PACS 52.35.Fp-Electrostatic waves and oscillations (e.g., ion-acoustic waves) PACS 52.35.Mw-Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.

We discuss the processes underlying the excitation of fishbone-like internal kink instabilities driven by supra-thermal electrons generated experimentally by different means: Electron Cyclotron Resonance Heating (ECRH) and by Lower Hybrid (LH) power injection. The peculiarity and interest of exciting these electron fishbones by ECRH only or by LH only is also analyzed. Not only the mode stability is explained, but also the transition between steady state nonlinear oscillations to bursting (almost regular) pulsations, as observed in FTU, is interpreted in terms of the LH power input. These results are directly relevant to the investigation of trapped alpha particle interactions with low-frequency MHD modes in burning plasmas: in fact, alpha particles in reactor relevant conditions are characterized by small dimensionless orbits, similarly to electrons; the trapped particle bounce averaged dynamics, meanwhile, depends on energy and not mass.

We present an overview on one issue of practical interest for burning plasmas, i.e. whether fast ions and charged fusion products are sufficiently well confined such that they transfer their energy and/or momentum to the thermal plasma without appreciable degradation due to collective modes. In the present work, we address this issue by analysing theoretically the dynamics of shear Alfvén waves collectively excited by energetic particles in tokamak plasmas. Both linear physics, such as spectral and stability properties, and key non-linear wave and particle dynamics are identified and considered. We also discuss the investigations of such processes via computer simulations as well as the importance of benchmarking with existing or future experimental observations.