General radiation formulae for a relativistic charged particle moving in curved magnetic field lines: The synchrocurvature radiation mechanism

We calculate the radiation spectrum, characteristic frequency, and power emitted by a relativistic charged particle moving in curved magnetic field lines with arbitrary pitch angle, which can be approximated by a curved spiral trajectory. We obtain some universal formulae which can be identical to either synchrotron radiation or curvature radiation in certain parametric regions, but in general the radiation features of this new mechanism can significantly differ from those of these two known mechanisms. Since magnetic field lines are generally curved in many real systems (e.g., a pulsar magnetosphere), this new mechanism can more realistically describe the radiation from relativistic charged particles in these systems. We also find that the degree of polarization is the best quantity to differentiate this new mechanism from the other two mechanisms.