Transient particle acceleration in strongly magnetized neutron stars

Although several reasonable physical processes have been proposed to account for the initial energy release in transient events on strongly magnetized neutron stars, and although the manifestation of this activity as a burst of X- or γ-radiation evidently results from the Compton upscattering of soft photons by relativistic electrons, a self-consistent picture for the particle acceleration itself is lacking. Here, we develop a detailed model in which sheared Alfvén waves generated by the energized stellar crust (e.g., due to a starquake) accelerate the charges to large Lorentz factors. We show that for canonical stellar parameters and a burst energy ∼10³⁷ ergs, the maximum attainable Lorentz factor is γ_max ∼ 50m, where m(∼2-3 cm^-1) characterizes the shear of the magnetic perturbation. This value of γ_max is consistent with the particle energy required to produce the most energetic y-rays (∼10-100 MeV) observed in y-ray bursts.