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.

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 The paper has been withdrawn since the main results are incorrect.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