Related papers: Cosmic Rays: The Second Knee and Beyond
We outline two concepts to explain Ultra High Energy Cosmic Rays (UHECRs), one based on radio galaxies and their relativistic jets and terminal hot spots, and one based on relativistic Super-Novae (SNe) or Gamma Ray Bursts (GRBs) in…
The origin mechanism of the cosmic-ray knee region remains an unresolved mystery, with acceleration, interaction, and propagation models drawing significant attention. The latest experimental observations of the PeV total spectrum,…
We will review the main physical aspects of Ultra High Energy Cosmic Rays. We will discuss in particular their propagation through astrophysical backgrounds, focusing on the latest experimental observations of HiRes, Telescope Array and…
A detailed investigation of radio galaxies has recently stressed these sources as the possible origin of the cosmic rays observed above $3\,\text{EeV}$. Here, the relevance of this model at energies below $3\,\text{EeV}$ is investigated.…
The sources of ultra-high energy cosmic rays (UHECRs) are still one of the main open questions in high-energy astrophysics. If UHECRs are accelerated in astrophysical sources, they are expected to produce high-energy photons and neutrinos…
This paper presents the highlights from the recent measurements of the energy spectrum, mass composition, and arrival directions of the ultra-high energy ($> 10^{17}$ eV = 0.1 EeV) cosmic rays (UHECR) by the Pierre Auger Observatory. The…
In the cosmic ray spectrum, there are two knees (abrupt changes of slopes) located around the energies $E_{th}=10^{15.5}$ eV and $10^{17.8}$ eV respectively. Based on the pioneering work by Kostelecky and Ehrlich, we ascribe the first knee…
The Ultra-high energy cosmic ray energy spectrum summarized by the AGASA collaboration indicates clearly that the cosmic ray spectrum extends well beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off at \sim 5 x 10^19 eV. Furthermore, despite…
Although the existence of cosmic rays with energies extending well above $10^{19}$ eV has been confirmed, their origin remains one of the most important questions in astro-particle physics today. Several source models have been proposed for…
Ultra High Cosmic Rays (UHECR) Astronomy may be correlated to a primary parental Neutrino Astronomy: indeed any far BL Lac Jet or GRB, sources of UHECR, located at cosmic edges, may send its signal, overcoming the severe GZK cut-off, by…
Ultra-high energy cosmic rays (UHECRs) are the highest energy messengers of the present universe, with energies up to $10^{20}$ eV. Studies of astrophysical particles (nuclei, electrons, neutrinos and photons) at their highest observed…
Recent results obtained with the Pierre Auger Observatory are described. These include measurements of the spectrum, anisotropies and composition of ultra-high energy cosmic rays. The ankle of the spectrum is measured at $4\times…
A posteriori anisotropy study of ultra-high energy cosmic rays (UHECRs) with the Pierre Auger Observatory (PAO) has shown evidence of excess of cosmic ray particles above 55 EeV within $18^{\circ}$ of the direction of the radio galaxy…
Radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 EeV, called ultra-high-energy cosmic rays (UHECRs). Here, the key issues from a recent investigation are summed up, where the individual…
Our Universe is described jointly by Einstein's relativity principle and the quantum principle; there the existence of the smallest units of matter, such as electrons, neutrinos, quarks, and photons, is well established and the smallest…
The energy at which cosmic rays from extra-galactic sources begin to dominate over those from galactic sources is an important open question in astroparticle physics. A natural candidate is the energy at the 'ankle' in the approximately…
Abstract. We discuss recent results on the clustering, composition and distribution of Ultra-High Energy Cosmic Rays (UHECR) in the sky; from the energy of several tens of EeV in the dipole anisotropy, up to the highest energy of a few…
Motivated by recent Pierre Auger result on the correlation of the highest-energy cosmic rays with the nearby active galactic nuclei, we explore possible ultrahigh energy cosmic ray (UHECR) source distributions and their effects on GZK…
We demonstrate that the energy spectra of Ultra High Energy Cosmic Rays (UHECR) as observed by AGASA, Fly's Eye, HiRes and Yakutsk detectors, have the imprints of UHE proton interaction with the CMB radiation as the dip centered at $E\sim…
Some general features of cosmic ray acceleration are summarized along with some inferences that can be drawn concerning the origin of the UHE component. The UHE luminosity density is found to be similar to that derived for GeV cosmic rays…