measured.
