Effects of Plasma Diamagnetic Drift on Alfvén Continua and Discrete Eigenmodes in Tokamaks

Alfven continua and Alfven eigenmodes (AEs) in DIII-D plasmas (shot #142111) have been studied using a drift-MHD model with self-consistent plasma diamagnetic drift effects. It is shown that the $$\omega _*$$ causes the frequency upshift in ion diamagnetic drift direction for both Alfven continua and AEs and thus breaks the ion-electron symmetry of the ideal-MHD model results. The BAE gaps are more sensitive to the $$\omega _*$$ modification compared to the TAE gaps located in a higher frequency range. After comparing with self-consistent results, an approximate solution of Alfven continua with $$\omega _*$$ effect is given with high accuracy. The eigenmode structure of TAE is less influenced by $$\omega _*$$ effect compared to the real frequency. The incorporation of the diamagnetic drift effects of the background plasmas and energetic particles (EPs) is important to validate theoretical and simulation models against experiments, i.e., correctly address the continuum and radiative dampings as well as AE resonance condition with EPs.