scholarly journals Hybrid modeling of diffusive shock acceleration in collisionless shocks in multispecies plasma

2018 ◽  
pp. 373-378
Author(s):  
J. A. Kropotina ◽  
A. M. Bykov ◽  
V. E. Ermolina ◽  
S. M. Osipov ◽  
V. I. Romansky
Keyword(s):  
Heavy Ions ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Hydrogen Plasma ◽  
High Energy ◽  
Shock Acceleration ◽  
High Energy Particle ◽  
Diffusive Shock Acceleration ◽  
Particle Injection ◽  
Initial Flow

Diffusive shock acceleration (DSA) is a very efficient mechanism of high energy particle acceleration in heliosphere, supernova remnants, stellar winds and gamma-ray bursts. We present microscopic simulation of particle injection and diffusive shock acceleration which is performed with 3D divergence-conserving second-order accurate hybrid code "Maximus". Hydrogen plasma with admixture of various heavy ions is considered. The injection process is found to start through shock reflection for both hydrogen and heavier ions. However, the reflection process depends on charge-to-mass ratio. While hydrogen ions reflection appears at shock ramp and is governed by the cross-shock potential, the reflection of ions with greater A=Z proceeds deeper down-stream via gyration in perpendicular magnetic field component. The heavy ions appear to inject into the DSA preferentially, but this chemical enhancement saturates with growing A=Z. The protons injection efficiency is estimated within various approaches, and it is shown that about 20% of initial flow energy goes into accelerated particles.

scholarly journals Gamma-rays from reaccelerated particles at supernova remnant shocks

2019 ◽  
Vol 489 (1) ◽  
pp. 108-115 ◽  
Author(s):  
P Cristofari ◽  
P Blasi
Keyword(s):  
Gamma Rays ◽  
Supernova Remnants ◽  
Large Scale ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Shock Acceleration ◽  
X Rays ◽  
Diffusive Shock Acceleration ◽  
Particle In Cell ◽  
Large Scale Magnetic Field

ABSTRACT Diffusive shock acceleration is considered as the main mechanism for particle energization in supernova remnants, as well as in other classes of sources. The existence of some remnants that show a bilateral morphology in the X-rays and gamma-rays suggests that this process occurs with an efficiency that depends upon the inclination angle between the shock normal and the large-scale magnetic field in which the shock propagates. This interpretation is additionally supported by recent particle-in-cell simulations that show how ions are not injected if the shock is more oblique than ∼45°. These shocks provide an excellent test bench for the process of reacceleration at the same shock: non-thermal seed particles that are reached by the shock front are automatically injected and accelerated. This process was recently discussed as a possible reason for some anomalous behaviour of the spectra of secondary cosmic ray nuclei. Here, we discuss how gamma-ray observations of selected supernova remnants can provide us with precious information about this process and lead us to a better assessment of particle diffusive shock reacceleration for other observables in cosmic ray physics.

scholarly journals A Shock-in-Jet Synchrotron Mirror Model for Blazars

Physics ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 1112-1122
Author(s):  
Markus Böttcher
Keyword(s):  
Synchrotron Radiation ◽  
Gamma Ray ◽  
Low Frequency ◽  
High Energy ◽  
Shock Acceleration ◽  
Additional Parameter ◽  
Diffusive Shock Acceleration ◽  
Spectral Variability ◽  
Particle Distributions ◽  
Self Consistent

Reinhard Schlickeiser has made groundbreaking contributions to various aspects of blazar physics, including diffusive shock acceleration, the theory of synchrotron radiation, the production of gamma-rays through Compton scattering in various astrophysical sources, etc. This paper, describing the development of a self-consistent shock-in-jet model for blazars with a synchrotron mirror feature, is therefore an appropriate contribution to a Special Issue in honor of Reinhard Schlickeiser’s 70th birthday. The model is based on our previous development of a self-consistent shock-in-jet model with relativistic thermal and non-thermal particle distributions evaluated via Monte-Carlo simulations of diffusive shock acceleration, and time-dependent radiative transport. This model has been very successful in modeling spectral variability patterns of several blazars, but has difficulties describing orphan flares, i.e., high-energy flares without a significant counterpart in the low-frequency (synchrotron) radiation component. As a solution, this paper investigates the possibility of a synchrotron mirror component within the shock-in-jet model. It is demonstrated that orphan flares result naturally in this scenario. The model’s applicability to a recently observed orphan gamma-ray flare in the blazar 3C279 is discussed and it is found that only orphan flares with mild (≲ a factor of 2–3) enhancements of the Compton dominance can be reproduced in a synchrotron-mirror scenario, if no additional parameter changes are invoked.

scholarly journals Acceleration of Charged Particles in Astrophysical Plasmas

2021 ◽  
Vol 8 ◽  
Author(s):  
Siming Liu ◽  
J. Randy Jokipii
Keyword(s):  
Particle Acceleration ◽  
Magnetic Fields ◽  
Electric Fields ◽  
Charged Particles ◽  
High Energy ◽  
Shock Acceleration ◽  
High Energy Particle ◽  
Acceleration Of Particles ◽  
Diffusive Shock Acceleration ◽  
Astrophysical Plasmas

The origin of high-energy particles in the Universe is one of the key issues of high-energy solar physics, space science, astrophysics, and particle astrophysics. Charged particles in astrophysical plasmas can be accelerated to very high energies by electric fields. Based on the characteristics of interactions between charged particles and electric fields carried by the background plasma, the mechanisms of charged particle acceleration can be divided into several groups: resonant interactions between plasma waves and particles, acceleration by electric fields parallel to magnetic fields, and acceleration caused by drift of the guiding center of particle gyro-motion around magnetic fields in magnetic field in-homogeneity-related curvature and gradient, etc. According to macroscopic energy conversion mechanisms leading to acceleration of particles, several theories of particle acceleration have been developed: stochastic particle acceleration by turbulent electromagnetic fields, diffusive shock acceleration of particles, and particle acceleration during magnetic re-connections. These theories have their own assumptions and characteristics and find applications in different astrophysical contexts. With advances in high-energy astrophysical observations and in combination with analyses of characteristics of high-energy particle acceleration and radiation, we can better understand the underlying physical processes in dramatically evolving astrophysical environments.

scholarly journals MULTIWAVELENGTH PROBES OF THE ENVIRONS OF RELATIVISTIC SHOCKS IN BLAZAR JETS

2014 ◽  
Vol 28 ◽  
pp. 1460167 ◽  
Author(s):  
MATTHEW G. BARING ◽  
MARKUS BÖTTCHER ◽  
ERROL J. SUMMERLIN
Keyword(s):  
Gamma Ray ◽  
Mean Free Path ◽  
High Energy ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Particle Distributions ◽  
Astrophysical Jet ◽  
Relativistic Shocks ◽  
Diagnostic Potential ◽  
Power Law Index

Diffusive shock acceleration (DSA) at relativistic shocks is likely to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud AGN. An important recent development for blazar science is the ability of Fermi-LAT data to pin down the power-law index of the high energy portion of emission in these sources, and therefore also the index of the underlying non-thermal particle population. This diagnostic potential was not possible prior to Fermi launch, when gamma-ray information was dominated by the highly-absorbed TeV band. This paper highlights how multiwavelength spectra including X-ray band and Fermi data can be used to probe diffusive acceleration in relativistic, oblique, MHD shocks in blazar jets. The spectral index of the non-thermal particle distributions resulting from Monte Carlo simulations of DSA, and the fraction of thermal particles accelerated to non-thermal energies, depend sensitively on the particles' mean free path scale, and also on the magnetic field obliquity to the shock normal. We investigate self-consistently the radiative synchrotron/Compton signatures of the resulting thermal and non-thermal particle distributions. Important constraints on the frequency of particle scattering and the level of field turbulence are identified for the blazar AO 0235+164. The possible interpretation that turbulence levels decline with remoteness from jet shocks, and a significant role for non-gyroresonant diffusion, are discussed.

scholarly journals Constraining the coherence scale of the interstellar magnetic field using TeV gamma-ray observations of supernova remnants

2020 ◽  
Vol 496 (2) ◽  
pp. 2448-2461 ◽  
Author(s):  
Matteo Pais ◽  
Christoph Pfrommer ◽  
Kristian Ehlert ◽  
Maria Werhahn ◽  
Georg Winner
Keyword(s):  
Magnetic Field ◽  
Interstellar Medium ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Galactic Cosmic Rays ◽  
Shock Acceleration ◽  
Interstellar Gas ◽  
Narrow Angle ◽  
Magnetohydrodynamic Simulations ◽  
Tev Gamma Rays

ABSTRACT Galactic cosmic rays (CRs) are believed to be accelerated at supernova remnant (SNR) shocks. In the hadronic scenario, the TeV gamma-ray emission from SNRs originates from decaying pions that are produced in collisions of the interstellar gas and CRs. Using CR-magnetohydrodynamic simulations, we show that magnetic obliquity-dependent shock acceleration is able to reproduce the observed TeV gamma-ray morphology of SNRs such as Vela Jr and SN1006 solely by varying the magnetic morphology. This implies that gamma-ray bright regions result from quasi-parallel shocks (i.e. when the shock propagates at a narrow angle to the upstream magnetic field), which are known to efficiently accelerate CR protons, and that gamma-ray dark regions point to quasi-perpendicular shock configurations. Comparison of the simulated gamma-ray morphology to observations allows us to constrain the magnetic coherence scale λB around Vela Jr and SN1006 to $\lambda _B \simeq 13_{-4.3}^{+13}$ pc and $\lambda _B \gt 200_{-40}^{+50}$ pc, respectively, where the ambient magnetic field of SN1006 is consistent with being largely homogeneous. We find consistent pure hadronic and mixed hadronic-leptonic models that both reproduce the multifrequency spectra from the radio to TeV gamma-rays and match the observed gamma-ray morphology. Finally, to capture the propagation of an SNR shock in a clumpy interstellar medium, we study the interaction of a shock with a dense cloud with numerical simulations and analytics. We construct an analytical gamma-ray model for a core collapse SNR propagating through a structured interstellar medium, and show that the gamma-ray luminosity is only biased by 30 per cent for realistic parameters.

scholarly journals Fermi-LAT and WMAP observations of the supernova remnant Puppis A

2013 ◽  
Vol 9 (S296) ◽  
pp. 295-299
Author(s):  
Marie-Hélène Grondin ◽  
John W. Hewitt ◽  
Marianne Lemoine-Goumard ◽  
Thierry Reposeur ◽  
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
Gamma Ray ◽  
High Energy ◽  
Radio Spectrum ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Large Area ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Γ Ray

AbstractThe supernova remnant (SNR) Puppis A (aka G260.4-3.4) is a middle-aged supernova remnant, which displays increasing X-ray surface brightness from West to East corresponding to an increasing density of the ambient interstellar medium at the Eastern and Northern shell. The dense IR photon field and the high ambient density around the remnant make it an ideal case to study in γ-rays. Gamma-ray studies based on three years of observations with the Large Area Telescope (LAT) aboard Fermi have revealed the high energy gamma-ray emission from SNR Puppis A. The γ-ray emission from the remnant is spatially extended, and nicely matches the radio and X-ray morphologies. Its γ-ray spectrum is well described by a simple power law with an index of ~2.1, and it is among the faintest supernova remnants yet detected at GeV energies. To constrain the relativistic electron population, seven years of Wilkinson Microwave Anisotropy Probe (WMAP) data were also analyzed, and enabled to extend the radio spectrum up to 93 GHz. The results obtained in the radio and γ-ray domains are described in detail, as well as the possible origins of the high energy γ-ray emission (Bremsstrahlung, Inverse Compton scattering by electrons or decay of neutral pions produced by proton interactions).

scholarly journals Energetic Particles in a Flare Loop: Spectra and Radiation Signatures

1990 ◽  
Vol 142 ◽  
pp. 421-427
Author(s):  
P. A. Bespalov ◽  
V. V. Zaitsev ◽  
A. V. Stepanov
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Propagation Model ◽  
Source Spectrum ◽  
High Energy Particle ◽  
Particle Interactions ◽  
Flare Loop ◽  
Energetic Ions ◽  
Particle Spectra ◽  
One Step

It has been shown that high energy particle spectra, particle dynamics, and radiation in a flare loop are determined by wave-particle interactions. The electron-whistler interaction occurs under conditions of strong pitch angle diffusion that makes the particle distribution function isotropic. The flare loop electrons retain information about the particle source spectrum. The interaction of energetic ions with Alfven waves is characterized by strong, moderate, and weak diffusion. The time delays in hard X-ray and gamma-ray emission during one-step acceleration processes might be understood in terms of a trap-plus-turbulent propagation model. The density of precipitating particles is less than or equal to the trapping one. Radiation signatures of flare loop electrons are discussed.

scholarly journals Linking supernovae and supernova remnants. Time-dependent injection in SN1987A and gamma-ray spectrum of IC443

2017 ◽  
Vol 12 (S331) ◽  
pp. 268-273
Author(s):  
O. Petruk ◽  
S. Orlando ◽  
M. Miceli
Keyword(s):  
Gamma Rays ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Supernova Explosion ◽  
Cosmic Ray ◽  
Proton Spectrum ◽  
Stationary Equation ◽  
Particle Injection ◽  
Particle Momentum ◽  
Number Of Particles

AbstractAcceleration times of particles responsible for the gamma-rays in supernova remnants (SNRs) are comparable with SNR age. If the number of particles starting acceleration was varying during early times after the supernova explosion then this variation should be reflected in the shape of the gamma-ray spectrum. In order to analyse this effect, we consider the time variation of the radio spectral index in SN1987A and solution of the non-stationary equation for particle acceleration. We reconstruct evolution of the particle injection in SN1987A, apply it to derive the particle momentum distribution in IC443 and model its gamma-ray spectrum. We show that: i) observed break in the proton spectrum around 50 GeV in IC443 is a consequence of the variation of the cosmic ray injection; ii) shape of the hadronic gamma-ray spectrum in SNRs critically depends on the temporal variation of the cosmic ray injection in the immediate post explosion phases.

scholarly journals Particle Acceleration in High-Energy Gamma-Ray Sources

1994 ◽  
Vol 142 ◽  
pp. 877-881
Author(s):  
David Eichler
Keyword(s):  
Gamma Rays ◽  
Production Efficiency ◽  
Gamma Ray ◽  
High Energy ◽  
Thick Target ◽  
Shock Acceleration ◽  
High Production Efficiency ◽  
Energy Gamma ◽  
High Production ◽  
High Energy Particles

AbstractMany proficient gamma-ray sources show energy spectra that are consistent with E−2 primary spectra. Such sources include recently identified gamma-ray quasars and some gamma-ray bursts. Assuming thick target conversion, this is consistent with shock acceleration, and the dominance of the gamma rays of the luminosity is also consistent with previous predictions of high production efficiency of fresh cosmic rays in shocks. The spectral cutoffs in the gamma rays may offer clues as to whether the high-energy particles are electrons or protons. Resolution of this matter might have implications for the nature of the sources and for theory of shock accelerated electrons.Subject headings: acceleration of particles — gamma rays: bursts — shock waves

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