scholarly journals Multi-scale simulations of particle acceleration in astrophysical systems

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Alexandre Marcowith ◽  
Gilles Ferrand ◽  
Mickael Grech ◽  
Zakaria Meliani ◽  
Illya Plotnikov ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Energetic Particle ◽  
Large Scale ◽  
Numerical Study ◽  
Cosmic Ray ◽  
Compact Objects ◽  
Shock Acceleration ◽  
Fermi Acceleration ◽  
The Subject ◽  
Astrophysical Flows

AbstractThis review aims at providing an up-to-date status and a general introduction to the subject of the numerical study of energetic particle acceleration and transport in turbulent astrophysical flows. The subject is also complemented by a short overview of recent progresses obtained in the domain of laser plasma experiments. We review the main physical processes at the heart of the production of a non-thermal distribution in both Newtonian and relativistic astrophysical flows, namely the first and second order Fermi acceleration processes. We also discuss shock drift and surfing acceleration, two processes important in the context of particle injection in shock acceleration. We analyze with some details the particle-in-cell (PIC) approach used to describe particle kinetics. We review the main results obtained with PIC simulations in the recent years concerning particle acceleration at shocks and in reconnection events. The review discusses the solution of Fokker–Planck problems with application to the study of particle acceleration at shocks but also in hot coronal plasmas surrounding compact objects. We continue by considering large scale physics. We describe recent developments in magnetohydrodynamic (MHD) simulations. We give a special emphasis on the way energetic particle dynamics can be coupled to MHD solutions either using a multi-fluid calculation or directly coupling kinetic and fluid calculations. This aspect is mandatory to investigate the acceleration of particles in the deep relativistic regimes to explain the highest cosmic ray energies.

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 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 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.

FIRST-ORDER DISTRIBUTED FERMI ACCELERATION OF COSMIC RAY HADRONS IN NON-UNIFORM MAGNETIC FIELDS

2009 ◽  
Vol 24 (19) ◽  
pp. 1461-1472 ◽  
Author(s):  
R. SCHLICKEISER
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Large Scale ◽  
Cosmic Ray ◽  
Acceleration Process ◽  
Fermi Acceleration ◽  
Helicity State ◽  
First Order ◽  
Physical Mechanisms ◽  
Guide Magnetic Field

Large-scale spatial variations of the guide magnetic field of interplanetary and interstellar plasmas give rise to the adiabatic focusing term in the Fokker–Planck transport equation of cosmic rays. As a consequence of the adiabatic focusing term, the diffusion approximation to cosmic ray transport in the weak focusing limit gives rise to first-order Fermi acceleration of energetic particles if the product HL of the cross helicity state of Alfvenic turbulence H and the focusing length L is negative. The basic physical mechanisms for this new acceleration process are clarified and the astrophysical conditions for efficient acceleration are investigated. It is shown that in the interstellar medium this mechanism preferentially accelerates cosmic ray hadrons over 10 orders of magnitude in momentum. Due to heavy Coulomb and ionization losses at low momenta, injection or preacceleration of particles above the threshold momentum pc≃0.17Z2/3 GeV /c is required.

scholarly journals Particle acceleration in fast magnetic reconnection

2010 ◽  
Vol 6 (S274) ◽  
pp. 62-71
Author(s):  
A. Lazarian ◽  
G. Kowal ◽  
E. de Gouveia Dal Pino ◽  
E. Vishniac
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Numerical Simulations ◽  
Large Scale ◽  
Particle Accelerator ◽  
Fermi Acceleration ◽  
Origin And Evolution ◽  
First Order ◽  
Large Scale Magnetic Field ◽  
Fast Reconnection

AbstractOur numerical simulations show that the reconnection of magnetic field becomes fast in the presence of weak turbulence in the way consistent with the Lazarian & Vishniac (1999) model of fast reconnection. This process in not only important for understanding of the origin and evolution of the large-scale magnetic field, but is seen as a possibly efficient particle accelerator producing cosmic rays through the first order Fermi process. In this work we study the properties of particle acceleration in the reconnection zones in our numerical simulations and show that the particles can be efficiently accelerated via the first order Fermi acceleration.

scholarly journals Active Galactic Nuclei: Jets as the Source of Hadrons and Neutrinos

2014 ◽  
Vol 1 (1) ◽  
pp. 269-273
Author(s):  
Athina Meli ◽  
Paolo Ciarcelluti
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Cosmic Ray ◽  
High Energy ◽  
Plasma Jets ◽  
Shock Acceleration ◽  
Fermi Acceleration ◽  
Acceleration Mechanism ◽  
Relativistic Shocks

Active galactic nuclei are extragalactic sources, and their relativistic hot-plasma jets are believed to be the main candidates of the cosmic-ray origin, above the so-called knee region of the cosmic-ray spectrum. Relativistic shocks, either single or multiple, have been observed or been theorized to be forming within relativistic jet channels in almost all active galactic nuclei sources. The acceleration of non-thermal particles (e.g. electrons, protons) via the shock Fermi acceleration mechanism, is believed to be mainly responsible for the power-law energy distribution of the observed cosmic-rays, which in very high energies can consequently radiate high energy gamma-rays and neutrinos, through related radiation channels. Here, we will focus on the primary particle (hadronic) shock acceleration mechanism, and we will present a comparative simulation study of the properties of single and multiple relativistic shocks, which occur in AGN jets. We will show that the role of relativistic (quasi-parallel either quasi-perpendicular) shocks, is quite important since it can dramatically alter the primary CR spectral indices and acceleration eciencies. These properties being carried onto gamma-ray and neutrino radiation characteristics, makes the combination of them a quite appealing theme for relativistic plasma and shock acceleration physics, as well as observational cosmic-ray, gamma-ray and neutrino astronomy.

scholarly journals Limiting the shock acceleration of cosmic ray protons in the ICM

2020 ◽  
Vol 495 (1) ◽  
pp. L112-L117 ◽  
Author(s):  
D Wittor ◽  
F Vazza ◽  
D Ryu ◽  
H Kang
Keyword(s):  
Cosmic Rays ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Cosmic Ray ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Magnetic Field Topology ◽  
Tracer Particles ◽  
Γ Rays ◽  
Massive Galaxy

ABSTRACT Observations of large-scale radio emissions prove the existence of shock accelerated cosmic ray electrons in galaxy clusters, while the lack of detected γ-rays limits the acceleration of cosmic ray protons in galaxy clusters. This challenges our understanding of how diffusive shock acceleration works. In this work, we couple the most updated recipes for shock acceleration in the intracluster medium to state-of-the-art magnetohydrodynamical simulations of massive galaxy clusters. Furthermore, we use passive tracer particles to follow the evolution of accelerated cosmic rays. We show that when the interplay between magnetic field topology and the feedback from accelerated cosmic rays is taken into account, the latest developments of particle acceleration theory give results that are compatible with observational constraints.

scholarly journals Particle Acceleration Mechanisms

1994 ◽  
Vol 142 ◽  
pp. 515-520
Author(s):  
R. D. Blandford
Keyword(s):  
Particle Acceleration ◽  
Large Scale ◽  
Magnetic Energy ◽  
Cosmic Ray ◽  
High Energy ◽  
High Energy Particle ◽  
Common Channel ◽  
Energy Particle ◽  
Particle Injection ◽  
Physical Mechanisms

AbstractHigh-energy particle acceleration is observed to proceed in a diverse variety of astrophysical sites ranging from the terrestrial aurorae to the most distant quasars. Particle acceleration is a fairly common channel for the release of large-scale kinetic, rotational, and magnetic energy. Physical mechanisms include electrostatic acceleration, stochastic processes and diffusive shock energization. Cosmic-ray energy spectra have shapes which reflect escape, collisional, and radiative losses. The overall acceleration efficiency is controlled by the low-energy particle injection which may, in turn, feed back into the energization. Recent observational developments, which illustrate these general principles and raise fresh questions, are briefly summarized.Subject heading: acceleration of particles

Development of a Physics-Based Prototype Model Chain for Solar Energetic Particle Acceleration and Transport Forecasting for the Inner Heliosphere

2020 ◽  
Author(s):  
Kamen Kozarev ◽  
Rositsa Miteva ◽  
Momchil Dechev ◽  
Pietro Zucca
Keyword(s):  
Particle Acceleration ◽  
Energetic Particle ◽  
Large Scale ◽  
Numerical Models ◽  
Time Dependent ◽  
Data Driven ◽  
Radiation Environment ◽  
Prototype Model ◽  
Energetic Particle Acceleration ◽  
Inner Heliosphere

<p>We present the project <strong>SPREAdFAST</strong> – Solar Particle Radiation Environment Analysis and Forecasting - Acceleration and Scattering Transport. This investigation fulfills a vital component of the space weather requirements of ESA’s Space Situational Awareness program by contributing to the capability to protect space assets from solar activity space radiation. It will allow for producing predictions of SEP fluxes at multiple locations in the inner heliosphere, by modelling their acceleration at Coronal Mass Ejections (CMEs) near the Sun, and their subsequent interplanetary transport using a physics-based, data-driven approach. The system prototype will incorporate results from our scientific investigations, the modification and linking of existing open source scientific software, and its adaptation to the goals of the proposed work. It will incorporate a chain of data-driven analytic and numerical models, for estimating: coronal magnetic fields; dynamics of large-scale coronal (CME-driven) shock waves; energetic particle acceleration; scatter-based (not simple ballistic), time-dependent SEP propagation in the heliosphere to specific time-dependent locations.</p>

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