Helicity conservation and dynamo in helical plasma states.

Plasma states dominated by single helical modes are often observed in the Reverse Field Pinch (RFP) magnetic plasma confinement devices. In this presentation the properties of these states are studied assuming the existence of two helicity invariants and of a dynamo electric field directly related to one of them. The steady-state properties of the plasma equilibrium and some interesting physical quantities are derived. Considering the dynamical properties of the transport of helicity from the mesoscale to the macroscale through the dynamo field, a nonlinear dynamical model is also constructed which is able to reproduce a quasi-periodical behavior in time as it is often observed in experiments.