Alternative Paradigm to Resistive Accretion Disks: Magnetic Microstructures. (arXiv:2009.07215v1 [astro-ph.SR])

Alternative Paradigm to Resistive Accretion Disks: Magnetic Microstructures. (arXiv:2009.07215v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Montani_G/0/1/0/all/0/1">Giovanni Montani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carlevaro_N/0/1/0/all/0/1">Nakia Carlevaro</a>

We analyze the stationary configuration of a thin axisymmetric stellar
accretion disk, neglecting non-linear terms in the plasma poloidal velocity
components. We set up the Grad-Shafranov equation for the system, including the
plasma differential rotation. Then, we study the small scale backreaction of
the disk to the central body magnetic field and we calculate the resulting
radial infalling velocity. We show that the small scale radial oscillation of
the perturbed magnetic surface is associated to the emergence of relevant
toroidal current densities, able to balance the generalized Ohm law even in the
presence of quasi-ideal values of the plasma resistivity. We provide a possible
explanation for the puzzle of an anomalous resistivity, since the Ohm law
involves relevant values of the poloidal velocity which is averaged to zero on
the radial profile of the disk due to the microscopic rapid oscillations. The
contribution to the infalling velocity of the averaged backreaction contrasts
accretion, but it remains negligible as far as the induced magnetic field is
small compared to that of the central body.

We analyze the stationary configuration of a thin axisymmetric stellar
accretion disk, neglecting non-linear terms in the plasma poloidal velocity
components. We set up the Grad-Shafranov equation for the system, including the
plasma differential rotation. Then, we study the small scale backreaction of
the disk to the central body magnetic field and we calculate the resulting
radial infalling velocity. We show that the small scale radial oscillation of
the perturbed magnetic surface is associated to the emergence of relevant
toroidal current densities, able to balance the generalized Ohm law even in the
presence of quasi-ideal values of the plasma resistivity. We provide a possible
explanation for the puzzle of an anomalous resistivity, since the Ohm law
involves relevant values of the poloidal velocity which is averaged to zero on
the radial profile of the disk due to the microscopic rapid oscillations. The
contribution to the infalling velocity of the averaged backreaction contrasts
accretion, but it remains negligible as far as the induced magnetic field is
small compared to that of the central body.

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