Ion Acceleration in Non-Relativistic Astrophysical Shocks

Gargaté, L.; Spitkovsky, Anatoly

doi:10.1088/0004-637x/744/1/67

Cited by 103 publications

(100 citation statements)

References 55 publications

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“…This ratio is practically independent of θ Bn for quasi-parallel configurations, whereas ion injection at quasi-perpendicular shocks is negligible. These results are also in agreement with earlier parameter studies by Giacalone et al (1997) and Gargaté & Spitkovsky (2012). A minimal model of the ion-shock interaction was recently proposed by Caprioli et al (2015).…”

Section: Introductionsupporting

confidence: 92%

Ion Acceleration at the Quasi-Parallel Bow Shock: Decoding the Signature of Injection

Sundberg

Haynes

Burgess

et al. 2016

ApJ

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Collisionless shocks are efficient particle accelerators. At Earth, ions with energies exceeding 100 keV are seen upstream of the bow shock when the magnetic geometry is quasi-parallel, and large-scale supernova remnant shocks can accelerate ions into cosmic-rayenergies. This energization is attributed to diffusive shock acceleration;however, for this process to become active, the ions must first be sufficiently energized. How and where this initial acceleration takes place has been one of the key unresolved issues in shock acceleration theory. Using Cluster spacecraft observations, we study the signatures of ion reflection events in the turbulent transition layer upstream of the terrestrial bow shock, and with the support of a hybrid simulation of the shock, we show that these reflection signatures are characteristic of the first step in the ion injection process. These reflection events develop in particular in the region where the trailing edge of large-amplitude upstream waves intercept the local shock ramp and the upstream magnetic field changes from quasi-perpendicular to quasi-parallel. The dispersed ion velocity signature observed can be attributed to a rapid succession of ion reflections at this wave boundary. After the ions' initial interaction with the shock, they flow upstream along the quasi-parallel magnetic field. Each subsequent wavefront in the upstream region will sweep the ions back toward the shock, where they gain energy with each transition between the upstream and the shock wave frames. Within three to five gyroperiods, some ions have gained enough parallel velocity to escape upstream, thus completing the injection process.

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Section: Introductionsupporting

confidence: 92%

Ion Acceleration at the Quasi-Parallel Bow Shock: Decoding the Signature of Injection

Sundberg

Haynes

Burgess

et al. 2016

ApJ

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“…Existing collisionless shock simulations, hybrid and PIC simulations, have focused on strong shocks or low beta-plasma. [106][107][108] The orientation of the magnetic field with respect to the shock normal is also important, since it strongly influences the physics of the shock structure. 106,109 A connected, unresolved ingredient in nonlinear CR shock theory is the level of amplification of the magnetic field and its distribution within the shock due to CR-driven instabilities.…”

Section: Shock Acceleration In the Icm And Open Questionsmentioning

confidence: 99%

Cosmic Rays in Galaxy Clusters and Their Nonthermal Emission

Brunetti¹,

Jones

2014

Int. J. Mod. Phys. D

627

732

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Radio observations prove the existence of relativistic particles and magnetic field associated with the intra-cluster-medium (ICM) through the presence of extended synchrotron emission in the form of radio halos and peripheral relics. This observational evidence has fundamental implications on the physics of the ICM. Non-thermal components in galaxy clusters are indeed unique probes of very energetic processes operating within clusters that drain gravitational and electromagnetic energy into cosmic rays and magnetic fields. These components strongly affect the (micro-)physical properties of the ICM, including viscosity and electrical conductivities, and have also potential consequences on the evolution of clusters themselves. The nature and properties of cosmic rays in galaxy clusters, including the origin of the observed radio emission on cluster-scales, have triggered an active theoretical debate in the last decade. Only recently we can start addressing some of the most important questions in this field, thanks to recent observational advances, both in the radio and at high energies. The properties of cosmic rays and of cluster non-thermal emissions depend on the dynamical state of the ICM, the efficiency of particle acceleration mechanisms in the ICM and on the dynamics of these cosmic rays. In this review we discuss in some detail the acceleration and transport of cosmic rays in galaxy clusters and the most relevant observational milestones that have provided important steps on our understanding of this physics. Finally, looking forward to the possibilities from new generations of observational tools, we focus on what appear to be the most important prospects for the near future from radio and high-energy observations.

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“…The width of the shock transition region was found to be about 100 ion inertial lengths, independent of the shock velocity. The hybrid plasma simulations with kinetic treatment of ions and fluid electron description (see, e.g., Winske and Quest 1988, Winske et al 1990, Giacalone et al 1997, Treumann 2009, Gargaté and Spitkovsky 2012, Burgess and Scholer 2013 allow to study domains of some thousands gyroradii of upstream protons around non-relativistic shocks. Two-dimensional hybrid simulations of a quasi-parallel shock with the Alfven Mach number M a =6 by Gargaté and Spitkovsky (2012) revealed a power law distribution of energetic ions of index about 2±0.2 in the shock downstream.…”

Section: Particle Acceleration By Collisionless Shocksmentioning

confidence: 99%

Nonthermal particles and photons in starburst regions and superbubbles

Bykov

2014

Astron Astrophys Rev

118

102

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Starforming factories in galaxies produce compact clusters and loose associations of young massive stars. Fast radiation-driven winds and supernovae input their huge kinetic power into the interstellar medium in the form of highly supersonic and superalfvenic outflows. Apart from gas heating, collisionless relaxation of fast plasma outflows results in fluctuating magnetic fields and energetic particles. The energetic particles comprise a long-lived component which may contain a sizeable fraction of the kinetic energy released by the winds and supernova ejecta and thus modify the magnetohydrodynamic flows in the systems. We present a concise review of observational data and models of nonthermal emission from starburst galaxies, superbubbles, and compact clusters of massive stars. Efficient mechanisms of particle acceleration and amplification of fluctuating magnetic fields with a wide dynamical range in starburst regions are discussed. Sources of cosmic rays, neutrinos and multi-wavelength nonthermal emission associated with starburst regions including potential galactic "PeVatrons" are reviewed in the global galactic ecology context.

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Ion Acceleration in Non-Relativistic Astrophysical Shocks

Cited by 103 publications

References 55 publications

Ion Acceleration at the Quasi-Parallel Bow Shock: Decoding the Signature of Injection

Ion Acceleration at the Quasi-Parallel Bow Shock: Decoding the Signature of Injection

Cosmic Rays in Galaxy Clusters and Their Nonthermal Emission

Nonthermal particles and photons in starburst regions and superbubbles

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