THE HYPOTHESIS THAT MAGNETIC-FIELDS BUOYANTLY CONVECT IN NEUTRON-STARS

The hypothesis that a magnetic field convects out of the superconducting interior of a neutron star on a time-scale 10(6)-10(7) yr because of the buoyancy of its individual quantized magnetic flux tubes is critically examined. The hypothesis in its current form equates the buoyancy force of a magnetic flux tube to the viscous force produced by electrons scattering elastically off the flux tube. Examination of the relevant processes with emphasis on the gravity-induced electric field shows that: (i) the picture of flux tubes as independent buoyant entities is invalid in a neutron star because the electron mean free path greatly exceeds the lattice spacing of the flux tubes and the magnetic field is frozen in the electron gas; (ii) the gravity-induced electric field ties the electron and proton gases together and, therefore, the magnetic field is frozen in a quasi-neutral plasma; (iii) the buoyancy of the magnetic flux tubes is already included in the hydrostatic equation and does not require special treatment; (iv) the Lorentz retarding force acting on the lattice owing to its drift motion through the plasma greatly exceeds the viscous force due to electron scatter; and (v) the diffusion time-scale of the magnetic field is of order 10(18) yr, in approximate agreement with original estimates.