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Astron. Astrophys. 337, 962-965 (1998)

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On the role of self-organised criticality in accretion systems

R.O. Dendy 1, P. Helander 1 and M. Tagger 2

1 UKAEA Fusion, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK
2 DAPNIA/Service d'Astrophysique (CNRS URA 2052), CEA Saclay, F-91191 Gif-sur-Yvette, France

Received 11 December 1997 / Accepted 28 April 1998


Self-organised criticality (SOC) has been suggested as a potentially powerful unifying paradigm for interpreting the structure of, and signals from, accretion systems. After reviewing the most promising sites where SOC might be observable, we consider the theoretical arguments for supposing that SOC can occur in accretion discs. Perhaps the most rigorous evidence is provided by numerical modelling of energy dissipation due to magnetohydrodynamic turbulence in accretion discs by G Geertsema & A Achterberg (A&A 255, 427 (1992)); we investigate how "sandpile"-type dynamics arise in this model. It is concluded that the potential sites for SOC in accretion systems are numerous and observationally accessible, and that theoretical support for the possible occurrence of SOC can be derived from first principles.

Key words: accretion, accretion discs – stars: novae, cataclysmic variables – galaxies: active – X-rays: stars

Send offprint requests to: R.O. Dendy

© European Southern Observatory (ESO) 1998

Online publication: August 27, 1998