plasma rotation is the bulk spinning of a magnetically confined plasma around its torus, a motion that suppresses turbulence and stabilizes several of the instabilities that limit tokamak performance.
Rotation is not incidental drift but organized flow: the entire 📝plasma can circulate the long way around a 📝Tokamak at tens or hundreds of kilometers per second. The most common driver is neutral beam injection, whose fast particles deliver torque along with heat, but plasmas also develop intrinsic rotation — spontaneous spin-up with no applied torque, an actively studied effect. Rotation earns its place in the stability lexicon through two services. First, sheared rotation — adjacent layers moving at different speeds — tears turbulent eddies apart before they can carry heat outward, one of the mechanisms behind the edge 📝transport barrier of 📝H-mode. Second, fast rotation keeps instabilities like the 📝tearing mode moving with the plasma: a rotating mode induces stabilizing eddy currents in the vessel wall, while a mode that brakes to a standstill has locked — and a locked mode is a standard prelude to 📝disruption.
The distinction that matters for reactors is between driven and intrinsic rotation. Beam torque per particle shrinks as machines grow larger and denser, so reactor-scale plasmas will rotate far more slowly than today's beam-driven experiments — making the physics of intrinsic rotation, and stability without fast rotation, a live research front.