Plasma Current Effects on Unstable Resistive Drift-Alfvén Modes in a Magnetized Cylindrical Plasma

Abstract

In a currentless plasma, there are many unstable drift-Alfven modes with different radial eigenfunctions with fixed poloidal and toroidal mode numbers, m and n , respectively. When growth rates of unstable modes are plotted as a function of total plasma current I p , two opposite tendencies, stabilization and destabilization, are seen with the increase of I p . When two eigenvalues (ω r j ,ω i j ) and (ω r j +1 ,ω i j +1 ), where j denotes the order of the eigenvalue from the largest one, for given m and n become close at I p ≃ I c in a large current regime, the real frequencies do not cross. However, sometimes the two growth rates cross or ω i j =ω i j +1 occurs, although the real frequencies satisfy ω r j >ω r j +1 . The eigenfunctions of the resistive drift-Alfven mode with (ω r j ,ω i j ) at I p ≤ I c are similar to those with (ω r j +1 ,ω i j +1 ) at I p ≥ I c , where ω r j >ω r j +1 . These unstable modes may affect the magnetic spectrum of the drift-Alfven frequency range.