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The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential and electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals expressed in terms of the profiles of density etc, which drive the Onsager relaxation of the profiles. Onsager relaxations are possible in the presence of a turbulent field, either in an integrable situation (eg well separated magnetic islands) or in a non-integrable case (overlapping islands). The variational principle then involves the characteristic frequencies of the turbulent field, on the same grounds as the profiles of density, etc.

Additional information

Authors: SAMAIN A, CEA, CEN Cadarache, Saint-Paul-lez-Durance (FR);NGUYEN F, CEA, CEN Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Article: Plasma Physics and Controlled Fusion, Vol. 39 (1997), pp. 1197-1243
Record Number: 199711338 / Last updated on: 1997-10-16
Original language: en
Available languages: en