Related papers: The Galactic cosmic-ray Sun shadow observed by HAW…
We review some of the recent progress in our knowledge about high-energy cosmic rays, with an emphasis on the interpretation of the different observational results. We discuss the effects that are relevant to shape the cosmic ray spectrum…
Cosmic rays are hampered by the Moon and a deficit in its direction is expected (the so-called \emph{Moon shadow}). The Moon shadow is an important tool to determine the performance of an air shower array. In fact, the displacement of the…
The slope of the locally measured spectrum of cosmic rays varies from 2.8 for protons with energies below 200 GeV down to 2.5 for heavy nuclei with energies in the TeV-PeV range. It is not clear if the locally measured slope values are…
The particle lateral distribution function (LDF) of air showers at a given altitude is sensitive to the mass composition and primary energy of cosmic rays. Studies of the LDF are difficult to perform due to experimental effects such as…
Due to fundamental limitations of accelerators, only cosmic rays can give access to centre-of- mass energies more than one order of magnitude above those reached at the LHC. In fact, extreme energy cosmic rays (1018 eV - 1020 eV) are the…
The Sun emits copious amounts of photons and neutrinos in an approximately spatially isotropic distribution. Diffuse $\gamma$-rays and ultra-high energy (UHE) neutrinos from extragalactic sources may subsequently interact and annihilate…
The TeV gamma ray sky is observable by recording footprints of extensive air showers with an array of particle detectors. In the northern hemisphere there are currently two projects employing this technique: The HAWC gamma ray observatory…
The High-Altitude Water Cherenkov (HAWC) observatory in central Mexico is currently the world's only synoptic survey instrument for gamma rays above 1 TeV. Because there is significant interest in covering the full TeV sky with a survey…
The absorption of cosmic rays by the sun produces a shadow at the earth. The angular offset and broadening of the shadow are determined by the magnitude and structure of the interplanetary magnetic field (IPMF) in the inner solar system. We…
Supernova remnants (SNRs) have long been hypothesized as the main source of Galactic Cosmic Rays up to PeV energies. Some of them have indeed been shown to accelerate protons to TeV energies and above. But which of them are indeed efficient…
Waves and oscillations have been observed in the Sun's atmosphere for over half a century. While such phenomena have readily been observed across the entire electromagnetic spectrum, spanning radio to gamma-ray sources, the underlying role…
The accurate determination of the elemental composition of cosmic rays at high energies is expected to provide crucial clues on the origin of these particles. Previous direct measurements of composition have been limited by experiment…
Deciphering and understanding the small-scale magnetic activity of the quiet solar photosphere should help to solve many of the key problems of solar and stellar physics, such as the magnetic coupling to the outer atmosphere and the coronal…
The High-Altitude Water Cherenkov (HAWC) Observatory comprises 300 water Cherenkov detectors, each equipped with four photomultipliers, located on the Volc\'{a}n Sierra Negra in Mexico at 4,100 masl. This observatory can detect gamma rays…
The Sun is a bright gamma-ray source due to hadronic cosmic-ray interactions with solar gas. While it is known that incoming cosmic rays must generally first be reflected by solar magnetic fields to produce outgoing gamma rays, theoretical…
The very-high-energy gamma-ray sky can be surveyed on a daily basis by particle-detector arrays at high (mountain) elevation. In the northern hemisphere the survey recently conducted by the HAWC gamma-ray observatory significantly enriched…
The strongly diverging magnetic field lines in the very inner heliosphere, through the associated magnetic focusing/mirroring forces, can, potentially, lead to highly anisotropic galactic cosmic ray distributions close to the Sun. Using a…
Cosmic rays represent one of the most important energy transformation processes of the universe. They bring information about the surrounding universe, our galaxy, and very probably also the extragalactic space, at least at the highest…
Galactic cosmic rays and solar energetic particles (SEPs) affect the performance of instruments carried on board space missions and are the source of the absorbed dose to astronauts. Particles above 100 MeV are the most penetrating. The…
Research in cosmic rays is now nearly a century old, but most of the fundamental questions in this field remain unanswered, on the other hand the perspectives of future studies in the next decade are very bright. New detectors will provide…