CYCLO-SYNCHROTRON EMISSION FROM MAGNETICALLY DOMINATED ACTIVE REGIONSABOVE ACCRETION DISCS

We discuss the role of thermal cyclo-synchrotron emission in a magneti cally dominated corona above an accretion disc in an active galaxy or a Galactic black hole candidate. The dissipation occurs in localized a ctive regions around the central black hole. Cyclo-synchrotron radiati on is found to be an important process. In the case of Galactic black hole candidates, its emission can dominate the inverse Compton scatter ing of the soft photon field produced in the disc by thermal electrons . We discuss observational predictions and the detectability of cyclo- synchrotron radiation both for these sources and for radio-quiet activ e galactic nuclei.