Abstract.  Internal transport barriers (ITBs) are a key ingredient in advanced tokamak scenarios aiming at steady-state operation and, as presented in the last FPPT (Kathmandu), they sometimes exhibit an oscillatory behavior. In this communication, the interplay between the temperature and the non-inductive current, together with its role on ITB dynamics in tokamak plasmas, is studied. A set of two ordinary differential equations is derived from the reduction of the fluid-like radial energy and current diffusion equations, in which a mixed Bohm-gyroBohm energy diffusivity, dependent on the local magnetic shear, is used. The bifurcation analysis of the resulting dynamical system is attempted.

Depending on the values of a set of relevant parameters, the system’s orbits are shown to possess one of three distinct limit sets: two fixed points, one characteristic of a lowconfinement state and the other characteristic of a high-confinement state, and a limit cycle. These correspond, respectively, to the following experimentally observed states: absence of an ITB, ITB persistence, and ITB repetitive rise and fall in a sequence of oscillations. As a result, threshold conditions for the different regimes are atempted.