(PD/P-04) Statistical Theory of L-H Transition and its Implication to Threshold Data Base

**Abstract.** A statistical model for the bifurcation of the radial electric field E_{r} is analyzed in
view of describing L-H transitions of toroidal plasmas. Noise in micro fluctuations is
shown to lead to random changes of E_{r}, if a deterministic approach allows for more than
one solution. The probability density function for and the ensemble average of Er are
obtained. The L-to-H and the H-to-L transition probabilities are calculated, and the
effective phase limit is derived. Due to the suppression of turbulence by shear in E_{r}, the
limit deviates from Maxwell's rule.

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*IAEA 2003*