Eigenvalue Spectrum of MHD Modes in Cylindrical Tokamak Plasmas with Small Resistivity

For the understandings of the magnetohydrodynamic (MHD) characteristics in plasma, the spectrum of the resistive MHD modes are investigated in detail by solving the eigenvalue problem of the reduced MHD equations in cylindrical tokamak plasmas. The eigenvalues and eigenfunctions of the resistive MHD modes are clarified for small toroidal and poloidal mode numbers, and the discrete eigenvalues with imaginary part are categorized into several types by analyzing the behavior of their eigenfuctions. In particular, the dependence of the eigenvalue distribution in the real-imaginary space on the resistivity is studied for small resistivity regime by parallel computation. It is found that the characteristics of eigenvalue distribution and eigenfunction are changed even for small reduction of resistivity in small resistivity region. It is also found that the distribution structure of the eigenvalues is deformed with bifurcation of spectral curve.