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Journal articles on the topic 'Cosmic-ray transport'

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Published: 14 March 2023

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1

Schlickeiser, Reinhard. "Cosmic-ray transport and acceleration." Astrophysical Journal Supplement Series 90 (February 1994): 929. http://dx.doi.org/10.1086/191927.

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2

Biermann, Peter L., Julia Becker Tjus, Eun-Suk Seo, and Matthias Mandelartz. "COSMIC-RAY TRANSPORT AND ANISOTROPIES." Astrophysical Journal 768, no. 2 (April 22, 2013): 124. http://dx.doi.org/10.1088/0004-637x/768/2/124.

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3

Duffy, Peter, and Katherine M. Blundell. "Cosmic ray transport and acceleration." Plasma Physics and Controlled Fusion 47, no. 12B (November 11, 2005): B667—B678. http://dx.doi.org/10.1088/0741-3335/47/12b/s49.

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4

Schlickeiser, Reinhard. "Cosmic-Ray Transport and Acceleration." International Astronomical Union Colloquium 142 (1994): 926–36. http://dx.doi.org/10.1017/s0252921100078337.

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AbstractWe review the transport and acceleration of cosmic rays concentrating on the origin of galactic cosmic rays. Quasi-linear theory for the acceleration rates and propagation parameters of charged test particles combined with the plasma wave viewpoint of modeling weak cosmic electromagnetic turbulence provides a qualitatively and quantitatively correct description of key observations. Incorporating finite frequency effects, dispersion, and damping of the plasma waves are essential in overcoming classical discrepancies with observations as the Kfit - Kql discrepancy of solar particle events. We show that the diffusion-convection transport equation in its general form contains spatial convection and diffusion terms as well as momentum convection and diffusion terms. In particular, the latter momentum diffusion term plays a decisive role in the acceleration of cosmic rays at super-Alfvénic supernova shock fronts, and in the acceleration of ultra-high-energy cosmic rays by distributed acceleration in our own galaxy.Subject headings: acceleration of particles — convection — cosmic rays — diffusion — shock waves
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5

Maiti, Snehanshu, Kirit Makwana, Heshou Zhang, and Huirong Yan. "Cosmic-ray Transport in Magnetohydrodynamic Turbulence." Astrophysical Journal 926, no. 1 (February 1, 2022): 94. http://dx.doi.org/10.3847/1538-4357/ac46c8.

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Abstract This paper studies cosmic-ray (CR) transport in magnetohydrodynamic (MHD) turbulence. CR transport is strongly dependent on the properties of the magnetic turbulence. We perform test particle simulations to study the interactions of CR with both total MHD turbulence and decomposed MHD modes. The spatial diffusion coefficients and the pitch angle scattering diffusion coefficients are calculated from the test particle trajectories in turbulence. Our results confirm that the fast modes dominate the CR propagation, whereas Alfvén and slow modes are much less efficient and have shown similar pitch-angle scattering rates. We investigate the cross field transport on large and small scales. On large/global scales, normal diffusion is observed and the diffusion coefficient is suppressed by M A ζ compared to the parallel diffusion coefficients, with ζ closer to 4 in Alfvén modes than that in total turbulence, as theoretically expected. For the CR transport on scales smaller than the turbulence injection scale, both the local and global magnetic reference frames are adopted. Superdiffusion is observed on such small scales in all the cases. Particularly, CR transport in Alfvén modes show clear Richardson diffusion in the local reference frame. The diffusion transitions smoothly from the Richardson’s one with index 1.5 to normal diffusion as the particle mean free path decreases from λ ∥ ≫ L to λ ∥ ≪ L, where L is the injection/coherence length of turbulence. Our results have broad applications to CRs in various astrophysical environments.
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6

Strauss, R. D., J. P. van den Berg, and J. S. Rankin. "Cosmic-Ray Transport near the Sun." Astrophysical Journal 928, no. 1 (March 1, 2022): 22. http://dx.doi.org/10.3847/1538-4357/ac582a.

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Abstract The strongly diverging magnetic field lines in the very inner heliosphere, through the associated magnetic focusing/mirroring forces, can, potentially, lead to highly anisotropic galactic cosmic-ray distributions close to the Sun. Using a simplified analytical approach, validated by numerical simulations, we study the behavior of the galactic cosmic-ray distribution in this newly explored region of the heliosphere and find that significant anisotropies can be expected inside 0.2 au.
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7

Strauss, R. D., H. Fichtner, M. S. Potgieter, J. A. le Roux, and X. Luo. "Cosmic ray transport near the heliopause." Journal of Physics: Conference Series 642 (September 2015): 012026. http://dx.doi.org/10.1088/1742-6596/642/1/012026.

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8

Krumholz, Mark R., Roland M. Crocker, Siyao Xu, A. Lazarian, M. T. Rosevear, and Jasper Bedwell-Wilson. "Cosmic ray transport in starburst galaxies." Monthly Notices of the Royal Astronomical Society 493, no. 2 (February 18, 2020): 2817–33. http://dx.doi.org/10.1093/mnras/staa493.

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ABSTRACT Starburst galaxies are efficient γ-ray producers, because their high supernova rates generate copious cosmic ray (CR) protons, and their high gas densities act as thick targets off which these protons can produce neutral pions and thence γ-rays. In this paper, we present a first-principles calculation of the mechanisms by which CRs propagate through such environments, combining astrochemical models with analysis of turbulence in weakly ionized plasma. We show that CRs cannot scatter off the strong large-scale turbulence found in starbursts, because efficient ion-neutral damping prevents such turbulence from cascading down to the scales of CR gyroradii. Instead, CRs stream along field lines at a rate determined by the competition between streaming instability and ion-neutral damping, leading to transport via a process of field line random walk. This results in an effective diffusion coefficient that is nearly energy independent up to CR energies of ∼1 TeV. We apply our computed diffusion coefficient to a simple model of CR escape and loss, and show that the resulting γ-ray spectra are in good agreement with the observed spectra of the starbursts NGC 253, M82, and Arp 220. In particular, our model reproduces these galaxies’ relatively hard GeV γ-ray spectra and softer TeV spectra without the need for any fine-tuning of advective escape times or the shape of the CR injection spectrum.
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9

Ptuskin, Vladimir. "Cosmic ray transport in the Galaxy." Journal of Physics: Conference Series 47 (October 1, 2006): 113–19. http://dx.doi.org/10.1088/1742-6596/47/1/014.

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10

Schlickeiser, R. "Cosmic ray transport in astrophysical plasmas." Physics of Plasmas 22, no. 9 (September 2015): 091502. http://dx.doi.org/10.1063/1.4928940.

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11

Kirk, John G., Peter Schneider, and Reinhard Schlickeiser. "Cosmic-ray transport in accelerating flows." Astrophysical Journal 328 (May 1988): 269. http://dx.doi.org/10.1086/166290.

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12

Tautz, R. C. "Ergodicity of perpendicular cosmic ray transport." Astronomy & Astrophysics 591 (June 24, 2016): A125. http://dx.doi.org/10.1051/0004-6361/201628391.

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13

Shalchi, A. "Cosmic ray transport in strong turbulence." Monthly Notices of the Royal Astronomical Society 363, no. 1 (October 11, 2005): 107–11. http://dx.doi.org/10.1111/j.1365-2966.2005.09424.x.

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14

Thomas, T., and C. Pfrommer. "Cosmic-ray hydrodynamics: Alfvén-wave regulated transport of cosmic rays." Monthly Notices of the Royal Astronomical Society 485, no. 3 (January 25, 2019): 2977–3008. http://dx.doi.org/10.1093/mnras/stz263.

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15

Armillotta, Lucia, Eve C. Ostriker, and Yan-Fei Jiang. "Cosmic-Ray Transport in Simulations of Star-forming Galactic Disks." Astrophysical Journal 922, no. 1 (November 1, 2021): 11. http://dx.doi.org/10.3847/1538-4357/ac1db2.

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Abstract Cosmic-ray transport on galactic scales depends on the detailed properties of the magnetized, multiphase interstellar medium (ISM). In this work, we postprocess a high-resolution TIGRESS magnetohydrodynamic simulation modeling a local galactic disk patch with a two-moment fluid algorithm for cosmic-ray transport. We consider a variety of prescriptions for the cosmic rays, from a simple, purely diffusive formalism with constant scattering coefficient, to a physically motivated model in which the scattering coefficient is set by the critical balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We separately focus on cosmic rays with kinetic energies of ∼1 GeV (high-energy) and ∼30 MeV (low energy), respectively important for ISM dynamics and chemistry. We find that simultaneously accounting for advection, streaming, and diffusion of cosmic rays is crucial for properly modeling their transport. Advection dominates in the high-velocity, low-density hot phase, while diffusion and streaming are more important in higher-density, cooler phases. Our physically motivated model shows that there is no single diffusivity for cosmic-ray transport: the scattering coefficient varies by four or more orders of magnitude, maximal at density n H ∼ 0.01 cm−3. The ion-neutral damping of Alfvén waves results in strong diffusion and nearly uniform cosmic-ray pressure within most of the mass of the ISM. However, cosmic rays are trapped near the disk midplane by the higher scattering rate in the surrounding lower-density, higher-ionization gas. The transport of high-energy cosmic rays differs from that of low-energy cosmic rays, with less effective diffusion and greater energy losses for the latter.
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16

Ferreira, Stefan E. S. "Theory of cosmic ray modulation." Proceedings of the International Astronomical Union 4, S257 (September 2008): 429–38. http://dx.doi.org/10.1017/s1743921309029664.

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AbstractThis work aims to give a brief overview on the topic of cosmic ray modulation in the heliosphere. The heliosphere, heliospheric magnetic field, transport parameters and the transport equation together with modulation models, which solve this equation in various degree of complexity, are briefly discussed. Results from these models are then presented where first it is shown how cosmic rays are globally distributed in an asymmetrical heliosphere which results from the relative motion between the local interstellar medium and the Sun. Next the focus shifts to low-energy Jovian electrons. The intensities of these electrons, which originate from a point source in the inner heliosphere, exhibit a unique three-dimensional spiral structure where most of the particles are transported along the magnetic field lines. Time-dependent modulation is also discussed where it is shown how drift effects together with propagating diffusion barriers are responsible for modulation over a solar cycle.
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17

Armillotta, Lucia, Eve C. Ostriker, and Yan-Fei Jiang. "Cosmic-Ray Transport in Varying Galactic Environments." Astrophysical Journal 929, no. 2 (April 1, 2022): 170. http://dx.doi.org/10.3847/1538-4357/ac5fa9.

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Abstract We study the propagation of mildly relativistic cosmic rays (CRs) in multiphase interstellar medium environments with conditions typical of nearby disk galaxies. We employ the techniques developed in Armillotta et al. to postprocess three high-resolution TIGRESS magnetohydrodynamic simulations modeling local patches of star-forming galactic disks. Together, the three simulations cover a wide range of gas surface density, gravitational potential, and star formation rate (SFR). Our prescription for CR propagation includes the effects of advection by the background gas, streaming along the magnetic field at the local ion Alfvén speed, and diffusion relative to the Alfvén waves, with the diffusion coefficient set by the balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We find that the combined transport processes are more effective in environments with higher SFR. These environments are characterized by higher-velocity hot outflows (created by clustered supernovae) that rapidly advect CRs away from the galactic plane. As a consequence, the ratio of midplane CR pressure to midplane gas pressures decreases with increasing SFR. We also use the postprocessed simulations to make predictions regarding the potential dynamical impacts of CRs. The relatively flat CR pressure profiles near the midplane argue that they would not provide significant support against gravity for most of the ISM mass. However, the CR pressure gradients are larger than the other pressure gradients in the extraplanar region (∣z∣ > 0.5 kpc), suggesting that CRs may affect the dynamics of galactic fountains and/or winds. The degree of this impact is expected to increase in environments with lower SFR.
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18

Armillotta, Lucia, Eve C. Ostriker, and Yan-Fei Jiang. "Cosmic-Ray Transport in Varying Galactic Environments." Astrophysical Journal 929, no. 2 (April 1, 2022): 170. http://dx.doi.org/10.3847/1538-4357/ac5fa9.

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Abstract We study the propagation of mildly relativistic cosmic rays (CRs) in multiphase interstellar medium environments with conditions typical of nearby disk galaxies. We employ the techniques developed in Armillotta et al. to postprocess three high-resolution TIGRESS magnetohydrodynamic simulations modeling local patches of star-forming galactic disks. Together, the three simulations cover a wide range of gas surface density, gravitational potential, and star formation rate (SFR). Our prescription for CR propagation includes the effects of advection by the background gas, streaming along the magnetic field at the local ion Alfvén speed, and diffusion relative to the Alfvén waves, with the diffusion coefficient set by the balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We find that the combined transport processes are more effective in environments with higher SFR. These environments are characterized by higher-velocity hot outflows (created by clustered supernovae) that rapidly advect CRs away from the galactic plane. As a consequence, the ratio of midplane CR pressure to midplane gas pressures decreases with increasing SFR. We also use the postprocessed simulations to make predictions regarding the potential dynamical impacts of CRs. The relatively flat CR pressure profiles near the midplane argue that they would not provide significant support against gravity for most of the ISM mass. However, the CR pressure gradients are larger than the other pressure gradients in the extraplanar region (∣z∣ > 0.5 kpc), suggesting that CRs may affect the dynamics of galactic fountains and/or winds. The degree of this impact is expected to increase in environments with lower SFR.
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19

Shalchi, A., and R. Schlickeiser. "Cosmic ray transport in anisotropic magnetohydrodynamic turbulence." Astronomy & Astrophysics 420, no. 3 (June 2004): 799–808. http://dx.doi.org/10.1051/0004-6361:20034304.

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20

Norbury, John W., Lawrence W. Townsend, and Ryan B. Norman. "Threshold meson production and cosmic ray transport." Journal of Physics G: Nuclear and Particle Physics 34, no. 1 (November 8, 2006): 115–21. http://dx.doi.org/10.1088/0954-3899/34/1/007.

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21

Tautz, R. C., and A. Shalchi. "On the diffusivity of cosmic ray transport." Journal of Geophysical Research: Space Physics 115, A3 (March 2010): n/a. http://dx.doi.org/10.1029/2009ja014944.

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22

Shalchi, A., and R. Schlickeiser. "Cosmic ray transport in anisotropic magnetohydrodynamic turbulence." Astronomy & Astrophysics 454, no. 1 (July 2006): 1–9. http://dx.doi.org/10.1051/0004-6361:20054572.

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23

Tautz, R. C., A. Dosch, and I. Lerche. "Simulating cosmic-ray transport with adiabatic focusing." Astronomy & Astrophysics 545 (September 2012): A149. http://dx.doi.org/10.1051/0004-6361/201219636.

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24

Lerche, I., and R. Schlickeiser. "Cosmic ray transport in anisotropic magnetohydrodynamic turbulence." Astronomy & Astrophysics 378, no. 1 (October 2001): 279–94. http://dx.doi.org/10.1051/0004-6361:20011080.

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25

Giacalone, Joe. "Cosmic-Ray Transport and Interaction with Shocks." Space Science Reviews 176, no. 1-4 (March 18, 2011): 73–88. http://dx.doi.org/10.1007/s11214-011-9763-2.

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26

Teufel, A., I. Lerche, and R. Schlickeiser. "Cosmic ray transport in anisotropic magnetohydrodynamic turbulence." Astronomy & Astrophysics 397, no. 3 (January 2003): 777–88. http://dx.doi.org/10.1051/0004-6361:20021548.

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27

Buchvarova, M., and D. Draganov. "Model of galactic cosmic ray spectrum above the Earth’s atmosphere." Journal of Physics: Conference Series 2255, no. 1 (April 1, 2022): 012004. http://dx.doi.org/10.1088/1742-6596/2255/1/012004.

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Abstract Galactic cosmic ray transport in the heliosphere is described by the well-known Parker transport equation. In 1969, Fisk and Axford [1] presented approximate analytical solutions to the cosmic ray transport equation. One of their solutions was later used to construct useful semi-empirical models describing the energy spectra of charged particles during the solar cycle. In this paper, a simplified model of the galactic cosmic ray spectrum is presented. The model can be used to describe the galactic spectra of protons and helium nuclei during the 11-year solar cycle in interplanetary space at about 1 AU.
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28

Fitz Axen, Margot, Julia Speicher, Aimee Hungerford, and Chris L. Fryer. "Cosmic ray transport in mixed magnetic fields and their role on the observed anisotropies." Monthly Notices of the Royal Astronomical Society 500, no. 3 (November 13, 2020): 3497–510. http://dx.doi.org/10.1093/mnras/staa3500.

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ABSTRACT There is a growing set of observational data demonstrating that cosmic rays exhibit small-scale anisotropies (5°–30°) with amplitude deviations lying between 0.01–0.1 per cent that of the average cosmic ray flux. A broad range of models have been proposed to explain these anisotropies ranging from finite-scale magnetic field structures to dark matter annihilation. The standard diffusion transport methods used in cosmic ray propagation do not capture the transport physics in a medium with finite-scale or coherent magnetic field structures. Here, we present a Monte Carlo transport method, applying it to a series of finite-scale magnetic field structures to determine the requirements of such fields in explaining the observed cosmic ray, small-scale anisotropies.
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29

Harding, A. K., A. Mastichiadis, R. J. Protheroe, and A. P. Szabo. "Cosmic-ray transport and gamma-ray emission in supernova shells." Astrophysical Journal 378 (September 1991): 163. http://dx.doi.org/10.1086/170416.

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30

Biermann, P. L., L. I. Caramete, A. Meli, B. N. Nath, E. S. Seo, V. de Souza, and J. Becker Tjus. "Cosmic ray transport and anisotropies to high energies." ASTRA Proceedings 2 (October 2, 2015): 39–44. http://dx.doi.org/10.5194/ap-2-39-2015.

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Abstract. A model is introduced, in which the irregularity spectrum of the Galactic magnetic field beyond the dissipation length scale is first a Kolmogorov spectrum k-5/3 at small scales λ = 2 π/k with k the wave-number, then a saturation spectrum k-1, and finally a shock-dominated spectrum k-2 mostly in the halo/wind outside the Cosmic Ray disk. In an isotropic approximation such a model is consistent with the Interstellar Medium (ISM) data. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.
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31

ZuHone, John, Kristian Ehlert, Rainer Weinberger, and Christoph Pfrommer. "Turning AGN Bubbles into Radio Relics with Sloshing: Modeling CR Transport with Realistic Physics." Galaxies 9, no. 4 (November 3, 2021): 91. http://dx.doi.org/10.3390/galaxies9040091.

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Radio relics are arc-like synchrotron sources at the periphery of galaxy clusters, produced by cosmic-ray electrons in a μG magnetic field, which are believed to have been (re-)accelerated by merger shock fronts. However, not all relics appear at the same location as shocks as seen in the X-ray. In a previous work, we suggested that the shape of some relics may result from the pre-existing spatial distribution of cosmic-ray electrons, and tested this hypothesis using simulations by launching AGN jets into a cluster atmosphere with sloshing gas motions generated by a previous merger event. We showed that these motions could transport the cosmic ray-enriched material of the AGN bubbles to large radii and stretch it in a tangential direction, producing a filamentary shape resembling a radio relic. In this work, we improve our physical description for the cosmic rays by modeling them as a separate fluid which undergoes diffusion and Alfvén losses. We find that, including this additional cosmic ray physics significantly diminishes the appearance of these filamentary features, showing that our original hypothesis is sensitive to the modeling of cosmic ray physics in the intracluster medium.
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32

Sigalo, F. B., and F. E. Opara. "Model of Radiation Transport at Cosmic Ray Shocks." Research Journal of Applied Sciences 7, no. 8 (August 1, 2012): 391–96. http://dx.doi.org/10.3923/rjasci.2012.391.396.

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33

Ivascenko, A., and F. Spanier. "Semi-analytical model of cosmic ray electron transport." Astrophysics and Space Sciences Transactions 7, no. 3 (July 5, 2011): 265–69. http://dx.doi.org/10.5194/astra-7-265-2011.

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34

Jiang, Yan-Fei, and S. Peng Oh. "A New Numerical Scheme for Cosmic-Ray Transport." Astrophysical Journal 854, no. 1 (February 22, 2018): 5. http://dx.doi.org/10.3847/1538-4357/aaa6ce.

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35

Farber, R., M. Ruszkowski, H. Y. K. Yang, and E. G. Zweibel. "Impact of Cosmic-Ray Transport on Galactic Winds." Astrophysical Journal 856, no. 2 (March 29, 2018): 112. http://dx.doi.org/10.3847/1538-4357/aab26d.

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36

Maurin, D., A. Putze, and L. Derome. "Systematic uncertainties on the cosmic-ray transport parameters." Astronomy and Astrophysics 516 (June 2010): A67. http://dx.doi.org/10.1051/0004-6361/201014011.

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37

Lagutin, A. A., and V. V. Uchaikin. "Anomalous diffusion equation: Application to cosmic ray transport." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 201, no. 1 (January 2003): 212–16. http://dx.doi.org/10.1016/s0168-583x(02)01362-9.

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38

Wilson, John W., and Lawrence W. Townsend. "A Benchmark for Galactic Cosmic-Ray Transport Codes." Radiation Research 114, no. 2 (May 1988): 201. http://dx.doi.org/10.2307/3577217.

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39

Shalchi, A. "Second-order quasilinear theory of cosmic ray transport." Physics of Plasmas 12, no. 5 (May 2005): 052905. http://dx.doi.org/10.1063/1.1895805.

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40

Amato, Elena, and Pasquale Blasi. "Cosmic ray transport in the Galaxy: A review." Advances in Space Research 62, no. 10 (November 2018): 2731–49. http://dx.doi.org/10.1016/j.asr.2017.04.019.

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41

EVENSON, PAUL, and EVELYN B. TUSKA. "Cosmic Ray Transport — Modulation and the Anomalous Component." Reviews of Geophysics 29, S2 (January 1991): 944–54. http://dx.doi.org/10.1002/rog.1991.29.s2.944.

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42

Recchia, Sarah. "Cosmic ray driven galactic winds." International Journal of Modern Physics D 29, no. 07 (May 2020): 2030006. http://dx.doi.org/10.1142/s0218271820300062.

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Galactic winds constitute a primary feedback process in the ecology and evolution of galaxies. They are ubiquitously observed and exhibit a rich phenomenology, whose origin is actively investigated both theoretically and observationally. Cosmic rays have been widely recognized as a possible driving agent of galactic winds, especially in Milky–Way like galaxies. The formation of cosmic ray-driven winds is intimately connected with the microphysics of the cosmic ray transport in galaxies, making it an intrinsically non-linear and multiscale phenomenon. In this complex interplay, the cosmic ray distribution affects the wind launching and, in turns, is shaped by the presence of winds. In this review, we summarize the present knowledge of the physics of cosmic rays involved in the wind formation and of the wind hydrodynamics. We also discuss the theoretical difficulties connected with the study of cosmic ray-driven winds and possible future improvements and directions.
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43

Wiener, Joshua, and Ellen G. Zweibel. "Constraints on cosmic-ray transport in galaxy clusters from radio and γ-ray observations." Monthly Notices of the Royal Astronomical Society 488, no. 1 (June 20, 2019): 280–94. http://dx.doi.org/10.1093/mnras/stz1705.

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ABSTRACT The nature of cosmic rays (CRs) and their transport in galaxy clusters is probed by several observations. Radio observations reveal synchrotron radiation of cosmic-ray electrons (CRe) spiralling around cluster magnetic fields. γ-ray observations reveal hadronic reactions of cosmic-ray protons (CRp) with gas nuclei that produce pions. No such cluster-wide γ-ray signal has been measured, putting an upper limit on the density of CRp in clusters. But the presence of CRe implies some source of CRp, and consequently there must be some CRp-loss mechanism. We quantify the observational constraints on this mechanism assuming that losses are dominated by CR transport, ultimately deriving lower limits on this transport. Using the Coma cluster as an example, we find that bulk outward speeds of 10–100 km s−1 are sufficient to reduce γ-radiation below current upper limits. These speeds are sub-Alfvénic and are consistent with a self-confinement model for CR transport if the magnetic field is coherent on large scales. If the transport is diffusive, we require minimum diffusion coefficients of 1031–1032 cm2 s−1. This is consistent with CRs free streaming at the speed of light along a field tangled on length-scales of a few kpc. We find that a model of the Coma cluster with a tangled field and the self-confinement picture together can be consistent with observations if the relative acceleration efficiency of CR protons is less than 15 times more than that of electrons of the same energy. This value is 3–6 times lower than the same quantity for Galactic cosmic rays.
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44

Tjus, Julia Becker. "Plasmas, particles and photons—spotlights on multimessenger astronomy." Plasma Physics and Controlled Fusion 64, no. 4 (March 14, 2022): 044013. http://dx.doi.org/10.1088/1361-6587/ac57ce.

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Abstract During the past decennia, progress in the area of high-energy astroparticle physics was exceptional, mainly due to the great success of the bridging of particle- and astrophysics both in theory and in the instrumentation of astroparticle physics observatories. Multimessenger data coming from charged cosmic-ray-, gamma-ray- and neutrino-observatories start to shed more and more light on the nature and origin of cosmic rays. At the same time, the development of methods for the investigation of cosmic-ray transport, acceleration and interaction has advanced to the true potential of tying these different pieces of multimessenger data together, this way closing in on the origin of cosmic rays. In recent years, this rapid interplay between modeling and observations has made it clear that it is essential to add the ingredient of plasma physics to the problem. It has been shown that even the interpretation of data of highly relativistic cosmic rays at TeV energies and above is in need of a proper modeling of the plasma physics involved. One of the most important examples is the understanding of wave-particle interactions. In simulations of cosmic-ray transport in the Galaxy, the cosmic-ray diffusion coefficient is typically approximated with a Kolmogorov-type cascade model, resulting in an energy-dependent parallel diffusion coefficient κ ∥ ∝ E γ with γ = 1 / 3 . Here, we show how the energy dependence of the diffusion coefficient can be investigated systematically as a function of δ B / B . The complex energy behavior that goes well beyond a simple powerlaw interpretation will be presented together with a formal definition of an energy range that indeed can be approximated as a powerlaw. These results are applied to cosmic-ray transport in the Milky Way. Finally, the transition between the ballistic and diffusive regime will be investigated for astrophysical sources with special focus on relativistic plasmoids of active galaxies.
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45

Jones, T. W. "Time-Dependent Simulation of Cosmic-Ray Shocks, Including Alfvén Transport." International Astronomical Union Colloquium 142 (1994): 969–73. http://dx.doi.org/10.1017/s0252921100078404.

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AbstractTime evolution of plane, cosmic-ray modified shocks has been simulated numerically for the case with parallel magnetic fields. Computations were done in a “three-fluid” dynamical model incorporating cosmic-ray and Alfvén-wave energy transport equations. Nonlinear feedback from the cosmic rays and Alfvén waves is included in the equation of motion for the underlying plasma, as is the finite propagation speed and energy dissipation of the Alfvén waves. Exploratory results confirm earlier, steady state analyses that found these Alfvén transport effects to be potentially important when the upstream Alfvén speed and gas sound speeds are comparable. As noted earlier, Alfvén transport effects tend to reduce the transfer of energy through a shock from gas to energetic particles. These studies show as well that the timescale for modification of the shock is altered in nonlinear ways. It is clear, however, that the consequences of Alfvén transport are strongly model dependent and that both advection of cosmic rays by the waves and dissipation of wave energy in the plasma will be important to model correctly when quantitative results are needed. Comparison is made between simulations based on a constant diffusion coefficient and more realistic diffusion models allowing the diffusion coefficient to vary in response to changes in Alfvén wave intensity. No really substantive differences were found between them.Subject headings: cosmic rays — MHD — shock waves
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46

Squire, Jonathan, Philip F. Hopkins, Eliot Quataert, and Philipp Kempski. "The impact of astrophysical dust grains on the confinement of cosmic rays." Monthly Notices of the Royal Astronomical Society 502, no. 2 (January 27, 2021): 2630–44. http://dx.doi.org/10.1093/mnras/stab179.

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ABSTRACT We argue that charged dust grains could significantly impact the confinement and transport of galactic cosmic rays. For sub-GeV to ∼103 GeV cosmic rays, small-scale parallel Alfvén waves, which isotropize cosmic rays through gyro-resonant interactions, are also gyro-resonant with charged grains. If the dust is nearly stationary, as in the bulk of the interstellar medium, Alfvén waves are damped by dust. This will reduce the amplitude of Alfvén waves produced by the cosmic rays through the streaming instability, thus enhancing cosmic ray transport. In well-ionized regions, the dust damping rate is larger by a factor of ∼10 than other mechanisms that damp parallel Alfvén waves at the scales relevant for ∼GeV cosmic rays, suggesting that dust could play a key role in regulating cosmic ray transport. In astrophysical situations in which the dust moves through the gas with super-Alfvénic velocities, Alfvén waves are rendered unstable, which could directly scatter cosmic rays. This interaction has the potential to create a strong feedback mechanism where dust, driven through the gas by radiation pressure, then strongly enhances the confinement of cosmic rays, increasing their capacity to drive outflows. This mechanism may act in the circumgalactic medium around star-forming galaxies and active galactic nuclei.
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47

Chan, T. K., D. Kereš, P. F. Hopkins, E. Quataert, K.-Y. Su, C. C. Hayward, and C.-A. Faucher-Giguère. "Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV γ-ray emission." Monthly Notices of the Royal Astronomical Society 488, no. 3 (July 10, 2019): 3716–44. http://dx.doi.org/10.1093/mnras/stz1895.

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ABSTRACT We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-L⋆ starburst, and L⋆ galaxies with different propagation models, including advection, isotropic, and anisotropic diffusion, and streaming along field lines with different transport coefficients. We simulate CR diffusion and streaming simultaneously in galaxies with high resolution, using a two-moment method. We forward-model and compare to observations of γ-ray emission from nearby and starburst galaxies. We reproduce the γ-ray observations of dwarf and L⋆ galaxies with constant isotropic diffusion coefficient $\kappa \sim 3\times 10^{29}\, {\rm cm^{2}\, s^{-1}}$. Advection-only and streaming-only models produce order of magnitude too large γ-ray luminosities in dwarf and L⋆ galaxies. We show that in models that match the γ-ray observations, most CRs escape low-gas-density galaxies (e.g. dwarfs) before significant collisional losses, while starburst galaxies are CR proton calorimeters. While adiabatic losses can be significant, they occur only after CRs escape galaxies, so they are only of secondary importance for γ-ray emissivities. Models where CRs are ‘trapped’ in the star-forming disc have lower star formation efficiency, but these models are ruled out by γ-ray observations. For models with constant κ that match the γ-ray observations, CRs form extended haloes with scale heights of several kpc to several tens of kpc.
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48

Thomas, T., and C. Pfrommer. "Comparing different closure relations for cosmic ray hydrodynamics." Monthly Notices of the Royal Astronomical Society 509, no. 4 (October 25, 2021): 4803–16. http://dx.doi.org/10.1093/mnras/stab3079.

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ABSTRACT Cosmic ray (CR) hydrodynamics is a (re-)emerging field of high interest due to the importance of CRs for the dynamical evolution of the interstellar, the circumgalactic, and the intracluster medium. In these environments, CRs with GeV energies can influence large-scale dynamics by regulating star formation, driving galactic winds, or altering the pressure balance of galactic haloes. Recent efforts have moved the focus of the community from a one-moment description of CR transport towards a two-moment model as this allows for a more accurate description of the microphysics impacting the CR population. Like all hydrodynamical theories, these two-moment methods require a closure relation for a consistent and closed set of evolution equations. The goal of this paper is to quantify the impact of different closure relations on the resulting solutions. To this end, we review the common P1 and M1 closure relations, derive a new four-moment H1 description for CR transport, and describe how to incorporate CR scattering by Alfvén waves into these three hydrodynamical models. While there are significant differences in the transport properties of radiation in the P1 and M1 approximations in comparison to more accurate radiative transfer simulations using the discrete ordinates approximation, we only find small differences between the three hydrodynamical CR transport models in the free-streaming limit when we neglect CR scattering. Most importantly, for realistic applications in the interstellar, circumgalactic, or intracluster medium where CR scattering is frequent, these differences vanish and all presented hydrodynamical models produce the same results.
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49

Exarhos, G., and X. Moussas. "On the heliolatitudinal variation of the galactic cosmic-ray intensity. Comparison with Ulysses measurements." Annales Geophysicae 21, no. 6 (June 30, 2003): 1341–45. http://dx.doi.org/10.5194/angeo-21-1341-2003.

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Abstract. We study the dependence of cosmic rays with heliolatitude using a simple method and compare the results with the actual data from Ulysses and IMP spacecraft. We reproduce the galactic cosmic-ray heliographic latitudinal intensity variations, applying a semi-empirical, 2-D diffusion-convection model for the cosmic-ray transport in the interplanetary space. This model is a modification of our previous 1-D model (Exarhos and Moussas, 2001) and includes not only the radial diffusion of the cosmic-ray particles but also the latitudinal diffusion. Dividing the interplanetary region into "spherical magnetic sectors" (a small heliolatitudinal extension of a spherical magnetized solar wind plasma shell) that travel into the interplanetary space at the solar wind velocity, we calculate the cosmic-ray intensity for different heliographic latitudes as a series of successive intensity drops that all these "spherical magnetic sectors" between the Sun and the heliospheric termination shock cause the unmodulated galactic cosmic-ray intensity. Our results are compared with the Ulysses cosmic-ray measurements obtained during the first pole-to-pole passage from mid-1994 to mid-1995.Key words. Interplanetary physics (cosmic rays; interplanetray magnetic fields; solar wind plasma)
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50

Schlickeiser, Reinhard, and Ulrich Achat. "Cosmic-ray particle transport in weakly turbulent plasmas. Part 2. Mean free path of cosmic-ray protons." Journal of Plasma Physics 50, no. 1 (August 1993): 85–107. http://dx.doi.org/10.1017/s0022377800026933.

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We use the general Fokker–Planck coefficients derived in the first paper of this series, which describe the interaction of energetic charged particles with weak plasma turbulence in a magnetized plasma, to calculate the mean free path λ of cosmic-ray particles along the uniform background magnetic field. This quantity is a key parameter for confining energetic charged particles in cosmic plasmas, and can be experimentally inferred from interplanetary in-situ observations of solar particle events
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