Hydromagnetic instabilities in proto-neutron stars

The stability properties of newly born neutron stars, or proto neutron stars (PNSs), are considered. We take into account dissipative processes, such as neutrino transport and viscosity, in the presence of a magnetic field. In order to find the regions of the star subject to different sorts of instability, we derive the general instability criteria and apply them to evolutionary models of PNSs. The influence of the magnetic field on instabilities is analyzed, and the critical magnetic field stabilizing the star is obtained. In light of our results, we estimate the maximum poloidal magnetic field that might be present in young pulsars or magnetars.