Spectrally resolved cosmic ray hydrodynamics – I. Spectral scheme

Girichidis, Philipp; Pfrommer, Christoph; Hanasz, M.; Naab, Thorsten

doi:10.1093/mnras/stz2961

Cited by 55 publications

(43 citation statements)

References 59 publications

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“…Recent results from Evoli et al (2018) show, in particular, that the turbulent cascade from CR sources and the selfgeneration of waves by CRs can introduce an effective halo size. Full numerical simulations aimed at accurately computing CRs in a magneto-hydrodynamic framework will probably give more insight into this problem, as envisaged in Girichidis et al (2020). In the meantime, the concept of hard boundary remains a useful benchmark for many CR-related studies.…”

Section: Introductionmentioning

confidence: 99%

Galactic halo size in the light of recent AMS-02 data

Weinrich

Boudaud

Derome

et al. 2020

A&A

130

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Context. The vertical diffusive halo size of the Galaxy, L, is a key parameter for dark matter indirect searches. It can be better determined thanks to recent AMS-02 data. Aims. We set constraints on L from Be/B and 10Be/Be data, and we performed a consistency check with positron data. We detail the dependence of Be/B and 10Be/Be on L and forecast on which energy range better data would be helpful for future L improvements. Methods. We used USINE V3.5 for the propagation of nuclei, and e+ were calculated with the pinching method. Results. The current AMS-02 Be/B (∼3% precision) and ACE-CRIS 10Be/Be (∼10% precision) data bring similar and consistent constraints on L. The AMS-02 Be/B data alone constrain L = 5−2+3 kpc at a 68% confidence level (spanning different benchmark transport configurations), a range for which most models do not overproduce positrons. Future experiments need to deliver percent-level accuracy on 10Be/9Be anywhere below 10 GV to further constrain L. Conclusions. Forthcoming AMS-02, HELIX, and PAMELA 10Be/9Be results will further test and possibly tighten the limits derived here. Elemental ratios involving radioactive species with different lifetimes (e.g. Al/Mg and Cl/Ar) are also awaited to provide complementary and robuster constraints.

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Section: Introductionmentioning

confidence: 99%

Galactic halo size in the light of recent AMS-02 data

Weinrich

Boudaud

Derome

et al. 2020

A&A

130

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“…The forces that couple CRs to the interstellar plasma can drive bulk motions in the latter -the so-called CR-driven galactic winds (Ipavich 1975;Breitschwerdt et al 1991;Everett et al 2008;Socrates et al 2008). Much attention has been given to this mechanism in recent years, both in large-scale fluid simulation studies (Girichidis et al 2016;Wiener et al 2017;Ruszkowski et al 2017b;Girichidis et al 2018;Jiang & Oh 2018;Thomas & Pfrommer 2019), and in analytical fluid studies (Recchia et al 2016;Mao & Ostriker 2018).…”

Section: Introductionmentioning

confidence: 99%

On the Growth and Saturation of the Gyroresonant Streaming Instabilities

Holcomb

Spitkovsky

2019

ApJ

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The self-regulation of cosmic ray (CR) transport in the interstellar and intracluster media has long been viewed through the lenses of linear and quasilinear kinetic plasma physics. Such theories are believed to capture the essence of CR behavior in the presence of self-generated turbulence, but cannot describe potentially critical details arising from the nonlinearities of the problem. We utilize the particle-in-cell numerical method to study the time-dependent nonlinear behavior of the gyroresonant streaming instabilities, self-consistently following the combined evolution of particle distributions and self-generated wave spectra in one-dimensional periodic simulations. We demonstrate that the early growth of instability conforms to the predictions from linear physics, but that the late-time behavior can vary depending on the properties of the initial CR distribution. We emphasize that the nonlinear stages of instability depend strongly on the initial anisotropy of CRs -highly anisotropic CR distributions do not efficiently reduce to Alfvénic drift velocities, owing to reduced production of left-handed resonant modes. We derive estimates for the wave amplitudes at saturation and the time scales for nonlinear relaxation of the CR distribution, then demonstrate the applicability of these estimates to our simulations. Bulk flows of the background plasma due to the presence of resonant waves are observed in our simulations, confirming the microphysical basis of CR-driven winds.

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“…The modeling of steady-state CR proton and electron spectra in 3D MHD simulations enabled us to gain new insights into the underlying physical processes that are responsible for the observed relations between non-thermal radio and gamma-ray emission with tracers of SF in galaxies. Possible improvements of this model would be cosmological simulations in order to obtain a more realistic SF history, as well as the inclusion of full spectral-dynamical simulations of CRs [18,19]. Furthermore, future improvements of the ISM model might enable us to resolve the turbulence induced by SF, potentially yielding a stronger magnetic small-scale dynamo.…”

Section: Discussionmentioning

confidence: 99%

Simulating cosmic rays and the gamma-ray emission in star-forming galaxies

Werhahn¹,

Pfrommer²,

Girichidis³

2021

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

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Previously, the non-thermal emission from galaxies has only been modeled with single-zone models which is insufficient to explain a multitude of new, spatially resolved multi-messenger data of cosmic ray (CR) spectra, at gamma-rays and in the radio. Instead, we perform high-resolution magneto-hydrodynamic simulations of galaxies using the moving mesh code AREPO with selfconsistent CR physics. In post-processing, we calculate steady-state spectra of CRs including all relevant cooling and escape losses. Consistent with Voyager-1 and AMS-02 data, our models show a turn-over of proton spectra below GeV energies due to Coulomb interactions so that electrons start to dominate the total particle spectra and match the shape of the positron fraction up to 10 GeV. Furthermore, from our CR spectra, we calculate multi-frequency spectra, from the radio up to the TeV energy regime, due to all non-thermal emission processes, i.e. synchrotron, bremsstrahlung, inverse Compton (IC) emission and gamma-ray emission from neutral pion decay. This allows us to produce detailed emission maps, luminosities and spectra of our simulated galaxies, that range from dwarfs to Milk-Way analogues to starburst galaxies, at different evolutionary stages. Within our simulations, we can successfully reproduce the observed far infrared (FIR)-gamma-ray and FIR-radio relations. We find that highly SF galaxies are close to the calorimetric limit and hence, their gamma-ray emission is dominated by neutral pion decay. However, in low SF galaxies, escape losses due to diffusion steepen the spectra and in turn, an increasing contribution from IC emission is needed to reproduce the observed gamma-ray spectra.

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Spectrally resolved cosmic ray hydrodynamics – I. Spectral scheme

Cited by 55 publications

References 59 publications

Galactic halo size in the light of recent AMS-02 data

Galactic halo size in the light of recent AMS-02 data

On the Growth and Saturation of the Gyroresonant Streaming Instabilities

Simulating cosmic rays and the gamma-ray emission in star-forming galaxies

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