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Abstract

2-D MHD Configurations for Accretion Disks around Magnetized Stars

The description of an accretion disk around a compact and strongly magnetized star within the framework of two-dimensional local MHD profiles is presented. After a brief review of the crystalline structure the disk acquires because of the coupling of the radial and vertical equilibria (as shown by B. Coppi in 2005), we face the question of making account for a non-zero accretion rate. In particular, the puzzle of a self-consistent configuration, for which the electron force balance holds in the azimuthal direction, is addressed. In the limit of a linearized perturbation theory, the accretion characteristics, as coming out of the two-dimensional MHD, are discussed either in the case of a non-zero Nernst coefficient of the plasma, and when resistivity is involved in the model. In both these cases, we will deal with an oscillating radial matter in-fall. The possible implication of non-linear resistivity features, in view of the growth of plasma instabilities are eventually presented within the ring-morphology preservation. Results and perspectives are given. In particular, we stress that one of us (B.C.) is investigating an accretion scenario involving very low relative values of the plasma resistivity.

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