Reconciling cosmic ray diffusion with Galactic magnetic field models

Giacinti, Gwenael; Kachelrieß, M.; Semikoz, D.

doi:10.1088/1475-7516/2018/07/051

Cited by 70 publications

(66 citation statements)

References 90 publications

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“…If the number of contributing sources is reduced by a factor 100 as argued in Ref. [150], only few sources may be responsible for the locally observed CR flux above 200 GeV. In this scenario, one expects also at lower energies a reduced number of sources contributing which should manifest itself by additional small breaks in the primary spectra.…”

Section: Discussionmentioning

confidence: 85%

“…In Refs. [93,150], it was found that L 0 L c /(2π) provides a good fit to their numerical results. The presence of the factor 1/(2π) becomes evident recalling that we compare in Eq.…”

Section: Sources Of Crsmentioning

confidence: 91%

“…These observational anomalies and ideas for their solutions will be described in the next two subsections. Before that we will discuss a more conceptional challenge for the approximations employed in the standard diffusion approach [150].…”

Section: Sources Of Crsmentioning

confidence: 99%

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Cosmic ray models

Kachelrieß

Semikoz

2019

Progress in Particle and Nuclear Physics

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We review progress in high-energy cosmic ray physics focusing on recent experimental results and models developed for their interpretation. Emphasis is put on the propagation of charged cosmic rays, covering the whole range from ∼ (20 − 50) GV, i.e. the rigidity when solar modulations can be neglected, up to the highest energies observed. We discuss models aiming to explain the anomalies in Galactic cosmic rays, the knee, and the transition from Galactic to extragalactic cosmic rays.

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Section: Discussionmentioning

confidence: 85%

“…In Refs. [93,150], it was found that L 0 L c /(2π) provides a good fit to their numerical results. The presence of the factor 1/(2π) becomes evident recalling that we compare in Eq.…”

Section: Sources Of Crsmentioning

confidence: 91%

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Cosmic ray models

Kachelrieß

Semikoz

2019

Progress in Particle and Nuclear Physics

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“…Moreover, some of the simulations above did not incorporate potentially-critical CR physics: ignoring CR losses (so CRs have essentially "infinite" energy/cooling times), treating only CR streaming or diffusion, ignoring magnetic fields (which can confine the CRs and regulate their transport), or (for numerical timestep reasons) using artificially low CR diffusion coefficients 2 κ 10 29 cm 2 s −1 , which artificially confines CRs near galaxies (generating stronger effects there) but violates observational constraints from spallation in the MW and γ-ray emission in nearby galaxies (see Lacki et al 2011;Cummings et al 2016;Jóhannesson et al 2016;Korsmeier & Cuoco 2016;Guo et al 2016;Fu et al 2017;Lopez et al 2018;Chan et al 2018;Giacinti et al 2018). It is therefore critical to study the effects of CRs in fully-cosmological simulations, which attempt to directly treat the multi-phase ISM and mechanical/radiative (i.e.…”

Section: Introductionmentioning

confidence: 99%

Cosmic ray driven outflows to Mpc scales from L* galaxies

Hopkins

Chan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (Mhalo ≳ 1011 M⊙), low-redshift (z ≲ 1 − 2) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive halos “traps” galactic outflows near the disk, so they recycle. With CRs injected in supernovae as modeled here, the low-pressure halo allows “escape” and CR pressure gradients continuously accelerate this material well into the IGM in “fast” outflows, while lower-density gas at large radii is accelerated in-situ into “slow” outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disk to >Mpc. The CR-driven outflows are primarily cool (T ∼ 105 K) and low-velocity. All of these effects weaken and eventually vanish at lower halo masses (≲ 1011 M⊙) or higher redshifts (z ≳ 1 − 2), reflecting the ratio of CR to thermal+gravitational pressure in the outer halo. We present a simple analytic model which explains all of the above phenomena. We caution that these predictions may depend on uncertain CR transport physics.

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“…To distinguish them from DM explanation is certainly important task [28] and it is in progress. Also specifics of possible anisotropy of CR propagation in galactic magnetic fields [29,30] may effectively shorten CR travelling length. So CR puzzles could be explained [31][32][33]…”

Section: Introductionmentioning

confidence: 99%

Development of dark disk model of positron anomaly origin

Belotskiy

Кириллов

Solovyov

2018

Int. J. Mod. Phys. D

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Dark disk model could be a remedy for dark matter (DM) explanation of positron anomaly (PA) in cosmic rays (CR). The main difficulty in PA explanation relates to cosmic gamma-radiation which is inevitably produced in DM annihilation or decay leading to tension with respective observation data. Introduction of "active" (producing CR) DM component concentrating in galactic disk alleviates this tension. Earlier we considered two-lepton modes, with branching ratios being chosen to fit in the best way all the observation data. Here we considered, in framework of the same dark disk model, two cases: two-body final state annihilation and four-body one, and in each case a quark mode is added to the leptonic ones. It is shown that 4-body mode case is a little better than 2-body one from viewpoint of quality of observation data description at the fixed all other parameters (of CR propagation, background, disk height). The values of DM particle mass around 350 GeV and 500 GeV are more favourable for 2-and 4-body modes respectively. Higher values would improve description of data on positrons only but accounting for data on gamma-radiation prevents it because of unwanted more abundant high-energy gamma production. Inclusion of the quark modes improves a little fitting data in both 4-and 2-body mode cases, contrary to naive expectations. In fact, quark mode has a bigger gammas yield than that of most gamma-productive leptonic mode -tau, but they are softer due to bigger final state hadron multiplicity.

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Reconciling cosmic ray diffusion with Galactic magnetic field models

Cited by 70 publications

References 90 publications

Cosmic ray models

Cosmic ray models

Cosmic ray driven outflows to Mpc scales from L* galaxies

Development of dark disk model of positron anomaly origin

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