Turbulence-induced magnetic fields in shock precursors

Galactic cosmic rays are believed to be mostly accelerated at supernova shocks. However, the interstellar magnetic field is too weak to efficiently accelerate galactic cosmic rays up to the highest energies, i.e. \(10^{15}\) eV. A stronger magnetic field in the pre-shock region could provide the eff...

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Bibliographic Details
Published in:arXiv.org 2016-02
Main Authors: del Valle, Maria Victoria, Lazarian, Alexandre, Santos-Lima, Reinaldo
Format: Article
Language:English
Subjects:
Amplification
Computer simulation
Cosmic rays
Galactic cosmic rays
Inhomogeneity
Interstellar magnetic fields
Interstellar matter
Magnetic fields
Magnetism
Precursors
Stability
Turbulence
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Summary:Galactic cosmic rays are believed to be mostly accelerated at supernova shocks. However, the interstellar magnetic field is too weak to efficiently accelerate galactic cosmic rays up to the highest energies, i.e. \(10^{15}\) eV. A stronger magnetic field in the pre-shock region could provide the efficiency required. Bell's cosmic-ray nonresonant streaming instability has been claimed to be responsible for the amplification of precursor magnetic fields. However, an alternative mechanism has been proposed in which the cosmic-ray pressure gradient forms the shock precursor and drives turbulence, amplifying the magnetic field via the small-scale dynamo. A key ingredient for the mechanism to operate are the inhomogeneities present in the interstellar medium (ISM). These inhomogeneities are the consequence of turbulence. In this work we explore the magnetic field amplification in different ISM conditions through 3D MHD numerical simulations.
ISSN:2331-8422
DOI:10.48550/arxiv.1602.03135