Kinetic effect on low frequency Alfvén continuum in tokamaks

Elfimov, A. G.
July 2008
Physics of Plasmas;Jul2008, Vol. 15 Issue 7, p074503
Academic Journal
Using a quasi-toroidal set of coordinates in plasmas with coaxial circular magnetic surfaces, the Vlasov equation is solved, and dielectric tensor is found for large aspect ratio tokamaks in a low frequency band. Taking into account the q-profile and drift effects, Alfvén wave continuum deformation by geodesic effects is analyzed. It is shown that the Alfvén continuum has a minimum defined by the ion thermal velocity at the rational magnetic surfaces qs=-M/N, where M and N are the poloidal and toroidal mode numbers, respectively, and the parallel wave number is zero. Low frequency global Alfvén waves are found below the continuum minimum. In hot ion plasmas, the geodesic term changes sign, provoking some deformation of Alfvén velocity by a factor (1+q2)-1/2, and the continuum minimum disappears.


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