  Direct evidence of micro-turbulence effect on the onset of neoclassical
tearing mode (NTM) is reported for the first time in this letter. A puzzling
positive correlation between critical width of seed island of NTM and
normalized plasma pressure beta_p is first observed employing a novel method
for clearly separating the processes of seed island and the onset of NTM in the
EAST tokamak. Different from the methods developed before, the width of the
seed island is well controlled by slowly ramping up the current in resonant
magnetic perturbation coils. It is revealed that the positive correlation is
mainly attributed to the enhancement of perpendicular transport by
micro-turbulence, which overcomes the destabilizing effect of beta_p on the
onset of NTM. Reduced magnetohydrodynamics (MHD) modeling well reproduced the
two states of nonlinear bifurcations observed in this experiment by including
the finite transport effect. This result provides a new route for understanding
multi-scale interaction in plasma physics.
