Giovanni Montani, Daniela Pugliese
We analyze a linear perturbation scheme for a two-dimensional background plasma, which is rotating with a differential frequency and is embedded in a poloidal magnetic field. The plasma profile is axially symmetric, both in the background and the perturbation approximation and the azimuthal magnetic field is requested to vanish identically. The main assumption of the present study is that in the non-stationary regime still holds the dependence of the angular frequency on the magnetic surface function only, which, on the steady background equilibrium, is ensured by the validity of the co-rotation theorem (Ferraro 1937). Indeed, such a restriction of the model is rather natural and it implies that the azimuthal component of the linear plasma shift is reabsorbed in the expression for the non stationary electric field (in principle, at any order of approximation) and can no longer provide a non-zero azimuthal component of the magnetic tension field. As a result, the Magneto-rotational instability is suppressed and the magnetic field has the effect to stabilize the plasma configuration with respect to the pure hydrodynamical case.
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http://arxiv.org/abs/1305.1186
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