Relaxation of heavy ions in collisionless shock waves in cosmic plasma

Kropotina, Yu. A.; Bykov, A. M.; Krasil’shchikov, A. M.; Levenfish, K. P.

doi:10.1134/s1063784216040149

Cited by 14 publications

(7 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The hybrid codes (see e.g. Quest, 1988;Winske and Omidi, 1996;Giacalone et al, 1997;Lipatov, 2002;Gargaté et al, 2007;Caprioli and Spitkovsky, 2014;Kropotina et al, 2016) are widely used for modeling of collisionless shocks. We discuss in § 3.1 the effect of He ions on the shock injection process and the shape of He and Fe ion distributions at the collisionless shocks in high β ICM plasma.…”

Section: Plasma Physics Of the Long-wavelength Motions In Clusters Ofmentioning

confidence: 99%

Shocks and Non-thermal Particles in Clusters of Galaxies

et al. 2019

Self Cite

View full text Add to dashboard Cite

Galaxy clusters grow by gas accretion, mostly from mergers of substructures, which release powerful shock waves into cosmic plasmas and convert a fraction of kinetic energy into thermal energy, amplification of magnetic fields and into the acceleration of energetic particles. The modeling of the radio signature of cosmic shocks, combined with the lack of detected γ-rays from cosmic ray (CR) protons, poses challenges to our understanding of how cosmic rays get accelerated and stored in the intracluster medium. Here we review the injection of CRs by cosmic shocks of different strengths, combining the detailed "microscopic" view of collisionless processes governing the creation of non-thermal distributions of electrons and protons in cluster shocks (based on analytic theory and particle-in-cell simulations), with the "macroscopic" view of the large-scale distribution of cosmic rays, suggested by modern cosmological simulations. Time dependent non-linear kinetic models of particle acceleration by multiple internal shocks with large scale compressible motions of plasma with soft CR spectra containing a noticable energy density in the superthermal protons of energies below a few GeV which is difficult to constrain by Fermi

show abstract

Section: Plasma Physics Of the Long-wavelength Motions In Clusters Ofmentioning

confidence: 99%

Shocks and Non-thermal Particles in Clusters of Galaxies

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hybrid simulations of non-relativistic shocks have been extensively used for assessing the efficiency of proton DSA [13], the generation of magnetic turbulence due to plasma instabilities driven by accelerated particles [15], the diffusion of energetic particles in such self-generated magnetic fields [16], and the injection of protons into the DSA process [17]. In the literature there are few examples of kinetic simulations with heavy ions, e.g., the pioneering 1D hybrid simulations of weak shocks including α−particles [18,19] and the recent hybrid study of the thermalization of weakly-charged ions at shocks [20]. However, a selfconsistent kinetic characterization of ion enhancement in DSA has never been performed before [see, e.g, 8, 21, for Monte Carlo and semi-analytical approaches].…”

mentioning

confidence: 99%

Chemical Enhancements in Shock-Accelerated Particles: Ab initio Simulations

Caprioli

Spitkovsky

2017

Phys. Rev. Lett.

View full text Add to dashboard Cite

We study the thermalization, injection, and acceleration of ions with different mass/charge ratios, A/Z, in non-relativistic collisionless shocks via hybrid (kinetic ions-fluid electrons) simulations. In general, ions thermalize to a post-shock temperature proportional to A. When diffusive shock acceleration is efficient, ions develop a non-thermal tail whose extent scales with Z and whose normalization is enhanced as (A/Z) 2 , so that incompletely-ionized heavy ions are preferentially accelerated. We discuss how these findings can explain observed heavy-ion enhancements in Galactic cosmic rays. PACS numbers:Introduction.-Non-relativistic shocks are well-known as sources of energetic particles. Prominent examples of such shocks are the blast waves of supernova remnants (SNRs), which are thought to be the sources of Galactic cosmic rays (GCRs) [e.g., 1, 2], and heliospheric shocks, where solar energetic particles (SEPs) are measured in situ [e.g., 3, 4]. Chemical abundances in GCRs and SEPs provide crucial information about their sources and the processes responsible for their acceleration.At trans-relativistic energies, the chemical composition of GCRs roughly resembles the composition of the solar system [5], the most evident deviation being the enhancement of secondaries produced by spallation of primary GCRs during their propagation in the Milky Way. A more careful analysis, however, reveals that the GCR composition is controlled by volatility and mass/charge ratios: refractory elements show larger enhancements than volatile ones, and heavier volatile elements are more abundant than lighter ones [6,7]. Moreover, elemetns with low first ionization potential tend to be overrepresented in GCRs [e.g.,5]. At TeV energies, where spallation is negligible, the fluxes of H, He, C-N-O, and Fe do not differ by more than one order of magnitude [e.g., 8, and references therein]. Since their typical solar number abundances relative to H are χ He = 0.0963, χ CN O = 9.54 × 10 −4 , χ F e = 8.31 × 10 −5 [9], the abundances observed in GCRs suggest that heavy ions must be preferentially injected and accelerated compared to protons.Diffusive shock acceleration (DSA) [e.g., 10, 11] at SNR shocks is likely the mechanism responsible for ion acceleration up to ∼ 10 17 eV [12]. DSA produces universal power-law momentum spectra f (p) ∝ p −3r/(r−1) , where r is the shock compression ratio; for strong shocks r → 4 and f (p) ∝ p −4 . For relativistic particles the energy spectrum is then f (E) = 4πp 2 f (p)dp/dE ∝ E −2 , while at non-relativistic energies one gets f (E) ∝ E −3/2 [13].

show abstract

“…dHybridR is the generalization of the Newtonian code dHybrid (Gargaté et al 2007), which has been already widely used for simulating collisionless shocks (Gargaté & Spitkovsky 2012;Caprioli & Spitkovsky 2014a,b,c;Caprioli et al , 2017Caprioli et al 2018;. Hybrid codes are better suited to self-consistently simulate the long-term shock evolution than full particle-in-cell codes because they do not need to resolve the small time/length scales of the electrons, which are usually dynamically negligible (see, e.g., Winske 1985;Quest 1988;Scholer 1990;Giacalone et al 1992Giacalone et al , 1993Bennett & Ellison 1995;Winske & Omidi 1996;Giacalone et al 1997;Giacalone & Ellison 2000;Giacalone 2004;Burgess et al 2005;Lipatov 2002;Guo & Giacalone 2013;Burgess et al 2016;Kropotina et al 2016;Hanusch et al 2019, and references therein).…”

Section: Hybrid Simulationsmentioning

confidence: 99%

Kinetic Simulations of Cosmic-Ray-Modified Shocks I: Hydrodynamics

Haggerty,

Caprioli

2020

Preprint

View full text Add to dashboard Cite

Collisionless plasma shocks are efficient sources of non-thermal particle acceleration in space and astrophysical systems. We use hybrid (kinetic ions -fluid electrons) simulations to examine the nonlinear feedback of the self-generated energetic particles (cosmic rays, CRs) on the shock hydrodynamics. When CR acceleration is efficient, we find evidence of both an upstream precursor, where the inflowing plasma is compressed and heated, and a downstream postcursor, where the energy flux in CRs and amplified magnetic fields play a dynamical role. For the first time, we assess how non-linear magnetic fluctuations in the postcursor preferentially travel away from the shock at roughly the local Alfvén speed with respect to the downstream plasma. The drift of both magnetic and CR energy with respect to the thermal plasma substantially increases the shock compression ratio with respect to the standard prediction, in particular exceeding 4 for strong shocks. Such modifications also have implications for the spectrum of the particles accelerated via diffusive shock acceleration, a significant result detailed in a companion paper, Caprioli et al.

show abstract

Relaxation of heavy ions in collisionless shock waves in cosmic plasma

Cited by 14 publications

References 32 publications

Shocks and Non-thermal Particles in Clusters of Galaxies

Shocks and Non-thermal Particles in Clusters of Galaxies

Chemical Enhancements in Shock-Accelerated Particles: Ab initio Simulations

Kinetic Simulations of Cosmic-Ray-Modified Shocks I: Hydrodynamics

Contact Info

Product

Resources

About