DISSIPATION OF MAGNETIC-FIELDS IN ACTIVE GALACTIC NUCLEI

A model for the emission processes causing rapid variability (less tha n one day) in active galactic nuclei is developed. Relativistic electr on beams escape from reconnection sheets in coronae of accretion disks and excite plasma turbulence with a typical frequency omega(pe congru ent-to 5.6 . 10(4) square-root, which depends on the electron number d ensity n (see also the contribution by R. van Oss). The finite lengths of different beams emerging from different reconnection sheets allows that the waves are coherently scattered to frequencies congruent-to g amma2 omega(pe). For Lorentz factors gamma congruent-to 10(3) and dens ities typical for disk coronae n congruent-to 10(6) cm-3 (derived from iron line observations) one easily reaches the optical frequency rang e. The time scale of the variability is then caused by the relaxation of the electron beams. Likewise, this model explains the very rapid va riability in the X-ray (less than 10 minutes) by changing the paramete rs slightly. According to this scenario the higher the variable freque ncy is, the closer to the central black hole it should originate.