Related papers: Particle Acceleration in Astrophysical Sources
Considerations of the collision losses for protons traversing the 2.7 K black body microwave radiation field have led to the conclusion that the highest energy cosmic rays, those observed at $\geq 10^{20}$ eV, must come from sources within…
The sources of ultrahigh-energy cosmic rays (UHECRs) have been stubbornly elusive. However, the latest report of the Pierre Auger Observatory provides a compelling indication for a possible correlation between the arrival directions of…
The presence of relativistic particles at the center of our galaxy is evidenced by the diffuse TeV emission detected from the inner $\sim$$2^\circ$ of the Galaxy. Although it is not yet entirely clear whether the origin of the TeV photons…
Although Galactic cosmic rays (protons and nuclei) are widely believed to be dominantly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery [1].…
Nature produces cosmic ray particles, probably protons, with energies well above $10^{20}$ eV -- how are they produced? Where do they come from? Gamma rays with energies above $10^{13}$ eV are produced in jets of active galaxies -- are…
Gamma-ray bursts and ultra-high-energy cosmic rays provide an important testing ground for fundamental physics. A simple-minded analysis of some gamma-ray bursts would lead to a huge estimate of the overall energy emitted, and this…
The 320 EeV air shower detected by the Fly's Eye poses an important problem. Careful analysis of pathlength limitations for the possible particle types due to cosmic background radiation verifies that the particle very likely traveled less…
The search for a theory of the origin of cosmic rays that may be considered as a standard, agreeable model is still ongoing. On one hand, much circumstantial evidence exists of the fact that supernovae in our Galaxy play a crucial role in…
We find the general requirements, set by classical electrodynamics, to the sources of extremely high-energy cosmic rays (EHECRs). It is shown that the parameters of EHECR accelerators are strongly limited not only by the particle…
Cosmic rays are the most outstanding example of accelerated particles. They are about 1\% of the total mass of the Universe, so that cosmic rays would represent by far the most important energy transformation process of the Universe.…
Galactic cosmic rays are widely believed to be accelerated in expanding shock waves initiated by supernova explosions. The theory of diffusive shock acceleration of cosmic rays is now well established, but two fundamental questions remain…
Superbubbles (SBs) are amongst the greatest injectors of energy into the Galaxy, and have been proposed to be the acceleration site of Galactic cosmic rays. They are thought to be powered by the fast stellar winds and powerful supernova…
We explore inferences on ultrahigh energy cosmic ray (UHECR) source environments -- constrained by the spectrum and composition of UHECRs and non-observation of extremely high energy neutrinos -- and their implications for the observed high…
Gamma-ray bursts (GRBs) are sources of energetic, highly variable fluxes of gamma rays, which demonstrates that they are powerful particle accelerators. Besides relativistic electrons, GRBs should also accelerate high-energy hadrons, some…
Astronomy at the highest energies observed must be performed by studying neutrinos rather than photons because the universe is opaque to photons of these energies. By making observations of neutrinos with energies above 10 EeV one can…
Evidences of non-thermal X-ray emission and TeV gamma-rays from the supernova remnants (SNRs) has strengthened the hypothesis that primary Galactic cosmic-ray electrons are accelerated in SNRs. High energy electrons lose energy via…
Particle acceleration occurs on a range of scales from AU in the heliosphere to Mpc in clusters of galaxies and to energies ranging from MeV to EeV. A number of acceleration processes have been proposed, but diffusive shock acceleration…
In this article we examine the hypothesis that the highest energy cosmic rays are complex nuclei from extragalactic sources. Under reasonable physical assumptions, we show that the nearby metally rich starburst galaxies (M82 and NGC 253)…
The Sun stands out as the closest and clearest astrophysical accelerator of cosmic rays, while other objects within and beyond the galaxy remain enigmatic. It is probable that the cosmic ray spectrum and mass components from these celestial…
Supernova remnants (SNRs) are thought to be the most plausible sources of Galactic cosmic rays. One of the principal questions is whether they are accelerating particles up to the maximum energy of Galactic cosmic rays ($\sim$PeV). In this…