REFLECTION OF RADIO RADIATION AT IONIZATION FRONTS IN EMISSION-LINE REGIONS AND ACCRETION DISKS OF ACTIVE GALACTIC NUCLEI

It is known that high frequency short duration electromagnetic pulses can be generated by reflection of low frequency radiation off relativi stically moving ionization fronts. In addition, a part of the incident electromagnetic energy is converted into a spatially periodic static magnetic field. Here, we investigate this phenomenon in the emission l ine region (ELR) and accretion disks of active galactic nuclei (AGN) w here relativistically moving ionization fronts are created by the ioni zing continuum. It is suggested that this process may play an essentia l role in (1) causing rapid correlated variability in radio radiation and high frequency parts of the nonthermal spectrum; (2) generating hi gh frequency radiation through scattering of relativistic electrons of f the spatially periodic magnetic field, a byproduct of the reflection process; (3) the diagnostic of the emission line region; and (4) abso rption of the radio radiation. The anomalous absorption of radio radia tion in ELR through parametric decay instabilities has been pointed ou t earlier. Interaction of radio radiation with ionization fronts furth er strengthens the case for the existence of strong correlation betwee n the nonthermal radio continuum and the ELR phenomena as the multiwav elength observations of AGN are beginning to do.