Model of a giant ELM

A model of the giant ELMs (type-I ELM) is developed. Theory of the self-sustained turbulence of the current-diffusive ballooning mode (CDBM) is developed, and multifold states for the L-mode, H-mode and the third state with magnetic braiding, M-mode, are obtained. The transition to M-mode occurs if the pressure gradient reaches a critical value. The nonlinear excitation of the magnetic perturbation takes place, the growth time of which is of the order of the poloidal-Alfvén transit time, followed by catastrophic enhancement of the transport coefficient. Avalanche of the transport catastrophe is also analysed, showing a very rapid radial propagation velocity. The M-state terminates if the pressure gradient becomes small, leading to the back-transition to the H-(L-)mode. Under the constant power supply, these processes can repeat themselves, causing periodic bursts. The period becomes shorter as the average power flux increases.