Related papers: Cosmic Ray Acceleration by E-Parallel Reconnection…
We propose that a hierarchical shock model$\unicode{x2014}$including supernova remnant shocks, galactic wind termination shocks, and accretion shocks around cosmic filaments and galaxy clusters$\unicode{x2014}$can naturally explain the…
Ultra-high energy cosmic rays (UHECRs) may be produced in active galactic nuclei (AGN) or gamma-ray burst (GRB) jets. I argue that magnetic reconnection in jets can accelerate UHECRs rather independently of physical processes in the…
The energy losses and spectra of Ultra High Energy Cosmic Rays (UHECR) are calculated for protons as primary particles. The attention is given to the energy losses due to electron-positron production in collisions with the microwave 2.73 K…
It has been proposed that Ultra-High-Energy Cosmic Rays (UHECRs) up to $10^{20}$eV could be produced in the relativistic jets of powerful Active Galactic Nuclei (AGNs) via a one-shot reacceleration of lower-energy CRs produced in supernova…
Ultra high energy cosmic rays (UHECRs) are expected to be accelerated in astrophysical sources and to travel through extragalactic space before hitting the Earth atmosphere. They interact both with the environment in the source and with the…
The origin, propagation, and mechanisms of acceleration of the ultra-high energy cosmic rays (UHECRs) are not yet well understood. Aiming for a better interpretation of the available experimental data, these data have to be confronted with…
In spite a lot of theoretical and experimental effort that has been achieved in ultra-high energy cosmic ray (UHECR) scattering research in last few decades, some questions remain unanswered, or partially answered. Two of them, that will be…
Combined recent data from cosmic-ray detectors and gamma-ray detectors have produced some surprising insights regarding the sources of ultrahigh-energy cosmic rays (UHECRs), magnetic fields inside and outside the Milky Way, and the…
We report the results of 3-D simulations of non-diffusive propagation of Ultra-High Energy Cosmic Rays (UHECR) (E > 10^{20} eV) through the intergalactic and extended halo media. We quantify the expected angular and temporal correlations…
Ultra-high energy cosmic rays (UHECRs) accelerated in the jets of active galactic nuclei can accumulate in high magnetic field, ~100 kpc-scale regions surrounding powerful radio galaxies. Photohadronic processes involving UHECRs and photons…
Since their first observation in 1962, the existence of Ultra High Energy Cosmic Rays (UHECR) remains a mystery in modern astrophysics. Those cosmic rays, with energies well above 50 EeV ($50\times 10^{18}$eV), can hardly be accelerated,…
A model is introduced, in which the irregularity spectrum of the Galactic magnetic field beyond the dissipation length scale is first a Kolmogorov spectrum $k^{-5/3}$ at small scales $\lambda \, = \, 2 \pi/k$ with $k$ the wave-number, then…
In this paper, we have made an accurate investigation of proton acceleration in GRBs and we have predicted a possible signature of cosmic rays, in a sufficiently baryon-loaded fireball, via GeV $\gamma$-ray emission produced by…
The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. A key…
Ultrahigh-energy cosmic rays (UHECRs) are the highest energy messenger from space, with energies exceeding 1 EeV. Although UHECRs were discovered over 60 years ago, their origin still remains a mystery. Pinpointing sources of UHECRs is…
Galactic cosmic rays (CRs) are accelerated by astrophysical shocks, primarily supernova remnants (SNRs), via diffusive shock acceleration (DSA), an efficient mechanism that predicts power-law energy distributions of CRs. However,…
Cosmic rays are charged relativistic particles that reach the Earth with extremely high energies, providing striking evidence of the existence of effective accelerators in the Universe. Below an energy around $\sim 10^{17}$ eV cosmic rays…
Ultra high energy cosmic rays (UHECRs) probably originate in extreme conditions in which extra dimension effects might be important. In this paper we calculate the correction in black hole accretion mechanisms due to extra dimension effects…
If ultra-high energy cosmic rays (UHECRs) are accelerated at astrophysical point sources, the identification of such sources can be achieved if there is some kind of radiation at observable wavelengths that may be associated with the…
We investigate a mechanism for accelerating cool (10$^4$ K) clouds in the circumgalactic medium (CGM) with cosmic rays (CRs), possibly explaining some characteristics of observed high velocity clouds (HVCs). Enforcing CRs to stream down…