The dynamical interplay between turbulent transport, density gradients and radial electric fields has been investigated in the plasma boundary of magnetic confined plasmas. Experimental results show that there is a dynamical relationship between gradients and turbulent transport. Fluctuations on gradients, which turns out to have a rather Gaussian probability density function (PDF), and turbulent transport, which has a non-Gaussian PDF, are strongly coupled. Also, the size of turbulent events increases when the plasma deviates from the average gradient. This increase is particularly significant when the gradient increases above its average value. The system relaxes to the most probable state in a time comparable to the correlation time of turbulence. The present results emphasize the importance of the characterization of fluctuations in the terms of PDFs to test critically edge turbulence models.
An experimentally constrained MHD model for a collisional, rotating plasma column