2017/10/20 by Siyao Xu, Alex Lazarian · 36 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cosmic ray #Dynamo #Ionosphere and magnetosphere dynamics #Magnetic energy #Magnetic field #Shock (circulatory) #Shock wave #Shock waves in astrophysics #Solar and Space Plasma Dynamics #Supernova #Turbulence #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/aa956b
published in The Astrophysical Journal 850(2), 126 (IOP Publishing) · 8 pages, 2 figures, accepted for publication in ApJ
arxiv created 2017/10/20 · openalex created_date 2017/11/10 · openalex publication_date 2017/11/27 · arxiv updated 2017/12/13 · openalex updated_date 2026/08/05
Abstract Based on the new findings on the turbulent dynamo in Xu & Lazarian, we examine the magnetic field amplification in the context of supernova remnants. Due to the strong ion-neutral collisional damping in the weakly ionized interstellar medium, the dynamo in the preshock turbulence remains in the damping kinematic regime, which leads to a linear-in-time growth of the magnetic field strength. The resultant magnetic field structure enables effective diffusion upstream and shock acceleration of cosmic rays to energies above the “knee.” Differently, the nonlinear dynamo in the postshock turbulence leads to a linear-in-time growth of the magnetic energy due to the turbulent magnetic diffusion. Given a weak initial field strength in the postshock region, the magnetic field saturates at a significant distance from the shock front as a result of the inefficiency of the nonlinear dynamo. This result is in a good agreement with existing numerical simulations and well explains the X-ray spots detected far behind the shock front.