Magnetars and the Chiral Plasma Instabilities

We propose a possible new mechanism for a strong and stable magnetic field of compact stars due to an instability in the presence of a chirality imbalance of electrons—the chiral plasma instability. A large chirality imbalance of electrons inevitably occurs associated with the parity-violating weak process during core collapse of supernovae. We estimate the magnetic field due to this instability to be of order 10 G at the core. This mechanism naturally generates a large magnetic helicity from the chiral asymmetry, which ensures the stability of the large magnetic field.