Does the ion diamagnetic drift exist

The behaviour of magnetised plasmas has been analyzed by means of PIC (particle-incell) simulations. It turned out that the dimensionless parameter ξ = (nplM)/(εoB2) defines the role of the magnetic field B (npl is the plasma density and M is the mass of the plasma ions). Under the condition of today's fusion experiments the electrons are usually tied to the magnetic field lines due to their small gyration radii which are comparable to the Debye length. The ions, on the other hand, have much larger gyration radii and the corresponding parameter ξ is about 1000. For such high values of ξ the effect of the magnetic field is so weak, that only electric forces are of importance. In case of a density gradient the difference in the gyration radii of electrons and ions lead to a small charge imbalance sufficient to build up an electric field, which confines the ions. The ion trajectories are transformed in these electric and magnetic fields and the simple model of gyration overlapping used to explain the diamagnetic drift is no longer valid. Resulting implications concerning the ideal MHD theory are discussed. (orig.)