The front propagation of the plasma turbulence in the range of drift wave frequency, which is driven by subcritical excitation mechanism, is investigated. The model of nonlinear instability by phase-space structures is employed. It is found that the turbulence front can propagate ballistically, without being accompanied by the change of mean temperature profile, into the linearly-stable zone of plasmas. The front velocity can be of the order of diamagnetic drift velocity and depends strongly on the isotropy of fluctuations. An implication is made on studies of transport hysteresis, where the rapid jump of fluctuation intensity precedes the gradual change of temperature profile.
Itoh et al. (Mon,) studied this question.