Abstract
The physics of active galactic nuclei (AGN) and related objects is one of the most actively pursued areas in astrophysics. Their large luminosities over the entire electromagnetic spectrum combined with extremely short-time variability has stimulated a large number of astrophysicists to propose rather unconventional ideas. After a simplistic review of the early work on AGN, a case is made for the important role of some of the nonlinear plasma processes in the generation of the nonthermal continuum as well as its interaction with the plasma surrounding the central source in the form of accretion disks and emission line regions. These plasma processes are fast, as they operate on characteristic time scales much shorter than the single particle processes do. Due to their collective nature. the efficiencies of scattering, absorption and emission increase many fold. In particular, it is shown how the parametric instabilities cause anomalous absorption and scattering and in turn heat the plasma to much higher temperatures than could be achieved through particle collisions. A combination of the stimulated Raman and Compton scattering processes is shown to be able to account for the major part of the spectrum of 3C273, as an example. An attempt is made to address simultaneously the questions of acceleration of particles and their radiation through the concerted action of a sequence of plasma processes. This review ends with some reflections on future research directions.
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Aller, M. F., Aller, H. D., and Hughes, P. A.: 1991, in J. Roland, H. Sol, and G. Pelletier (eds.), Flux And Polarization Variability: Constraints on AGN Modeling, Extragalactic Radio Sources - From Beams to Jets, 7th IAP Meeting, Cambridge University Press, Cambridge, p. 167.
Antonucci, R.: 1993, ‘Unified Models for Active Galactic Nuclei and Quasars’, Ann. Rev. Astron. Astrophys. 31, 473.
Barnothy, J. M.: 1965, ‘Quasars and the Gravitational Image Intensifier’, Astron. J. 70, 666.
Barthel, P. D.: 1992, in W. J. Duschl and S. J. Wagner (eds.), Unified Schemes for Radio-Loud and Radio-Quiet QSO's, Physics of Active Galactic Nuclei, Springer-Verlag, Berlin, p. 637.
Barvainis, R.: 1987, ‘Hot Dust and the Near-Infrared Bump in the Continuum Spectra of Quasars and Active Galactic Nuclei’, Astrophys. J. 320, 537.
Barvainis, R.: 1993, ‘Free Emission and the Big Blue Bump. In Active Galactic Nuclei’, Astrophys. J. 412, 513.
Belkov, S. A. and Tsytovich, V. N.: 1973, ‘Modulatin Excitation of Magnetic Fields’, Soviet Phys. JETP 49(4), 656.
Belkov, S. A. and Tsytovich, V. N.: 1982, ‘Modulation Non-Linear Generation of the Magnetic Fields in Dense Plasma’, Phys. Scripta 25, 416.
Blandford, R. D., Mckee, C. F., and Rees, M. J.: 1977, ‘Super-Luminal Expansion in Extragalactic Radio Sources’, Nature 267, 211.
Blandford, R. D. and Konigl, A.: 1979, ‘Relativistic Jets as Compact Radio Sources’, Astrophys. J. 232, 34.
Blandford, R. D. and Payne, P. G.: 1982, ‘Hydromagnetic Flows from Accretion Discs and the Production of Radio Jet’, Monthly Notices Roy. Astron. Soc. 199, 883.
Bregman, J. N.: 1990, Astron. Astrophys. Rev. 2, 125.
Bregman, J.N.: 1994, in T. J. L. Courvoisier and A. Blecha (eds.), ‘The Origin of Continuum Emission in Active Galactic Nuclei’, IAU Symp. 159, 5.
Chen, F. F.: 1974, Introduction To Plasma Physics, Plenum Press, London.
Colgate, S. A.: 1994, ‘Acceleration in Astrophysics’, Phys. Scripta T52, 96.
Coppi, R., Blandford, R. D., and Rees, M. J.: 1993. ‘Anisotropic Induced Compton Scattering - Constraints on Models of Active Galactic Nuclei’, Monthly Notices Roy. Astron. Soc. 262, 603.
Cotton, W. D. et al.: 1984, ‘VLBI Observations of the Polarized Radio Emission from The Quasar 3C454.3’, Astrophys. J. 286, 503.
Courvoisier, T. J. L. et al.: 1987, ‘The Radio to X-Ray Continuum Emission of the Quasar 3C273 and Its Temporal Variations’, Astron. Astrophys. 176, 209.
Czerny, B.: 1994, in T. J. L. Courvoisier and A. Blecha (eds.), ‘Emission of Accretion Disks’, IAU Symp. 159, 261.
Daltabuit, E. and Cox, D. P.: 1972, ‘K Shell Photoionization Cross-Sections’, Astrophys. J. 177, 855.
Daltabuit, E., MacAlpine, G. M., and Cox, D. P.: 1978, ‘The Structure and Spectrum of a Colliding Cloud System and Its Possible Relationship to QSOs’, Astrophys. J. 219, 372.
Davidson, K.: 1972, ‘Photoionization and the Emission Line Spectra of Quasi-Stellar Objects’, Astrophys. J. 171, 213.
Davidson, K. and Netzer, H.: 1979, ‘The Emission Lines of Quasars and Similar Objects’, Rev. Mod. Phys. 51, 715.
Edelson, R. A. and Malkan, M. A.: 1986, ‘Spectral Energy Distributions of Active Galactic Nuclei Between 0.1 and 100 Microns’, Astrophys. J. 308, 59.
Eilek, J. A. and Caroff, L.J.: 1976, ‘Cloud Acceleration by Cosmic Rays in the Vicinity of Compact Luminous Objects’, Astrophys. J. 208, 887.
Figueroa, H. et al.: 1984, ‘Stimulated Raman Scattering, Two-Plasmon Decay and Hot Electron Generation from Underdense Plasma at 0.35 μm’, Phys. Fluids 27, 1887.
Fried, D. and Conte, S. D.: 1961, ‘The Plasma Dispersion Function’, New York Academic, New York.
Ginzburg, V. L. and Syrovatskii, S. I.: 1969, ‘Developments in the Theory of Synchrotron Radiation and Its Reabsorption’, Ann. Rev. Astron. Astrophys. 7, 375.
Gangadhara, R. T. and Krishan, V.: 1990, ‘Radio Wave Heating of Astrophysical Plasmas’, J. Astrophys. Astron. 11, 515.
Gangadhara, R. T. and Krishan, V.: 1992, ‘The Role of Compton and Raman Scattering in the Quasar Continuum’, Monthly Notices Roy. Astron. Soc. 256, 111.
Gangadhara, R. T. and Krishan, V.: 1993 ‘Polarization Changes of Radiation Through Stimulated Raman Scattering’, Astrophys. J. 415, 505.
Gangadhara, R. T. and Krishan, V.: 1995, ‘Rapid Polarization Variability in Intense Sources’, Astrophys. J. 440, 116.
Gangadhara, R. T., Krishan, V., and Shukla, P. K.: 1993, ‘The Modulation of Radiation in an Electron-Positron Plasma’, Monthly Notices Roy. Astron. Soc. 262, 151.
Harris, E. G.: 1975, ‘Introduction to Modern Theoretical Physics’, Vol. 2, Quantum Theory and Statistical Physics, Wiley-Interscience Publ., New York, p. 735.
Hasegawa, A.: 1978, ‘Free Electron Laser’, Bell System Tech. J. 57, 3069.
Hoyle, F., Burbidge, G. R., and Sargent, W. L.W.: 1966, ‘On the Nature of the Quasi-Stellar Sources’, Nature 209, 751.
Hughes, P. A., Aller, H. D., and Aller, M. F.: 1985, ‘Polarized Radio Outburst in BL LACERTEA II: The Flux And Polarization of A Piston-Driven Shock’, Astrophys. J. 298, 301.
Jones, T. W., O'Dell, S. L., and Stein, W. A.: 1974, ‘Physics of Compact Non-Thermal Sources II: Determination of Physical Parameters’, Astrophys. J. 192, 261.
Kaw, P. K., Schmidt, G., and Wilcox, T.: 1973, ‘Filamentation and Trapping of Electromagnetic Radiation in Plasmas’, Phys. Fluids 16, 1522.
Kniffen, D. A. et al.: ‘Time Variabality in the Gamma-Ray Emission of 3C279’, Astrophys. J. 411, 133.
Kono, M., Skoric, M. M., and ter Haar, D.: 1981, ‘Spontaneous Excitation of Magnetic Fields and Collapse Dynamics in a Langmuir Plasma’, J. Plasma Phys. 26, 123.
Krishan, V.: 1978, ‘Conductivity of an Ion-Acoustically Turbulent Plasma’, Solar Phys. 59, 29.
Krishan, V.: 1983, ‘Emission Mechanism of Extragalactic X-ray and Radio Sources’, Astrophys. Lett. 23, 133.
Krishan, V.: 1985, ‘Acceleration and Radiation Processes Around Active Galactic Nuclei’, Astrophys. Space Sci. 115, 119.
Krishan, V.: 1987, ‘Anomalous Heating of Quasar Emission - Line Regions’, Monthly Notices Roy. Astron. Soc. 226, 629.
Krishan, V.: 1988a, ‘Is 21-cm Absorption Associated with the Emission-Line Regions of Quasars’, Monthly Notices Roy. Astron. Soc. 231, 357.
Krishan, V.: 1988b, ‘Scattering of Quasar Radiation in the Intercloud Medium’, Monthly Notices Roy. Astron. Soc. 234, 79.
Krishan, V.: 1988c, ‘Raman Scattering of the Synchrotron Self-Absorbed Radiation in Accretion Discs’, Monthly Notices Roy. Astron. Soc. 230, 183.
Krishan, V.: 1988d, ‘One More Explanation of Superluminal Motion’, J. Astrophys. Astron. 9, 231.
Krishan, V.: 1993, ‘The Extraterrestrial Raman Scattering’, Current Sci. 64, 301.
Krishan, V.: 1994, ‘Role of Plasma Processes in Astrophysics’, Phys. Scripta T52, 118.
Krishan, V. and Wiita, P. J.: 1990, ‘Coherent Plasma Processes and the Continuum Emission in Active Galactic Nuclei’, Monthly Notices Roy. Astron. Soc. 246, 597.
Krishan, V. and Wiita, P. J.: 1994, ‘Plasma Mechanisms for Variability in Active Galactic Nuclei’, Astrophys. J. 423, 172.
Krolik, J. H., McKee, C. F., and Tarter, C. B.: 1978, in A. Wolfe (ed.), Proc. Pittsburgh Conference on BL Lacertae Objects, University of Pittsburgh, Pittsburgh, p. 277.
Krolik, J. H., McKee, C. F., and Tarter, C. B.: 1981, ‘Quasar Emission Line Regions’, Astrophys. J. 249, 492.
Kruer, L. W.: 1988, The Physics of Laser Plasma Interactions, Addison-Wesley Publ. Co. Inc., New York.
Lesch, H. and Pohl, M.: 1992, ‘A Possible Explanation for Intraday Variability in Active Galactic Nuclei, Magnetic Reconnection And Coherent Plasma Emission’, Astron. Astrophys. 254, 29.
Lesch, H. and Schlickeiser, R.: 1987, ‘Stabilization and Consequences of Relativistic Electron Bumps in Extragalactic Radio Sources’, Astron. Astrophys. 179, 93.
Levich, E. V. and Sunyaev, R. A.: 1971, ‘Heating of Gas near Quasars, Seyfert-Galaxy Nuclei and Pulsars by Low-Frequency Radiation’, Soviet Astron. 15, 363.
Levinson, A. and Blandford, R.: 1995, ‘Raman Scattering in High-Radio-Brightness Astrophysical Systems: Application to Active Galactic Nuclei’, Monthly Notices Roy. Astron. Soc. 274, 717.
Lightman, A. P.: 1982, ‘Relativistic Thermal Plasma: Pair Processes and Equilibria’, Astrophys. J. 253, 849.
Liu, C. S. and Kaw, P.: 1976, ‘Parametric Instabilities in Homogeneous Unmagnetized Plasmas’, Adv. Plasma Phys. 6, 83.
Malkan, M. A.: 1991, in C. Bertout, S. Collin, J. P. Lasota, and J. Tran Thanh Van (eds.), ‘Accretion Disk Models for Active Galactic Nuclei’, Structure and Emission Properties of Accretion Disks, Ed. Frontiers, Gif-sur-Yvette, p. 165.
Malkan, M. A.: 1992, in W. J. Duschl and S. J. Wagner (eds.), ‘Examining Alternatives to Accretion Disk Models for the AGN Continuum’, Physics of Active Galactic Nuclei, Springer-Verlag, Berlin, p. 109.
Mannheim, K.: 1994, T. J. L. Courvoisier and A. Blecha (eds.), On the Difference Between Radio Loud and Radio Quiet AGN, Multiwavelength Continuum Emission of AGN, Kluwer Academic Publishers, Dordrecht, p. 285.
Marscher, A. P. and Bloom, S. D.: 1992, Compton Observatory Science Workshop, p. 346.
McCray, R.: 1979, in C. Hazard and S. Mitton (eds.), ‘Spherical Accretion onto Supermassive Black Holes’, Active Galactic Nuclei, Proceedings of a Nato Study Institute held at the Institute of Astronomy, University of Cambridge, Cambridge, p. 227.
Mathews, W. G. and Captiotti, E. R.: 1985, in J. S. Miller (ed.), ‘Structure and Dynamics of the Broad Line Regions’, Astrophysics of Active Galaxies and Quasi-Stellar Objects, University Science Books, Mill Valley, p. 185.
Miller, H. R. and Wiita, P. J. (eds.): 1991, Variability of Active Galactic Nuclei, Cambrige University Press, Cambridge.
Mushotzky, R. F., Done, C., and Pounds, K. A.: 1993, ‘X-Ray Spectra and Time Variability of Active Galactic Nuclei’, Ann. Rev. Astron. Astrophys. 31, 13.
Novikov, I. and Thorne, K. S.: 1973, in C. Dewitt and B. Dewitt (eds.), ‘Black Hole Astrophysics’ Black Holes, Gordon and Breach, New York, p. 343.
Nussbaumer, H. and Osterbrock, D. E.: 1970, ‘On the Forbidden Emission Lines of Iron in Seyfert Galaxies’, Astrophys. J. 161, 811.
Osterbrock, D. E. and Mathews, W. G.: 1986, ‘X-Ray Spectra and Time Variability of Active Galactic Nuclei’, Ann. Rev. Astron. Astrophys. 31, 717.
Osterbrock, D. E. and Parker, R. A. R.: 1965, ‘Physical Conditions in the Nucleus of the Seyfert Galaxy NGC 1068’, Astrophys. J. 141, 892.
Pacholczyk, A. G.: 1970, Radio Astrophysics, Freeman, San Francisco.
Pacini, F. and Salvati, F.: 1982, in D. S. Heeschen and C. M. Wade (eds.), ‘The Nature of the Energy Source in Radio Galaxies and Active Galactic Nuclei, Extragalactic Radio Sources’, IAU Symp. 97, 247.
Phinney, E. S.: 1985, J. S. Miller (ed.), ‘Central Radio Sources’, Astrophysics of Active Galaxies and Quasi-Stellar Objects, Oxford University Press, Oxford, p. 453.
Rees, M. J.: 1966 ‘Appearance of Relativistically Expanding Radio Sources’, Nature, 211, 468.
Rees, M. J.: 1977, ‘Quasar Theories’, Ann. N.Y. Acad. Sci. 302, 613.
Rees, M. J.: 1984, ‘Black Hole Models for Active Galactic Nuclei’, Ann. Rev. Astron. Astrophys. 22, 471.
Rees, M. J. et al.: 1969, ‘Infrared Radiation from Dust in Seyfert Galaxies’, Nature 223, 788.
Rieke, G. H.: 1978, ‘The Infrared Emission of Seyfert Galaxies’, Astrophys. J. 226, 550.
Robson, E. I. et al.: 1986, ‘A New Infrared Spectral Component of the Quasar 3C273’, Nature 323, 134.
Rybicki, G. B. and Lightman, A. P.: 1979, Radiative Processes in Astrophysics, Wiley-Interscience Publication, New York.
Scheuer, P. A. G.: 1984, in R. Fanti, K. Kellermann and G. Setti (eds.), ‘Explanations of Superluminal Motion’, IAU Symp. 110, 197.
Scheuer, P. A. G.: 1995, ‘Lobe Asymmetry and the Expansion Speeds of Radio Sources’, Monthly Notices Roy. Astron. Soc. 277, 331.
Shields, G. A.: 1978, ‘Thermal Continuum from Accretion Disks in Quasars’, Nature 272, 706.
Sillanpaa, A., Nilsson, K., and Takalo, L. O.: 1991, in J. Roland, H. Sol, and G. Pelletier (eds.),’ Rapid 55 Degree Swing in the Position Angle of the Polarization in OJ 287: A Flare in the Accretion Disk?’, Extragalactic Radio Sources - From Beams to Jets, 7th IAP Meeting, Cambridge University Press, Cambridge, p. 174.
Spangler, S. R.: 1982, in D. S. Heeschen and C. M. Wade (eds.), ‘Spectral Shapes of Compact Extragalactic Radio Sources’, Extragalactic Radio Sources, D. Reidel Publ. Co., Dordrecht, Holland, p. 297.
Stein, W. A. and O'Dell, S. A.: 1985, in J. S. Miller (ed.), ‘The Radio to X-Ray Continuua of AGN’, Astrophysics of Active Galaxies and Quasi-Stellar Objects, Oxford University Press, Oxford, p. 381.
Stockman, H. S.: 1978, in A-.M. Wolfe (ed.), ‘A Report on the Liner Polarization Survey’ Pittsburgh Conference on BL Lac Objects, University of Pittsburgh, Pittsburgh, p. 149.
Svensson, R.: 1982, ‘Electron-Positron Pair Equilibria in Relativistic Plasmas’, Astrophys. J. 258, 335.
Svensson, R.: 1984, ‘Steady Mildly Relativistic Thermal Plasma: Processes and Properties’, Monthly Notices Roy. Astron. Soc. 209, 175.
Tamor, S.: 1973, ‘Effect of Partial Coherence on Laser-Driven Plasma Instabilities’, Phys. Fluids 16, 1169.
Thomson, J. J. et al.: 1974, ‘Parametric Instability Thresholds and Their Control’, Phys. Fluids 17, 849.
Urry, C. M. and Padovani, P.: 1995, Publ. Astron. Soc. Pacific 107, 803.
Valtaoja, E. and Valtonen, M.: 1992, Variability of Blazars, Cambridge University Press, Cambridge.
Weatherall, J. C. and Benford, G.: 1991, ‘Coherent Radiation from Energetic Electron Streams via Collisionless Bremsstrahlung in Strong Plasma Turbulence’, Astrophys. J. 378, 543.
Weymann, R. J., Carswell, R. F., and Smith, M. G.: 1981, ‘Absorption Lines in the Spectra of Quasistellar Objects’, Ann. Rev. Astron. Astrophys. 19, 41.
Wiita, P. J., Kapahi, V. K., and Saikia, D. J.: 1982, ‘Relativistic Beams, Thick Accretion Disks and Active Galactic Nuclei’, Bull. Astron. Soc. India 10, 310.
Wilson, D. B.: 1982, ‘Induced Comption Scattering in Radiative Transfer’, Monthly Notices Roy. Astron. Soc. 200, 881.
Wilson, A. S. and Colbert, E. J. M.: 1995, ‘The Difference Between Radio-Loud and Radio-Quiet Active Galaxies’, Astrophys. J. 438, 62.
Zakharov, V. E.: 1972, ‘Collapse of Langmuir Waves’, Soviet Phys. - JETP 35, 908.
Zdziarski, A. A. et al.: 1990, ‘Electron-Positron Pairs, Compton Reflection and the X-Ray Spectra of Active Galactic Nuclei’, Astrophys. J. 363, L1.
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Krishan, V. Fast Plasma Processes in Active Galactic Nuclei. Space Science Reviews 80, 445–494 (1997). https://doi.org/10.1023/A:1004922327108
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DOI: https://doi.org/10.1023/A:1004922327108