1995A&A...300..429G

The investigation of neutron star magnetic field evolution driven by thermoelectric effects is continued. As in previous papers the magnetic field is assumed to be created in the liquid layer of the crust of hot newly born neutron stars. Taking into account the locally very large magnetization of the plasma the model has been extended to be applicable up to still non-quantizing magnetic field strengths in the order of 10¹²...10¹³G. By use of former analytic investigations, which show that - independently of the seed field symmetry - especially axisymmetric toroidal large-scale modes with even multipolarity are strongly induced, non-linear calculations including these modes are performed. Applying the channel concept, which describes the evolution of the rapidly growing small-scale modes in terms of an averaged axisymmetric representative mode, the coupling to individual large-scale modes is numerically investigated. Non-linear interactions yield a saturation of the growth of the small-scale field modes at field strengths of about 10¹²...10¹³G after less than 20 years. Simultaneously, toroidal large-scale field modes are generated up to rather large field strengths. After an initially very rapid exponential increase their growth slows down, they are diffusing inward and their strengths are in the order of some 10¹¹G after 100...1000 years. This behaviour is rather independent of the neutron star model. Therefore, a possible scenario for magnetic field evolution in the neutron star crust can be constructed.