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Collisionless shock acceleration of protons and C$^{6+}$ ions has been achieved by the interaction of a 10$^{20}$ W/cm$^2$, 1 $\mu$m laser with a near-critical density plasma. Ablation of the initially solid density target by a secondary…

The analysis of Balmer-dominated optical spectra from non-radiative (adiabatic) SNRs has shown that the ratio of the electron to proton temperature temperature at the blast wave is close to unity at v_s <= 400 km/s, but declines sharply…

Astrophysics · Physics 2009-11-11 Parviz Ghavamian , J. Martin Laming , Cara E. Rakowski

Diffusive shock acceleration in the environs of a remnant's expanding shell is a popular candidate for the origin of SNR gamma-rays. In this paper, results from our study of non-linear effects in shock acceleration theory and their impact…

The theory of diffusive particle acceleration explains the spectral properties of the cosmic rays below energies of approx. 10^6 GeV as produced at strong shocks in supernova remnants (SNR's). To supply the observed flux of cosmic rays, a…

Astrophysics · Physics 2007-05-23 U. D. J. Gieseler , T. W. Jones , Hyesung Kang

Supernova remnants (SNRs) are believed to produce the majority of galactic cosmic rays (CRs). SNRs harbor non-relativistic collisionless shocks responsible for acceleration of CRs via diffusive shock acceleration (DSA), in which particles…

High Energy Astrophysical Phenomena · Physics 2022-12-20 Artem Bohdan

Particle acceleration at astrophysical shocks may be very efficient if magnetic scattering is self-generated by the same particles. This nonlinear process adds to the nonlinear modification of the shock due to the dynamical reaction of the…

Astrophysics · Physics 2009-11-11 Elena Amato , Pasquale Blasi

We investigate the interaction of nonthermal ions (protons and nuclei) accelerated in an ultrarelativistic blastwave with the pre-existing magnetic field of the medium into which the blastwave propagates. While particle acceleration…

Astrophysics · Physics 2009-11-13 Sean M. Couch , Milos Milosavljevic , Ehud Nakar

We investigate the theoretical and observational implications of the acceleration of protons and heavier nuclei in supernova remnants (SNRs). By adopting a semi-analytical technique, we study the non-linear interplay among particle…

High Energy Astrophysical Phenomena · Physics 2017-08-23 D. Caprioli , P. Blasi , E. Amato

The theory of shock acceleration predicts the maximum particle energy to be limited only by the acceleration time and the size (geometry) of the shock. This led to optimistic estimates for the galactic cosmic ray energy achievable in the…

Astrophysics · Physics 2008-11-26 M. A. Malkov , P. H. Diamond , T. W. Jones

Precise measurements of galactic cosmic rays revealed a significant difference between the rigidity spectral indices of protons and helium ions. This finding is a notable contrast to the commonly accepted theoretical prediction that…

High Energy Astrophysical Phenomena · Physics 2019-02-27 A. Hanusch , T. Liseykina , M. Malkov

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…

High Energy Astrophysical Phenomena · Physics 2019-03-11 A. M. Bykov , F. Vazza , J. A. Kropotina , K. P. Levenfish , F. B. S. Paerels

First order Fermi acceleration at astrophysical shocks is often invoked as a mechanism for the generation of non-thermal particles. This mechanism is especially simple in the approximation that the accelerated particles behave like test…

Astrophysics · Physics 2015-06-24 Pasquale Blasi

Shocks of supernova remnants (SNRs) accelerate charged particles up to 100 TeV range via diffusive shock acceleration (DSA) mechanism. It is believed that shocks of SNRs are the main contributors to the pool of Galactic cosmic rays,…

High Energy Astrophysical Phenomena · Physics 2023-04-05 Jacco Vink , Aya Bamba

Diffusive shock acceleration (DSA) of particles at collisionless shocks is the major accepted paradigm about the origin of cosmic rays (CRs). As a theory it was developed during the late 1970s in the so-called test-particle case. If one…

High Energy Astrophysical Phenomena · Physics 2023-10-03 Bojan Arbutina

The Balmer line profiles of nonradiative supernova remnant shocks provide the means to measure the post-shock proton velocity distribution. While most analyses assume a Maxwellian velocity distribution, this is unlikely to be correct. In…

Astrophysics · Physics 2009-11-13 J. C. Raymond , Philip A. Isenberg , J. M. Laming

In addition to electrons and protons, nonrelativistic quasiparallel shocks are expected to possess the ability to accelerate heavy ions. The shocks in supernova remnants are generally supposed to be accelerators of the Galactic cosmic rays,…

High Energy Astrophysical Phenomena · Physics 2022-04-20 Jun Fang , Qi Xia , Shiting Tian , Liancheng Zhou , Huan Yu

Although the origin of cosmic rays (CRs) remains an open question, collisionless magnetized shock waves are widely regarded as key sites for particle acceleration. Recent theories further suggest that shock-shock collisions in stellar…

A rapidly growing amount of evidences, mostly coming from the recent gamma-ray observations of Galactic supernova remnants (SNRs), is seriously challenging our understanding of how particles are accelerated at fast shocks. The cosmic-ray…

High Energy Astrophysical Phenomena · Physics 2015-06-05 Damiano Caprioli

Electron acceleration to non-thermal, ultra-relativistic energies (~ 10-100 TeV) is revealed by radio and X-ray observations of shocks in young supernova remnants (SNRs). The diffusive shock acceleration (DSA) mechanism is usually invoked…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Mario A. Riquelme , Anatoly Spitkovsky

We recently proposed a new technique of plasma tailoring by laser-driven hydrodynamic shockwaves generated on both sides of a gas jet [J.-R. Marqu\`es et al., Phys. Plasmas 28, 023103 (2021)]. In the continuation of this numerical work, we…