Channeling of the energy and momentum during energetic-ion-driven instabilities in fusion plasmas.

New features of instabilities driven by energetic ions are revealed. It is found that these instabilities can affect plasma heating and rotation by channeling the energy and momentum of the energetic ions to the region where the destabilized waves are damped. Because of the energy channeling, the plasma core may not be heated by the energetic ions even when these ions have a very peaked radial distribution. It is likely that this new phenomenon can explain experiments on the spherical torus NSTX where a broadening of the temperature profile and even a drop of the temperature at the plasma center with increasing injected power were observed during Alfvén instabilities [D. Stutman, Phys. Rev. Lett. 102, 115002 (2009)10.1103/PhysRevLett.102.115002]. The momentum channeling can lead to plasma rotation and frequency chirping due to the Doppler shift varying in time.