Generation of strong magnetic fields in old neutron stars accounting for continuous chiral magnetic effect

Abstract

We suggest a new mean field dynamo model in anomalous MagnetoHydroDynamics (AMHD) accounting for the mean spin (polarization) of the magnetized chiral (ultrarelativistic) plasma of a neutron star (NS). For simplicity we consider a non-superfluid NS with its rigid rotation neglecting also any matter turbulence (convection) within a star. On this way, we recover the Chiral Magnetic Effect (CME) as a possible source for the amplification of a seed, sufficiently strong magnetic field, $B\sim 10^{13}\text{G}$, up to values $B\gtrsim 10^{18}\text{G}$ in old NS's, having ages $t\gtrsim 10^6\text{yr}$. The important issue in AMHD model suggested is the continuous evolution of the chiral imbalance providing the CME for these ages, ${\partial }_t{\mu }_5(t)\ne 0$, in spite of the fast spin-flip in Coulomb collisions in the dense NS plasma that leads to vanishing ${\mu }_5\to 0$ at an earlier epoch in the corresponding protoneutron star. In contrast to the conventional mean-field dynamos, the dynamo drivers in the model are produced due to magnetic field generated at the previous stages of stellar evolution. It makes our model basically nonlinear.

Comments: 14 pages in LaTeX2e, JCAP LaTeX style, 6 eps figures. The paper has been withdrawn since the main results are incorrect. We have partly corrected them in arXiv:2001.08139