anomalous transport is the loss of heat and particles from a magnetically confined plasma in excess of what collisions can account for — the transport driven by fine-scale plasma turbulence.
The word "anomalous" is a fossil of ignorance. Early tokamak experiments measured heat leaking out tens of times faster than collisional theory predicted, and the unexplained excess was labeled anomalous against the collisional baseline of 📝neoclassical transport. The anomaly has since been explained: gradient-driven microinstabilities — ion temperature gradient modes, trapped electron modes, electron temperature gradient modes — sustain a sea of fine-scale turbulence in any heated 📝plasma, and the resulting eddies convect heat and particles across the magnetic field. Many physicists now simply say turbulent transport.
Anomalous transport is the tax every magnetic confinement device pays and the central quantity of confinement physics: it is what empirical scaling laws parameterize, what gyrokinetic simulation computes from first principles, and what a 📝transport barrier locally switches off. Electron heat transport is almost always anomalous; ion heat transport can approach the neoclassical floor in quiet regimes. Beating this transport down — by machine size, magnetic field, or suppression — is, in large part, what designing a 📝Tokamak means.