Larger and more heterogeneous neutron star crusts: A result of strong magnetic fields

We study the effect of strong magnetic fields, of the order of ${10}^{15}–{10}^{17}$ G, on the extension of the crust of magnetized neutron stars. The dynamical instability region of neutron-proton-electron $\left(npe\right)$ matter at subsaturation densities and the mode with the largest growth rate are determined within a relativistic mean-field model. It is shown that the effect of a strong magnetic field on the instability region is very sensitive to the density dependence of the symmetry energy, and that it is at the origin of an increase of the extension of the crust and of the charge content of clusters.

Figure 1

Dynamical spinodals for the NL3 parametrization, for different magnetic-field intensities and momentum transfer $k=50$ MeV.

Figure 2

Largest growth rate $\mathrm{\Gamma }=\left|\omega \right|$ (top panels), the corresponding half-wavelength (middle panels), and the proton-neutron density fluctuation ratio (bottom panels) versus density, for different magnetic-field intensities and matter with $y_p=0.02$ for NL3 and $y_p=0.035$ for $\mathrm{NL}3\omega \rho$. The black curve corresponds to the $B=0$ results.