The dynamics of the core and outer microturbulence during the low-intermediate-high (L-I-H) confinement transition have been investigated simultaneously by a tangential CO 2 laser collective scattering system on EAST. It is found that, the intensity of micro-turbulence decreases most strongly near the outer region of the plasma, with less dramatic reduction deeper into the plasma. During the transition, the cross-coherence between broadband turbulence at neighboring wave-numbers in the same region of the plasma increase from less than 0.3 to greater than 0.8 just after the I-H transition. Besides, the magnetic fluctuations in the LCO frequency range reaches a maximum just before the final transition to H-mode, indicating the plausible underlying role of the perturbation of the pressure gradient in the triggering of the transition dynamics. These results would help to achieve a more comprehensive understanding of the L-H transition mechanism.
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