Magnetic phase transitions in plasmas and transport barriers

A model of magnetic phase transitions in plasmas is presented: plasma elements with pressure excess or defect are dia- or paramagnets and move radially under the influence of the background plasma magnetization. It is found that magnetic phase separation could be the underlying mechanism of L to H transitions and drive transport barrier formation. Magnetic phase separation and the associated pedestal build-up, as described here, can be explained by the well-known interchange mechanism, now reinterpreted as a magnetization interchange. The interchange mechanism can drive motion of plasma elements even when stable. A testable necessary criterion for the L to H transition is presented. (paper)