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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. These profiles enter in two functionals reflecting respectively the entropy of the field plasma-plasma system and the entropy production rate. These functionals are symmetrical. By themselves, they would drive an Onsager evolution of the system. However the variational principle contains also an asymmetrical functional reflecting the trajectory effects. The latter is eliminated, so that the Onsager relaxation is automatically established in the situations of low collisionality where the trajectories are integrable and close to the magnetic surfaces. New minimization procedures are proposed to obtain entropy and entropy production rate functionals expressed in terms of the profiles of density and so on which drive the Onsager relaxation of the profiles.

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: Report: EUR-CEA-FC-1592 EN (1997) 62pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez Durance (FR)
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