A new mechanism for pulsar gamma-ray emission

Gamma-ray emission in pulsar magnetospheres is attributed to synchrotron ra diation, which tends to decrease the pitch angle of the particle, being bal anced by plasma processes tending to increase the pitch angle. The plasma p rocesses are non-resonant instabilities that drive non-resonant quasilinear diffusion (NQD), thereby pumping energy from waves and the parallel motion of the particle into the perpendicular motion of the particle. It is shown that NQD can maintain the pitch angles for particles near the light-cylind er such that they radiate synchrotron radiation at MeV energies. Compared t o conventional emission mechanisms (such as polar cap or outer gap models), the resulting spectrum has a relatively low upper cut-off from about a few to 100 MeV. Possible observational consequences of this mechanism are disc ussed.