scholarly journals Small-scale anisotropies of cosmic rays from relative diffusion

2016 ◽  
Author(s):  
Philipp Mertsch ◽  
Markus Ahlers
Keyword(s):  
Cosmic Rays ◽  
Small Scale ◽  
Relative Diffusion

scholarly journals SMALL-SCALE ANISOTROPIES OF COSMIC RAYS FROM RELATIVE DIFFUSION

2015 ◽  
Vol 815 (1) ◽  
pp. L2 ◽  
Author(s):  
Markus Ahlers ◽  
Philipp Mertsch
Keyword(s):  
Cosmic Rays ◽  
Small Scale ◽  
Relative Diffusion

scholarly journals The effects of cosmic rays on the formation of Milky Way-mass galaxies in a cosmological context

2020 ◽  
Vol 497 (2) ◽  
pp. 1712-1737 ◽  
Author(s):  
Tobias Buck ◽  
Christoph Pfrommer ◽  
Rüdiger Pakmor ◽  
Robert J J Grand ◽  
Volker Springel
Keyword(s):  
Cosmic Rays ◽  
Milky Way ◽  
Gamma Ray ◽  
Transport Model ◽  
Formation Rate ◽  
Wave Model ◽  
Alfven Wave ◽  
Small Scale ◽  
Density Peaks ◽  
The Impact

ABSTRACT We investigate the impact of cosmic rays (CRs) and different modes of CR transport on the properties of Milky Way-mass galaxies in cosmological magnetohydrodynamical simulations in the context of the AURIGA project. We systematically study how advection, anisotropic diffusion, and additional Alfvén-wave cooling affect the galactic disc and the circumgalactic medium (CGM). Global properties such as stellar mass and star formation rate vary little between simulations with and without various CR transport physics, whereas structural properties such as disc sizes, CGM densities, or temperatures can be strongly affected. In our simulations, CRs affect the accretion of gas on to galaxies by modifying the CGM flow structure. This alters the angular momentum distribution that manifests itself as a difference in stellar and gaseous disc size. The strength of this effect depends on the CR transport model: CR advection results in the most compact discs while the Alfvén-wave model resembles more the AURIGA model. The advection and diffusion models exhibit large (r ∼ 50 kpc) CR pressure-dominated gas haloes causing a smoother and partly cooler CGM. The additional CR pressure smoothes small-scale density peaks and compensates for the missing thermal pressure support at lower CGM temperatures. In contrast, the Alfvén-wave model is only CR pressure dominated at the disc–halo interface and only in this model the gamma-ray emission from hadronic interactions agrees with observations. In contrast to previous findings, we conclude that details of CR transport are critical for accurately predicting the impact of CR feedback on galaxy formation.

scholarly journals Global simulations of a galactic dynamo driven by cosmic-rays and exploding magnetized stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 549-550 ◽  
Author(s):  
Michał Hanasz ◽  
Dominik Wóltański ◽  
Kacper Kowalik ◽  
Rafał Pawłaszek
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Cosmic Ray ◽  
Small Scale ◽  
Inverse Cascade ◽  
Mhd Simulations ◽  
Magnetized Stars

AbstractWe conduct global galactic–scale magnetohydrodynamical (MHD) simulations of the cosmic–ray driven dynamo. 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. Our simulations are performed with the aid of a new parallel MHD code PIERNIK. 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 by an inverse cascade promoted by resistive processes.

scholarly journals Small‐Scale Anisotropy of Cosmic Rays above 1019eV Observed with the Akeno Giant Air Shower Array

1999 ◽  
Vol 522 (1) ◽  
pp. 225-237 ◽  
Author(s):  
M. Takeda ◽  
N. Hayashida ◽  
K. Honda ◽  
N. Inoue ◽  
K. Kadota ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Small Scale ◽  
Air Shower ◽  
Shower Array ◽  
Air Shower Array

scholarly journals The power spectrum of cosmic ray arrival directions

2015 ◽  
Vol 2 ◽  
pp. 45-49 ◽  
Author(s):  
M. Ahlers
Keyword(s):  
Numerical Methods ◽  
Cosmic Rays ◽  
Power Spectrum ◽  
Large Scale ◽  
Cosmic Ray ◽  
Direct Consequence ◽  
Small Scale ◽  
Ray Diffusion ◽  
Liouville’S Theorem ◽  
Arrival Directions

Abstract. Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

scholarly journals A search for small-scale anisotropy of PeV cosmic rays

2012 ◽  
Vol 38 (11) ◽  
pp. 731-743 ◽  
Author(s):  
M. Yu. Zotov ◽  
G. V. Kulikov
Keyword(s):  
Cosmic Rays ◽  
Small Scale
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