  A geometrical correction to the E x B drift causes an outward flux of
cocurrent momentum whenever electrostatic potential energy is transferred to
ion parallel flows. The robust symmetry breaking follows from the free energy
flow in phase space and does not depend on any assumed linear eigenmode
structure, acting both for axisymmetric fluctuations (such as geodesic acoustic
modes) as well as more general nonaxisymmetric fluctuations. The resulting
rotation peaking is countercurrent and scales as electron temperature over
plasma current. This peaking mechanism can only act when fluctuations are
low-frequency enough to excite ion parallel flows, which may explain some
recent experimental observations related to rotation reversals.
