Related papers: The Galactic cosmic-ray Sun shadow observed by HAW…
Cosmic rays reaching the atmosphere of an astrophysical object produce showers of secondary particles that may then escape into space. Here we obtain the flux of gamma rays and neutrinos of energy $E>10$ GeV emitted by the Sun, Jupiter and…
I characterize the global distribution of the 3/4 keV band background with a simple model of the hot Galactic corona, plus an isotropic extragalactic background. The corona is assumed to be approximately polytropic (index = 5/3) and…
The injection of ultra-high energy cosmic rays in the intergalactic medium leads to the production of a GeV-TeV gamma-ray halo centered on the source location, through the production of a high electromagnetic component in the interactions…
The field of ultra-high energy cosmic rays made a lot of progresses last years with large area experiments such as the Pierre Auger Observatory, HiRes and the Telescope Array. A suppression of the cosmic ray flux at energies above…
Energetic gamma rays (GeV to TeV photon energy) have been detected toward several supernova remnants (SNR) that are associated with molecular clouds. If the gamma rays are produced mainly by hadronic processes rather than leptonic processes…
Cosmic rays are charged energetic particles that permeate the interstellar medium. Their sizeable energy share and penetration power makes them essential players in the dynamical and chemical processes that rule Galactic evolution, such as…
Hadronic cosmic particles (cosmic rays) and gamma rays are constantly absorbed in the Earth's atmosphere and result in air showers of secondary particles. Cherenkov radiation from these atmospheric events is used to measure cosmic gamma…
The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the…
Measurements of cosmic rays by experiments such as ATIC, CREAM, and PAMELA indicate a hardening of the cosmic-ray energy spectrum at TeV energies. In our recent work (Thoudam & H\"orandel 2012a), we showed that the hardening can be due to…
The Sun is a main source of high energy neutrinos. These neutrinos appear as secondary particles after the Sun absorbs high-energy cosmic rays, that find there a low-density environment (much thinner than our atmosphere) where most…
Adopting a recent calculation of the Galactic interstellar radiation field, we calculate the attenuation of the very high energy gamma rays from the Galactic sources. The infra-red radiation background near the Galactic Center is very…
Gamma-ray bursts (GRBs) are among the most luminous sources in the universe and the nature of their emission up to very high energy is one of the most important open issue connected with the study of these peculiar events. The High Altitude…
Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona. Both high-resolution observations and magnetoconvection simulations show the ubiquitous presence of magnetic fields on the…
The High Altitude Water Cherenkov (HAWC) observatory is a ground-based air-shower detector designed to study the TeV gamma and cosmic ray windows. The observatory is composed of a densely packed array of $300$ water Cherenkov tanks, $4.5$ m…
Atmospheric Cerenkov telescopes are used to detect electromagnetic showers from primary gamma rays of energy > 300 GeV and to discriminate these from cascades due to hadrons using the shape and orientation of the Cerenkov images. The…
The elemental composition of the Sun's hot atmosphere, the corona, shows a distinctive pattern that is different than the underlying surface, or photosphere (Pottasch 1963). Elements that are easy to ionize in the chromosphere are enhanced…
Magnetic fields in the upper atmospheres of solar-like stars are believed to provide an enormous amount of energy to power the hot coronae and drive large-scale eruptions that could impact the habitability of planetary systems around these…
Cosmic rays (CRs) generate diffuse emission while interacting with the Galactic magnetic field (B-field), the interstellar gas and the radiation field. This diffuse emission extends from radio, microwaves, through X-rays, to high-energy…
Large- or medium-scale cosmic ray anisotropy at TeV energies has not previously been confirmed to vary with time. Transient anisotropy changes have been observed below 150 GeV, especially near the passage of an interplanetary shock and…
The majority of Galactic TeV gamma-ray sources are pulsar wind nebulae (PWNe) and supernova remnants (SNRs), and the most common association for unidentified sources is PWN. Many of these sources were discovered in TeV by imaging air…