Intrinsic Rotation Driven by Non-Maxwellian Equilibria in Tokamak Plasmas

The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising from diamagnetic effects, introduce a strong dependence of the radial flux of cocurrent toroidal angular momentum on collisionality: As the plasma goes from nearly collisionless to weakly collisional, the flux reverses direction from radially inward to outward. This indicates a collisionality-dependent transition from peaked to hollow rotation profiles, consistent with experimental observations of intrinsic rotation.

Figure 1

Ratio of radial fluxes of ion toroidal angular momentum $\Pi$ and energy $Q_i$ vs normalized ion-ion collision frequency ${\nu }_{*}$.

Figure 2

Ratio of radial fluxes of ion toroidal angular momentum $\Pi$ and energy $Q_i$ vs normalized ion-ion collision frequency ${\nu }_{*}$ for: the base simulations (solid black line), simulations with no $E\times B$ rotation to balance the diamagnetic rotation (short dashed blue line), simulations with no correction $F_1$ to the Maxwellian equilibrium (long dashed red line), and simulations with ${\Pi }_{\mathrm{other}}=0$ (dotted green line).

Figure 3

Ratio of radial fluxes of ion toroidal angular momentum ${\Pi }_i$ and energy $Q_i$ vs normalized second derivative of the logarithmic ion temperature for: the base simulations (solid black line) and for simulations with no $E\times B$ flow to balance the diamagnetic flow (short dashed red line) and no correction $F_1$ to the Maxwellian equilibrium (long dashed blue line).