H-mode
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When a magnetically confined plasma is heated strongly, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state. [1] In the H-mode, the energy confinement time is significantly enhanced, i.e., typically by almost a factor of 2.
This transport bifurcation is the consequence of the suppression of turbulence in the edge plasma, associated with a shear flow layer and an associated edge radial electric field. The precise mechanism governing this phenomenon is the subject of ongoing studies.
The steep edge gradients lead to quasi-periodic violent relaxation phenomena, known as Edge Localized Modes (ELMs), which have a strong impact on the surrounding vessel.