Intrinsic toroidal rotation of ITER plasmas without external torque
In plain words
Tokamak plasmas spin around the doughnut by themselves even when nothing pushes them, because turbulence moves momentum. ITER will have little external push, and its spin matters for suppressing instabilities, but the self-generated spin cannot be predicted.
Precise statement
Intrinsic rotation arises from residual turbulent momentum stress (symmetry breaking by E x B shear, profile curvature, up-down asymmetry) and edge sources; an empirical multi-machine scaling (Rice and collaborators) relates the core Alfven Mach number to normalized stored energy, and core rotation reverses direction at the transition between linear and saturated Ohmic confinement. Predict the core rotation profile of the ITER $Q = 10$ baseline to within a factor of 2 from a first-principles momentum-transport model, and explain the rotation reversals. An answer is a validated model reproducing intrinsic rotation profiles and reversals on at least two devices.
What would settle it
Gyrokinetic momentum-transport predictions matching measured intrinsic rotation profiles and reversals on two devices, then ITER low-torque H-mode data.