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Under nonuniform convection, the distribution of diffusive particles can exhibit dipole and quadrupole anisotropy induced by the fluid inertial and shear force, respectively. These convection-related anisotropies, unlike the Compton-Getting…

High Energy Astrophysical Phenomena · Physics 2022-10-26 Yiran Zhang , Siming Liu , Dejin Wu

Determining the spatial distribution of Galactic cosmic rays (CRs) is fundamental to understand how these particles propagate in interstellar space and to infer their source spectra. The most sensitive method of studying this problem is…

High Energy Astrophysical Phenomena · Physics 2025-09-26 Paolo Lipari , Silvia Vernetto

The standard approach to cosmic-ray (CR) propagation in the Galaxy is based on the assumption that local transport properties can be extrapolated to the whole CR confining volume. Such models tend to underestimate the gamma-ray flux above…

High Energy Astrophysical Phenomena · Physics 2015-05-06 Daniele Gaggero , Alfredo Urbano , Mauro Valli , Piero Ullio

Galactic cosmic rays (CRs) play a crucial role in galaxy formation and evolution by altering gas dynamics and chemistry across multiple scales. Typical numerical simulations of CR transport assume a constant diffusion coefficient for the…

Astrophysics of Galaxies · Physics 2025-10-16 Sarah Thiele , Romain Teyssier

Understanding the transport of energetic cosmic rays belongs to the most challenging topics in astrophysics. Diffusion due to scattering by electromagnetic fluctuations is a key process in cosmic-ray transport. The transition from a…

High Energy Astrophysical Phenomena · Physics 2020-09-02 P. Reichherzer , J. Becker Tjus , E. G. Zweibel , L. Merten , M. J. Pueschel

Dynamically, cosmic rays with energies above about one GeV/nucleon may be important agents of galaxy evolution. Their pressures compare with the thermal and magnetic ones impacting galactic gas accretion, fountains and galactic outflows,…

High Energy Astrophysical Phenomena · Physics 2022-05-18 A. Nuñez-Castiñeyra , I. A. Grenier , F. Bournaud , Y. Dubois , F. R. Kamal Youssef , P. Hennebelle

A flux of cosmic rays (CRs) propagating through a diffuse ionized gas can excite MHD waves, thus generating magnetic disturbances. We propose a generic model of CR penetration into molecular clouds through their diffuse envelopes, and…

High Energy Astrophysical Phenomena · Physics 2018-03-14 A. V. Ivlev , V. A. Dogiel , D. O. Chernyshov , P. Caselli , C. -M. Ko , K. S. Cheng

Cosmic-ray transport in astrophysical environments is often dominated by the diffusion of particles in a magnetic field composed of both a turbulent and a mean component. This process, which is two-fold turbulent mixing in that the particle…

High Energy Astrophysical Phenomena · Physics 2021-12-14 P. Reichherzer , L. Merten , J. Dörner , J. Becker Tjus , M. J. Pueschel , E. G. Zweibel

We introduce a novel diffusion model for the propagation of cosmic rays (CRs) that incorporates an anisotropic diffusion tensor of a general form within a realistically modeled large-scale Galactic magnetic field. The parameters of the…

High Energy Astrophysical Phenomena · Physics 2025-07-22 V. D. Borisov , V. O. Yurovsky , I. A. Kudryashov

A rapidly growing amount of evidences, mostly coming from the recent gamma-ray observations of Galactic supernova remnants (SNRs), is seriously challenging our understanding of how particles are accelerated at fast shocks. The cosmic-ray…

High Energy Astrophysical Phenomena · Physics 2015-06-05 Damiano Caprioli

We show that the large-scale cosmic ray anisotropy at ~10 TeV can be explained by a modified Compton-Getting effect in the magnetized flow field of old supernova remnants. This approach suggests an optimum energy scale for detecting the…

High Energy Astrophysical Phenomena · Physics 2015-06-05 P. L. Biermann , J. K. Becker , E. -S. Seo , M. Mandelartz

It has been alleged in several papers that the so called delayed continuous-time random walks (DCTRWs) provide a model for the one-dimensional telegraph equation at microscopic level. This conclusion, being widespread now, is strange, since…

Statistical Mechanics · Physics 2012-03-01 Sergey A. Rukolaine , Alexander M. Samsonov

More and more observations have indicated the existence of slow diffusion phenomena in astrophysical environments, such as around the supernova remnants and pulsar $\gamma$-ray halos, where the diffusion coefficient of cosmic rays (CRs)…

High Energy Astrophysical Phenomena · Physics 2025-06-24 Yawen Xiao , Jianfu Zhang , Siyao Xu

We review numerical methods for simulations of cosmic ray (CR) propagation on galactic and larger scales. We present the development of algorithms designed for phenomenological and self-consistent models of CR propagation in kinetic…

High Energy Astrophysical Phenomena · Physics 2021-06-17 M. Hanasz , A. Strong , P. Girichidis

We analyse the transport of cosmic rays (CR) in magnetic fields that are structured on scales greater than the CR Larmor radius. We solve the Vlasov-Fokker-Planck (VFP) equation for various mixes of mirroring and small-angle scattering and…

High Energy Astrophysical Phenomena · Physics 2025-04-09 A. R. Bell , J. H. Matthews , A. M. Taylor , G. Giacinti

Cosmic ray (CR) propagation is controlled by scattering in turbulent magnetic fields in space. In general, diffusive propagation is governed by pitch-angle diffusion in phase space. In this study, pitch-angle diffusion in the local…

High Energy Astrophysical Phenomena · Physics 2026-05-26 Huirong Yan , Siqi Zhao , Ming Zhang

A crucial process in Galactic cosmic-ray (CR) transport is the spatial diffusion due to the interaction with the interstellar turbulent magnetic field. Usually, CR diffusion is assumed to be uniform and isotropic all across the Galaxy.…

High Energy Astrophysical Phenomena · Physics 2017-10-25 Silvio Sergio Cerri , Daniele Gaggero , Andrea Vittino , Carmelo Evoli , Dario Grasso

In the standard picture of cosmic ray transport the propagation of charged cosmic rays through turbulent magnetic fields is described as a random walk with cosmic rays scattering on magnetic field turbulence. This is in good agreement with…

High Energy Astrophysical Phenomena · Physics 2021-07-08 Marco Kuhlen , Philipp Mertsch , Vo Hong Minh Phan

One of the unsolved problems in cosmic ray (CR) physics is the small radial gradient of the gamma-ray intensity compared to the inferred CR source distribution in the Galactic disk. In diffusive CR propagation models the most natural…

Astrophysics · Physics 2007-05-23 D. Breitschwerdt , V. Dogiel , H. J. V"olk

While it is well-known that cosmic rays (CRs) can gain energy from turbulence via second order Fermi acceleration, how this energy transfer affects the turbulent cascade remains largely unexplored. Here, we show that damping and steepening…

High Energy Astrophysical Phenomena · Physics 2023-08-15 Chad Bustard , S. Peng Oh