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arXiv · 0907.4891

Global galactic dynamo driven by cosmic-rays and exploding magnetized stars

Michał Hanasz·Dominik Wóltański·Kacper Kowalik
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Abstract

We report first results of first global galactic-scale CR-MHD simulations of cosmic-ray-driven dynamo. We investigate the dynamics of magnetized interstellar medium (ISM), which is dynamically coupled with the cosmic-ray (CR) gas. We assume that exploding stars deposit small-scale, randomly oriented, dipolar magnetic fields into the differentially rotating ISM, together with a portion of cosmic rays, accelerated in supernova shocks. We conduct numerical simulations with the aid of a new parallel MHD code PIERNIK. We find that the initial magnetization of galactic disks by exploding magnetized stars forms a favourable conditions for the cosmic-ray-driven dynamo. We demonstrate that dipolar magnetic fields supplied on small SN-remnant scales, can be amplified exponentially, by the CR-driven dynamo, to the present equipartition values, and transformed simultaneously to large galactic-scales. The resulting magnetic field structure in an evolved galaxy appears spiral in the face-on view and reveals the so called X-shaped structure in the edge-on view.

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Michał Hanasz, Dominik Wóltański, Kacper Kowalik. 2009-11-05. Global galactic dynamo driven by cosmic-rays and exploding magnetized stars. https://doi.org/10.1088/0004-637x/706/1/l155

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