ELECTRICAL-CONDUCTIVITY OF NEUTRON-STAR CORES IN THE PRESENCE OF A MAGNETIC-FIELD .2. A FREE-PARTICLE MODEL OF NPE-SIGMA--MATTER

General theory of electrical conductivity of a multicomponent mixture of degenerate fermions in a magnetic field B, developed in the preceding article (this volume), is applied to a matter in neutron star interiors at densities rho greater-than-or-similar-to rho-0, where rho-0 = 2.8 x 10(14) g cm-3 is the standard nuclear matter density. A model of free-particle mixture of n, p, e is used, with account for appearance of SIGMA--hyperons at rho > rho-c, where rho-c almost-equal-to 4-rho-0. The electric resistivities along and across B, R parallel-to and R perpendicular-to, and the Hall resistivity R(H) are calculated and fitted by simple analytical formulae at rho less-than-or-equal-to rho-c and rho > rho-c for the cases of normal or superfluid neutrons provided other particles are normal. Charge transport along B is produced by electrons, due to their Coulombic collisions with other charged particles; R parallel-to is independent of B and almost independent of the neutron superfluidity. Charge transport across B at large B may be essentially determined by other charged particles. If rho less-than-or-equal-to rho-c, one has R perpendicular-to = R parallel-to [1 + (B/B0)2] for the normal neutrons, and R perpendicular-to = R parallel-to for the superfluid neutrons, while R(H) = R parallel-to B/B(e) for both cases. Here B(e) approximately 10(9)T8(2)G, B0 approximately 10(11)T8(2)G, and T8 is temperature in units of 10(8) K. Accordingly for the normal neutrons at B >> B0, the transverse resistivity R perpendicular-to suffers an enhancement, R perpendicular-to >> R parallel-to. When rho greater-than-or-similar-to 5-rho-0 and B varies from 0 to B approximately B(p) proportional 10(13)T8(2)G, R perpendicular-to increases by a factor of about 10(3)-10(4) and R(H) changes sign. When B >> B(p), R perpendicular-to remains constant for the superfluid neutrons, and R perpendicular-to proportional B2 for the normal neutrons, while R(H) proportional B for any neutron state. Strong dependence of resistivity on B, T, and rho may affect evolution of magnetic fields in neutron star cores. In particular, the enhancement of R perpendicular-to at high B may noticeably speed up the Ohmic decay of those electric currents which are perpendicular to B.