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A new formalism for analysing the magneto-hydrodynamic stability of a limiter tokamak edge plasma is developed. Two radially localized, high toroidal mode number n instabilities are studied in detail: the peeling mode and the ballooning mode. The peeling mode, driven by edge current density and stabilized by edge pressure gradient, has features which are consistent with several properties of tokamak stability in H-mode, and edge localized modes (ELM) in particular. An edge ballooning mode, driven by the pressure gradient, is identified which penetrates approximately n{1/3} rational surfaces into the plasma (rather than approximately n{1/2), expected from conventional ballooning mode theory). Furthermore, there exists a coupling between these two modes and this coupling provides a picture of the ELM cycle.

Additional information

Authors: CONNOR J W, AEA Fusion, Culham Laboratory, Abingdon, Oxon (GB);HASTIE R J, AEA Fusion, Culham Laboratory, Abingdon, Oxon (GB);WILSON H R, AEA Fusion, Culham Laboratory, Abingdon, Oxon (GB)
Bibliographic Reference: Report: UKAEA FUS 383 EN (1997) 32pp.
Availability: Available from the Librarian, UKAEA, Culham Laboratory, Abingdon, Oxon, OX14 3DB (GB)
Record Number: 199810021 / Last updated on: 1998-02-03
Original language: en
Available languages: en