Spectrum of resistive MHD modes in cylindrical tokamak plasma

Matsumoto, Taro; Tokuda, Shinji

no journal, , 

For the understandings of the tokamak plasma dynamics, the resistive magnetohydrodynamic (MHD) spectrum is investigated in detail by solving the eigenvalue problem of the reduced MHD equations in cylindrical tokamak plasmas. In the presence of the resistivity, the eigenvalues of linearlized resistive MHD are not necessarily purely real, but have imaginary part. Thus, the eigenvalues are distributed on the negative real axis as continuum spectrum of dumping modes, in the complex plane as discrete spectrum of oscillatory and dumping modes, and on the positive real axis as discrete spectrum of unstable mode. For a wide regime of the resistivity from 110 to 1.510, the eigenvalue distribution for m/n=1/1 modes is almost independent of the resistivity, although the density of the eigenvalues on these curves increases. However, for further small resistivity, it is found that the characteristics of eigenvalue distribution and eigenfunction is changed even for small reduction of resistivity.