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

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, $Bsim 10^{13},text{G}$, up to values $Bgtrsim 10^{18},text{G}$ in old NSs, having ages $tgtrsim 10^6,text{yr}$. The important issue in AMHD model suggested is the continuous evolution of the chiral imbalance providing the CME for these ages, $partial_tmu_5 (t) eq 0$, in spite of the fast spin-flip in Coulomb collisions in the dense NS plasma that leads to vanishing $mu_5to 0$ 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.