A disappearing feast: Mean flows remain slim after eating eddies

Magnetic confinement fusion holds the promise of almost limitless amounts of energy, available on demand and producing zero carbon dioxide. But in order to harness that energy, we must trap plasma—an ionized gas—hotter than the center of the sun inside a donut-shaped magnetic facility called a tokamak that measures just a few yards across. As you might guess, the confined plasma becomes turbulent, and that turbulence leaks energy out from the ultra-hot core to the room-temperature wa