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After describing the phenomenology of edge localized modes (ELMs), various theoretical models that have been proposed to explain them are discussed. These fall into three broad classes. Since ELMs are accompanied by bursts of magnetic activity, the first class of models involved the excitation of various magnetohydrodynamic (MHD) instabilities: ideal and resistive ballooning modes, external kink modes and so-called peeling modes. Such models envisage the application of auxiliary heating driving the equilibrium to a state which triggers some such instability, resulting in the loss of plasma, followed by a recovery stage until the cycle is repeated; thus this description of the ELM cycle is merely conceptual. The second class of models involves limit cycle solutions of the transport equations governing the plasma edge region, exploiting the bifurcations inherent in theories of the L-H transition (eg those involving sheared rotation stabilization). In the third class elements of both types of theory have been combined, with MHD or pressure driven fluctuation transport playing a role.

Additional information

Authors: CONNOR J W, AEA Fusion, Culham Laboratory, Abingdon, Oxon (GB)
Bibliographic Reference: Report: EN (1997) 32pp.
Availability: Available from the Librarian, UKAEA, Culham Laboratory, Abingdon, Oxon, OX14 3DB (GB)
Record Number: 199710652 / Last updated on: 1997-06-09
Original language: en
Available languages: en