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We investigate the diffusion of cosmic rays into molecular cloud complexes. Using the cosmic-ray diffusion formalism of Protheroe, et al. (2008), we examine how cosmic rays diffuse into clouds exhibiting different density structures,…

High Energy Astrophysical Phenomena · Physics 2015-06-22 D. I. Jones

We explore the effects of the expected higher cosmic ray (CR) ionization rates $\zeta_{\rm CR}$ on the abundances of carbon monoxide (CO), atomic carbon (C), and ionized carbon (C$^+$) in the H$_2$ clouds of star-forming galaxies. The study…

We calculate the diffusion coefficients of charged cosmic rays (CR) propagating in regular and turbulent magnetic fields. If the magnetic field is dominated by an isotropic turbulent component, we find that CRs reside too long in the…

High Energy Astrophysical Phenomena · Physics 2018-07-24 G. Giacinti , M. Kachelriess , D. V. Semikoz

Recent efforts in cosmic ray (CR) confinement and transport theory are discussed. Three problems are addressed as being crucial for understanding the present day observations and their possible telltale signs of the CR origin. The first…

High Energy Astrophysical Phenomena · Physics 2016-10-11 M. A. Malkov

The acceleration of cosmic ray particles and their propagation in the Milky Way and the heliosphere tangle with each other, leading to complexity and degeneracy of the modeling of Galactic cosmic rays (GCRs). The recent measurements of the…

High Energy Astrophysical Phenomena · Physics 2018-08-22 Cheng-Rui Zhu , Qiang Yuan , Da-Ming Wei

Observations of molecular clouds in the gamma ray domain provide us with a tool to study the distribution of cosmic rays in the Galaxy. This is because cosmic rays can penetrate molecular clouds, undergo hadronic interactions in the dense…

High Energy Astrophysical Phenomena · Physics 2017-08-23 Stefano Gabici

We have obtained estimates for the cosmic-ray ionization rate (CRIR) in the Galactic disk, using a detailed model for the physics and chemistry of diffuse interstellar gas clouds to interpret previously-published measurements of the…

Astrophysics of Galaxies · Physics 2017-08-30 David A. Neufeld , Mark G. Wolfire

We investigate how cosmic rays (CRs) affect thermal and hydrostatic stability of circumgalactic (CGM) gas, in simulations with both CR streaming and diffusion. Local thermal instability can be suppressed by CR-driven entropy mode…

Astrophysics of Galaxies · Physics 2023-05-25 Tsun Hin Navin Tsung , S. Peng Oh , Chad Bustard

Numerical simulations shed light onto earlier not trackable problem of magnetohydrodynamic (MHD) turbulence. They allowed to test the predictions of different models and choose the correct ones. Inevitably, this progress calls for revisions…

Astrophysics · Physics 2007-12-27 Huirong Yan , A. Lazarian

The most recent observational evidence seems to indicate that giant molecular clouds are predominantly gravitationally unbound objects. In this paper we show that this is a natural consequence of a scenario in which cloud-cloud collisions…

Astrophysics of Galaxies · Physics 2015-05-27 C. L. Dobbs , A. Burkert , J. E. Pringle

Merging galaxy clusters exhibit strong observational evidence for efficient particle acceleration in the intracluster medium (ICM), particularly in the form of synchrotron-emitting radio relics and halos. Cosmic ray (CR) electrons are…

High Energy Astrophysical Phenomena · Physics 2025-10-29 Rebecca Diesing , Ludwig Böss , Damiano Caprioli

Cosmic rays (CRs) play a major role in the dynamics of the interstellar medium (ISM). Their interactions and transport ionize, heat, and push the ISM thereby coupling different regions of it. The spatial distribution of CRs depends on the…

We propose and experimentally validate the use of rotational echo responses for obtaining the degree of molecular alignment induced in a gas. The method is independent of various parameters that are hardly accessible in most experimental…

Chemical Physics · Physics 2020-07-01 Dina Rosenberg , Sharly Fleischer

Cosmic rays are the only agent able to penetrate into the interior of dense molecular clouds. Depositing (part of) their energy through ionisation, cosmic rays play an essential role in determining the physical and chemical evolution of…

High Energy Astrophysical Phenomena · Physics 2023-06-21 Vo Hong Minh Phan , Sarah Recchia , Philipp Mertsch , Stefano Gabici

Understanding cosmic ray (CR) diffusion in a partially ionized medium is both crucial and challenging. In this study, we investigate CR perpendicular superdiffusion and parallel transport in turbulent, partially ionized media using…

Astrophysics of Galaxies · Physics 2025-10-09 Yue Hu , Siyao Xu , Alex Lazarian , James M. Stone , Philip F. Hopkins

We investigate the diffusion of cosmic rays (CR) close to their sources. Propagating individual CRs in purely isotropic turbulent magnetic fields with maximal scale of spatial variations Lmax, we find that CRs diffuse anisotropically at…

High Energy Astrophysical Phenomena · Physics 2012-06-29 G. Giacinti , M. Kachelriess , D. V. Semikoz

The growth of magneto-hydrodynamic fluctuations relevant to cosmic ray confinement in and near their sources, and the effects of local plasma conditions is revisited. We consider cases where cosmic rays penetrate a medium which may contain…

High Energy Astrophysical Phenomena · Physics 2021-02-10 B. Reville , G. Giacinti , R. Scott

Cosmic-ray (CR) sources temporarily enhance the relativistic particle density in their vicinity over the background distribution accumulated from the Galaxy-wide past injection activity and propagation. If individual sources are close…

High Energy Astrophysical Phenomena · Physics 2021-08-18 Guðlaugur Jóhannesson , Troy A. Porter

Recent studies have suggested that low-energy cosmic rays (CRs) may be accelerated inside molecular clouds by the shocks associated with star formation. We use a Monte Carlo transport code to model the propagation of CRs accelerated by…

Recent advances on gamma-ray observations from SuperNova Remnants and Molecular Clouds offer the possibility to study in detail the properties of the propagation of escaping Cosmic Rays (CR). However, a complete theory for CR transport…

High Energy Astrophysical Phenomena · Physics 2015-09-09 Lara Nava , Stefano Gabici , Alexandre Marcowith , Giovanni Morlino , Vladimir Ptuskin