Intrinsic rotation drive by collisionless trapped electron mode turbulence

TL;DR

This paper analytically investigates how collisionless trapped electron mode turbulence influences intrinsic plasma rotation, revealing residual stress effects and contrasting turbulent acceleration with ion temperature gradient turbulence.

Contribution

It provides the first analytical calculation of residual stress and turbulent acceleration driven by CTEM turbulence using gyrokinetic theory, highlighting their roles in plasma rotation.

Findings

Residual stress causes outward co-current flux under certain conditions.

Turbulent acceleration driven by CTEM turbulence vanishes due to phase relationships.

Results differ from ion temperature gradient turbulence, affecting rotation drive understanding.

Abstract

Both the parallel residual stress and parallel turbulent acceleration driven by electrostatic collisionsless trapped electron mode (CTEM) turbulence are calculated analytically using gyrokinetic theory. Quasilinear results show that the parallel residual stress contributes an outward flux of co-current rotation for normal magnetic shear and turbulence intensity profile increasing outward. This may induce intrinsic counter-current rotation or flattening of the co-current rotation profile. The parallel turbulent acceleration driven by CTEM turbulence vanishes, due to the absence of a phase shift between density fluctuation and ion pressure fluctuation. This is different from the case of ion temperature gradient (ITG) turbulence, for which the turbulent acceleration can provide co-current drive for normal magnetic shear and turbulence intensity profile increasing outward. Its order of magnitude is predicted to be the same as that of the divergence of the residual stress [Lu Wang and P.H. Diamond, Phys. Rev. Lett. {\bf 110}, 265006 (2013)]. A possible connection of these theoretical results to experimental observations of electron cyclotron heating effects on toroidal rotation is discussed.