Radiation of Relativistic Particles in a Quasi-Homogeneous Magnetic   Field
  Spectrum of radiation of a relativistic particle moving in a nonhomogeneous magnetic field is considered. The spectrum depends on the pitch-angle $\alpha$ between the velocity direction and a line tangent to the field line. In case of very small $\alpha$ the particle generates so-called curvature radiation, in an intermediate case undulator-kind radiation is produced. In this paper we present the calculations of radiation properties in a case when both curvature and undulator radiation is observed. 
V. Epp and T.G. Mitrofanova
astro-ph.HE physics.plasm-ph