When good turns bad: the gyrokinetic field invariant and good-curvature instabilities in fusion plasmas  Speaker Name: Plamen Ivanov, EPFL Lausanne
In this talk, we discuss curvature-driven modes in fusion plasmas and demonstrate that their instability is linked to the conservation law of the so-called gyrokinetic field  invariant. The evolution equation of this invariant, whose electrostatic version is well known, implies that electrostatic modes that are driven unstable by the local magnetic curvature, are bound to reside in the regions of bad curvature. More importantly, we deduce that any mode that is driven unstable in good, rather than bad, curvature must be electromagnetic in nature. As an example, we investigate the properties of a novel good-curvature instability and contrast its properties with the well-known electron-temperature-gradient instability. |