  We propose a new mechanism for electroweak baryogenesis based on
gravitational waves generated by helical magnetic fields that are present
during a first order electroweak phase transition. We generate a net lepton
number through the gravitational chiral anomaly which appears due to the chiral
gravitational waves produced by these magnetic fields. The observed value of
baryon asymmetry can be obtained in our mechanism within parameter space of
scenarios with an inverse cascade evolution for magnetic fields which can also
be candidates for large-scale magnetic fields.
