Neutrino emissivity from e-e+ annihilation in a strong magnetic field: Hot, nondegenerate plasma

The neutrino emissivity from e-e+ pair annihilation is calculated for a hot, nondegenerate plasma, T much-gt TF (TF is the electron degeneracy temperature), in a magnetic field B of arbitrary strength. The results are fitted by an analytic expression. A not-very-strong magnetic field, b=B/Bc much-lt 1 (Bc=4.41x1013 G), enhances the emissivity of a nonrelativistic plasma, t=T/Tc approx-lt b (Tc=6x109 K), and does not affect the emissivity at higher T. Stronger fields, b much-gt 1, influence the pair annihilation if t approx-lt √b . At t approx-gt b1/4 they suppress the process, and at t much-lt b1/4 they enhance it. As a rule the pair annihilation dominates over other neutrino production mechanisms in a hot plasma of neutron-star envelopes