Electron energy losses near pulsar polar caps: a Monte Carlo approach

We use Monte Carlo approach to study the energetics of electrons accelerate d in a pulsar polar gap. As energy-loss mechanisms we consider magnetic Com pton scattering of thermal X-ray photons and curvature radiation. The resul ts are compared with previous calculations which assumed that changes of el ectron energy occurred smoothly according to approximations for the average energy loss rate due to the Compton scattering. We confirm a general dependence of efficiency of electron energy losses due to inverse Compton mechanism on the temperature and size of a thermal pola r cap and on the pulsar magnetic field. However, we show that trajectories of electrons in energy-altitude space as calculated in the smooth way do no t always coincide with averaged Monte Carlo behaviour. In particular, for p ulsars with high magnetic field strength (B-pc greater than or similar to 3 x 10(12) G) and low thermal polar cap temperatures (T less than or equal t o 5 x 10(6) K) final electron Lorentz factors computed with the two methods may differ by a few orders of magnitude. We discuss consequences for parti cular objects with identified thermal X-ray spectral components like Geming a, Vela, and PSR B1055-52.