scholarly journals Particle acceleration in the superwinds of starburst galaxies

2018 ◽  
Vol 616 ◽  
pp. A57 ◽  
Author(s):  
G. E. Romero ◽  
A. L. Müller ◽  
M. Roth
Keyword(s):  
Cosmic Rays ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
High Energy ◽  
Shock Acceleration ◽  
Spectral Energy ◽  
Starburst Galaxy ◽  
Diffusive Shock Acceleration ◽  
Mass Load ◽  
The Galaxy

Context. Starbursts are galaxies undergoing massive episodes of star formation. The combined effect of stellar winds from hot stars and supernova explosions creates a high-temperature cavity in the nuclear region of these objects. The very hot gas expands adiabatically and escapes from the galaxy creating a superwind which sweeps matter from the galactic disk. The superwind region in the halo is filled with a multi-phase gas with hot, warm, cool, and relativistic components. Aims. The shocks associated with the superwind of starbursts and the turbulent gas region of the bubble inflated by them might accelerate cosmic rays up to high energies. In this work we calculate the cosmic ray production associated with the superwind using parameters that correspond to the nearby southern starburst galaxy NGC 253, which has been suggested as a potential accelerator of ultra-high-energy cosmic rays. Methods. We evaluate the efficiency of both diffusive shock acceleration (DSA) and stochastic diffusive acceleration (SDA) in the superwind of NGC 253. We estimate the distribution of both hadrons and leptons and calculate the corresponding spectral energy distributions of photons. The electromagnetic radiation can help to discriminate between the different scenarios analyzed. Results. We find that the strong mass load of the superwind, recently determined through ALMA observations, strongly attenuates the efficiency of DSA in NGC 253, whereas SDA is constrained by the age of the starburst. Conclusions. We conclude that NGC 253 and similar starbursts can only accelerate iron nuclei beyond ~1018 eV under very special conditions. If the central region of the galaxy harbors a starved supermassive black hole of ~106 M⊙, as suggested by some recent observations, a contribution in the range 1018−1019 eV can be present for accretion rates ṁ ~ 10−3 in Eddington units. Shock energies of the order of 100 EeV might only be possible if very strong magnetic field amplification occurs close to the superwind.

scholarly journals Cosmic rays and stochastic magnetic reconnection in the heliotail

2012 ◽  
Vol 19 (3) ◽  
pp. 351-364 ◽  
Author(s):  
P. Desiati ◽  
A. Lazarian
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Magnetic Reconnection ◽  
Supernova Remnants ◽  
Average Energy ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
The Galaxy

Abstract. Galactic cosmic rays are believed to be generated by diffusive shock acceleration processes in Supernova Remnants, and the arrival direction is likely determined by the distribution of their sources throughout the Galaxy, in particular by the nearest and youngest ones. Transport to Earth through the interstellar medium is expected to affect the cosmic ray properties as well. However, the observed anisotropy of TeV cosmic rays and its energy dependence cannot be explained with diffusion models of particle propagation in the Galaxy. Within a distance of a few parsec, diffusion regime is not valid and particles with energy below about 100 TeV must be influenced by the heliosphere and its elongated tail. The observation of a highly significant localized excess region of cosmic rays from the apparent direction of the downstream interstellar flow at 1–10 TeV energies might provide the first experimental evidence that the heliotail can affect the transport of energetic particles. In particular, TeV cosmic rays propagating through the heliotail interact with the 100–300 AU wide magnetic field polarity domains generated by the 11 yr cycles. Since the strength of non-linear convective processes is expected to be larger than viscous damping, the plasma in the heliotail is turbulent. Where magnetic field domains converge on each other due to solar wind gradient, stochastic magnetic reconnection likely occurs. Such processes may be efficient enough to re-accelerate a fraction of TeV particles as long as scattering processes are not strong. Therefore, the fractional excess of TeV cosmic rays from the narrow region toward the heliotail direction traces sightlines with the lowest smearing scattering effects, that can also explain the observation of a harder than average energy spectrum.

scholarly journals Composition and Galactic Confinement of Cosmic Rays

1971 ◽  
Vol 2 ◽  
pp. 740-756
Author(s):  
Maurice M. Shapiro
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Interstellar Space ◽  
Heavy Nuclei ◽  
High Energy Astrophysics ◽  
Transit Times ◽  
The Galaxy ◽  
Path Lengths

The ‘Galactic’ cosmic rays impinging on the Earth come from afar over tortuous paths, traveling for millions of years. These particles are the only known samples of matter that reach us from regions of space beyond the solar system. Their chemical and isotopic composition and their energy spectra provide clues to the nature of cosmic-ray sources, the properties of interstellar space, and the dynamics of the Galaxy. Various processes in high-energy astrophysics could be illuminated by a more complete understanding of the arriving cosmic rays, including the electrons and gamma rays.En route, some of theprimordialcosmic-ray nuclei have been transformed by collision with interstellar matter, and the composition is substantially modified by these collisions. A dramatic consequence of the transformations is the presence in the arriving ‘beam’ of considerable fluxes of purely secondary elements (Li, Be, B), i.e., species that are, in all probability, essentially absent at the sources. We shall here discuss mainly the composition of the arriving ‘heavy’ nuclei -those heavier than helium - and what they teach us about thesourcecomposition, the galactic confinement of the particles, their path lengths, and their transit times.

scholarly journals The Origin of the Most Energetic Galactic Cosmic Rays: Supernova Explosions into Massive Star Plasma Winds

Galaxies ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 48 ◽  
Author(s):  
Peter L. Biermann ◽  
Philipp P. Kronberg ◽  
Michael L. Allen ◽  
Athina Meli ◽  
Eun-Suk Seo
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Space Station ◽  
Cosmic Ray ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Starburst Galaxy ◽  
Supergiant Star

We propose that the high energy Cosmic Ray particles up to the upturn commonly called the ankle, from around the spectral turn-down commonly called the knee, mostly come from Blue Supergiant star explosions. At the upturn, i.e., the ankle, Cosmic Rays probably switch to another source class, most likely extragalactic sources. To show this we recently compiled a set of Radio Supernova data where we compute the magnetic field, shock speed and shock radius. This list included both Blue and Red Supergiant star explosions; both data show the same magnetic field strength for these two classes of stars despite very different wind densities and velocities. Using particle acceleration theory at shocks, those numbers can be transformed into characteristic ankle and knee energies. Without adjusting any free parameters both of these observed energies are directly indicated by the supernova data. In the next step in the argument, we use the Supernova Remnant data of the starburst galaxy M82. We apply this analysis to Blue Supergiant star explosions: The shock will race to their outer edge with a magnetic field that is observed to follow over several orders of magnitude B ( r ) × r ∼ c o n s t . , with in fact the same magnetic field strength for such stellar explosions in our Galaxy, and other galaxies including M82. The speed is observed to be ∼0.1 c out to about 10 16 cm radius in the plasma wind. The Supernova shock can run through the entire magnetic plasma wind region at full speed all the way out to the wind-shell, which is of order parsec scale in M82. We compare and identify the Cosmic Ray spectrum in other galaxies, in the starburst galaxy M82 and in our Galaxy with each other; we suggest how Blue Supergiant star explosions can provide the Cosmic Ray particles across the knee and up to the ankle energy range. The data from the ISS-CREAM (Cosmic Ray Energetics and Mass Experiment at the International Space Station) mission will test this cosmic ray concept which is reasonably well grounded in two independent radio supernova data sets. The next step in developing our understanding will be to obtain future more accurate Cosmic Ray data near to the knee, and to use unstable isotopes of Cosmic Ray nuclei at high energy to probe the “piston” driving the explosion. We plan to incorporate these data with the physics of the budding black hole which is probably forming in each of these stars.

scholarly journals Particle acceleration in winds of star clusters

2021 ◽  
Author(s):  
G Morlino ◽  
P Blasi ◽  
E Peretti ◽  
P Cristofari
Keyword(s):  
Particle Acceleration ◽  
Cosmic Rays ◽  
Supernova Remnants ◽  
Star Clusters ◽  
Cosmic Ray ◽  
Maximum Energy ◽  
Termination Shock ◽  
Shock Acceleration ◽  
Acceleration Process ◽  
Diffusive Shock Acceleration

Abstract The origin of cosmic rays in our Galaxy remains a subject of active debate. While supernova remnant shocks are often invoked as the sites of acceleration, it is now widely accepted that the difficulties of such sources in reaching PeV energies are daunting and it seems likely that only a subclass of rare remnants can satisfy the necessary conditions. Moreover the spectra of cosmic rays escaping the remnants have a complex shape that is not obviously the same as the spectra observed at the Earth. Here we investigate the process of particle acceleration at the termination shock that develops in the bubble excavated by star clusters’ winds in the interstellar medium. While the main limitation to the maximum energy in supernova remnants comes from the need for effective wave excitation upstream so as to confine particles in the near-shock region and speed up the acceleration process, at the termination shock of star clusters the confinement of particles upstream in guaranteed by the geometry of the problem. We develop a theory of diffusive shock acceleration at such shock and we find that the maximum energy may reach the PeV region for powerful clusters in the high end of the luminosity tail for these sources. A crucial role in this problem is played by the dissipation of energy in the wind to magnetic perturbations. Under reasonable conditions the spectrum of the accelerated particles has a power law shape with a slope 4÷4.3, in agreement with what is required based upon standard models of cosmic ray transport in the Galaxy.

scholarly journals Spectral and Polarization Signatures of Relativistic Shocks in Blazars

2016 ◽  
Author(s):  
Markus Boettcher
Keyword(s):  
Pitch Angle ◽  
High Energy ◽  
Shock Acceleration ◽  
Spectral Energy ◽  
Polarization Angle ◽  
Proton Synchrotron ◽  
Diffusive Shock Acceleration ◽  
X Ray ◽  
Relativistic Shocks ◽  
Multi Wavelength

Relativistic shocks are one of the most plausible sites of the emission of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars, via diffusive shock acceleration (DSA) of relativistic particles. This paper summarizes recent results on a self-consistent coupling of diffusive shock acceleration and radiation transfer in blazar jets. We demonstrate that the observed spectral energy distributions (SEDs) of blazars strongly constrain the nature of hydromagnetic turbulence responsible for pitch-angle scattering by requiring a strongly energy-dependent pitch-angle mean free path. The prominent soft X-ray excess (``Big Blue Bump'') in the SED of the BL Lac object AO 0235+164 can be modelled as the signature of bulk Compton scattering of external radiation fields by the thermal electron population, which places additional constraints on the level of hydromagnetic turbulence. It has further been demonstrated that internal shocks propagating in a jet pervaded by a helical magnetic field naturally produce polarization-angle swings by 180$^o$, in tandem with multi-wavelength flaring activity, without requiring any helical motion paths or other asymmetric jet structures. The specific application of this model to 3C279 presents the first consistent, simultaneous modeling of snap-shot SEDs, multi-wavelength light curves and time-dependent polarization signatures of a blazar during a polarization-angle (PA) rotation. This model has recently been generalized to a lepto-hadronic model, in which the high-energy emission is dominated by proton synchrotron radiation. It is shown that in this case, the high-energy (X-ray and $\gamma$-ray) polarization signatures are expected to be significantly more stable (not showing PA rotations) than the low-energy (electron-synchrotron) signatures.

scholarly journals Bohm Diffusion and Cosmic-Ray-Modified Shocks

1994 ◽  
Vol 142 ◽  
pp. 981-983
Author(s):  
Peter Duffy
Keyword(s):  
Particle Acceleration ◽  
Cosmic Rays ◽  
Cosmic Ray ◽  
Shock Acceleration ◽  
Back Reaction ◽  
Acceleration Of Particles ◽  
Diffusive Shock Acceleration ◽  
Spacetime Structure ◽  
Wide Range ◽  
Self Consistent

AbstractA numerical solution to the problem of self-consistent diffusive shock acceleration is presented. The cosmic rays are scattered, accelerated and exert a back-reaction on the gas through their interaction with turbulence frozen into the local fluid frame. Using a grid with a hierarchical spacetime structure the physically interesting limit of Bohm diffusion (к ∝ pv), which introduces a wide range of diffusion lengthscales and acceleration timescales, can be studied. Some implications for modified shocks and particle acceleration are presented.Subject headings: acceleration of particles — cosmic rays — diffusion — shock waves

scholarly journals Manufacturing cosmic rays in the evolving dynamical states of galaxy clusters

2019 ◽  
Vol 488 (1) ◽  
pp. 1301-1319 ◽  
Author(s):  
Reju Sam John ◽  
Surajit Paul ◽  
Luigi Iapichino ◽  
Karl Mannheim ◽  
Harish Kumar
Keyword(s):  
Cosmic Rays ◽  
Galaxy Clusters ◽  
Theoretical Calculations ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
X Ray ◽  
Mass Scaling ◽  
Dynamical Phase ◽  
The Galaxy ◽  
High Mach

ABSTRACT Galaxy clusters are known to be reservoirs of cosmic rays (CRs), as inferred from theoretical calculations or detection of CR-derived observables. CR acceleration in clusters is mostly attributed to the dynamical activity that produces shocks. Shocks in clusters emerge out of merger or accretion, but which one is more effective in producing CRs? at which dynamical phase? and why? To this aim, we study the production or injection of CRs through shocks and its evolution in the galaxy clusters using cosmological simulations with the enzo code. Particle acceleration model considered here is primarily the Diffusive Shock Acceleration (DSA) of thermal particles, but we also report a tentative study with pre-existing CRs. Defining appropriate dynamical states using the concept of virialization, we studied a sample of merging and non-merging clusters. We report that the merger shocks (with Mach number $\mathcal {M}\sim 2-5$) are the most effective CR producers, while high-Mach peripheral shocks (i.e. $\mathcal {M}\gt 5$) are mainly responsible for the brightest phase of CR injection in clusters. Clusters once merged, permanently deviate from CR and X-ray mass scaling of non-merging systems, enabling us to use it as a tool to determine the state of merger. Through a temporal and spatial evolution study, we found a strong correlation between cluster merger dynamics and CR injection. We observed that the brightest phase of X-ray and CR injection from clusters occurs, respectively, at about 1.0 and 1.5 Gyr after every mergers, and CR injection peaks near to the cluster virial radius (i.e r200). Delayed CR injection peaks found in this study deserve further investigation for possible impact on the evolution of CR-derived observables from galaxy clusters.

scholarly journals Contribution of the Galactic centre to the local cosmic-ray flux

2018 ◽  
Vol 619 ◽  
pp. A12 ◽  
Author(s):  
Étienne Jaupart ◽  
Étienne Parizot ◽  
Denis Allard
Keyword(s):  
Galactic Disk ◽  
A Priori ◽  
Cosmic Ray ◽  
High Energy ◽  
Single Type ◽  
Galactic Centre ◽  
High Energy Particle ◽  
The Galaxy ◽  
Injection Power ◽  
Galactic Cosmic Ray

Context. Recent observations of unexpected structures in the Galactic cosmic ray (GCR) spectrum and composition, as well as growing evidence for episodes of intense dynamical activity in the inner regions of the Galaxy, call for an evaluation of the high-energy particle acceleration associated with such activity and its potential impact on the global GCR phenomenology. Aims. We investigate whether particles accelerated during high-power episodes around the Galactic centre can account for a significant fraction of the observed GCRs, or, conversely, what constraints can be derived regarding their Galactic transport if their contributions are negligible. Methods. Particle transport in the Galaxy is described with a two-zone analytical model. We solved for the contribution of a Galactic centre cosmic-Ray (GCCR) source using Green functions and Bessel expansion, and discussed the required injection power for these GCCRs to influence the global GCR phenomenology at Earth. Results. We find that, with standard parameters for particle propagation in the galactic disk and halo, the GCCRs can make a significant or even dominant contribution to the total CR flux observed at Earth. Depending on the parameters, such a source can account for both the observed proton flux and boron-to-carbon ratio (in the case of a Kraichnan-like scaling of the diffusion coefficient), or potentially produce spectral and composition features. Conclusions. Our results show that the contribution of GCCRs cannot be neglected a priori, and that they can influence the global GCR phenomenology significantly, thereby calling for a reassessement of the standard inferences from a scenario where GCRs are entirely dominated by a single type of sources distributed throughout the Galactic disk.

scholarly journals DIFFUSIVE PROPAGATION OF HIGH ENERGY COSMIC RAYS IN GALAXY: EFFECT OF HALL DRIFT

2011 ◽  
Vol 26 (05) ◽  
pp. 911-923 ◽  
Author(s):  
HIDEYOSHI ARAKIDA ◽  
SHUICHI KURAMATA
Keyword(s):  
Cosmic Rays ◽  
Diffusion Tensor ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Propagation Model ◽  
High Energy Cosmic Rays ◽  
Semi Empirical ◽  
Symmetric Diffusion

We phenomenologically developed a propagation model of high energy galactic cosmic rays. We derived the analytical solutions by adopting the semi-empirical diffusion equation, proposed by Berezinskii et al. (1990) and the diffusion tensor proposed by Ptuskin et al. (1993). This model takes into account both the symmetric diffusion and the antisymmetric diffusion due to the particle Hall drift. Our solutions are an extension of the model developed by Ptuskin et al. to a two-dimensional two-layer (galactic disk and halo) model, and they coincide completely with the solution derived by Berezinskii et al. in the absence of antisymmetric diffusion due to Hall drift. We showed that this relatively simple toy model can be used to explain the variation in the exponent of the cosmic ray energy spectrum, γ, around the knee E ≈1015 eV .

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