Cyclo-Synchrotron Radiation at Small Angels.

Cyclo-synchrotron emission at small angles 0 to the magnetic field has a spectral form in frequency quite different from the usual synchrotron spectrum. In particular, the frequency spectrum at 0 = 0 has a spectral index equal to the energy index of the radiating particles for frequencies above i where B = eB/mc is the gyrofrequency and is the minimum energy of the particles. Particles confined to a nauow range of very small pitch angles have a similar spectral index. Thus care must be taken in interpreting the spectral index of sources with special geometries.