AMPLIFICATION OF NEUTRON-STAR MAGNETIC-FIELDS BY THERMOELECTRIC EFFECTS .5. INDUCTION OF LARGE-SCALE TOROIDAL FIELDS

The investigation of neutron star magnetic field evolution driven by t hermoelectric effects is continued. As in previous papers the magnetic field is assumed to be created in the liquid layer of the crust of ho t newly born neutron stars. Taking into account the locally very large magnetization of the plasma the model has been extended to be applica ble up to still nonquantizing magnetic field strengths in the order of 10(12)...10(13) G. By use of former analytic investigations, which sh ow that - independently of the seed field symmetry - especially axisym metric 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 ra pidly growing small-scale modes in terms of an averaged axisymmetric r epresentative mode, the coupling to individual large-scale modes is nu merically investigated. Non-linear interactions yield a saturation of the growth of the small-scale field modes at field strengths of about 10(12)...10(13) G after less than 20 years. Simultaneously, toroidal l arge-scale field modes are generated up to rather large field strength s. After an initially very rapid exponential increase their growth slo ws down, they are diffusing inward and their strengths are in the orde r of some 10(11) G after 100...1000 years. This behaviour is rather in dependent of the neutron star model. Therefore, a possible scenario fo r magnetic held evolution in the neutron star crust can be constructed .