Michał Hanasz et al 2009 ApJ 706 L155 doi:10.1088/0004-637X/706/1/L155
Michał Hanasz, Dominik Wóltański and Kacper Kowalik
Show affiliationsWe report the first results of the first global galactic-scale cosmic ray (CR)-MHD simulations of CR-driven dynamo. We investigate the dynamics of magnetized interstellar medium (ISM), which is dynamically coupled with 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 CRs, 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 favorable conditions for the CR-driven dynamo. We demonstrate that dipolar magnetic fields supplied on small supernova 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.
cosmic rays; galaxies: ISM; galaxies: magnetic fields; ISM: magnetic fields; MHD
95.75.-z Observation and data reduction techniques; computer modeling and simulation
98.35.Hj Spiral arms and galactic disk
98.70.Sa Cosmic rays (including sources, origin, acceleration, and interactions)
98.35.Ac Origin, formation, evolution, age, and star formation
Issue 1 (2009 November 20)
Received 2009 July 2, accepted for publication 2009 October 19
Published 2009 November 4
Michał Hanasz et al 2009 ApJ 706 L155
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