In 1990’s Very High Energy Gamma-ray Astrophysics has dramatically advanced due to the Imaging Air Čerenkov Telescopes(IACTs). After the first detection of TeV gamma-ray emission from the Crab nebula in 1989, several type of TeV gamma-ray sources, Active Galactic Nuclei(AGN), young pulsar, and SuperNova Remnant(SNR), have been detected. In those discoveries, recent detections of both synchrotro...

Observations of cosmic-ray helium energy spectra provide important constraints on cosmic ray origin and propagation. However, helium intensities measured at Earth are affected by solar modulation, especially below several GeV/nucleon. Observations of helium intensities over a solar cycle are important for understanding how solar modulation affects galactic cosmic ray intensities and for separat...

A recent re-determination of the non-thermal component of the hard X-ray to soft γ-ray emission from the Galactic ridge, using the SPI instrument on the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) Observatory, is shown to be well reproduced as inverse-Compton emission from the interstellar medium. Both cosmic-ray primary electrons and secondary electrons and positrons contribute ...

The cosmic-ray propagation code GALPROP has recently been enhanced in the areas of Galactic magnetic field and synchrotron radiation. A full 3D treatment is now implemented. We describe these enhancements and show applications to the interpretation of non-thermal radio surveys and gamma rays, to probe the Galactic cosmic-ray electron spectrum and magnetic fields.

In an attempt to explain the observed unexpectedly high energy gamma radiation over a broad region of the galactic plane in the general direction of the galactic center, a model is proposed wherein the galactic cosmic rays are preferentially located in the high matter density regions of galactic arm segments, as a result of the weight of the matter in these arms tieing the magnetic fields and h...

We apply a wind model, driven by combined cosmic-ray and thermal-gas pressure, to the Milky Way, and show that the observed Galactic diffuse soft X-ray emission can be better explained by a wind than by previous static gas models. We find that cosmic-ray pressure is essential to driving the observed wind. Having thus defined a “best-fit” model for a Galactic wind, we explore variations in the b...

Particle acceleration at supernova remnant (SNR) shock waves is regarded as the most probable mechanism for providing Galactic cosmic rays at energies below 10 eV. The Galactic cosmic ray hadron component would in this picture result from the injection of relativistic particles from many SNRs. It is well known that the superposition of individual power law source spectra with dispersion in the ...

The study of Galactic diffuse γ radiation combined with the knowledge of the distribution of the molecular hydrogen in the Galaxy offers a unique tool to probe the cosmic ray flux in the Galaxy. A methodology to study the level of the cosmic ray "sea" and to unveil target-accelerator systems in the Galaxy, which makes use of the data from the high resolution survey of the Galactic molecular clo...

The origin of Galactic cosmic rays is still a burning question that forms a major motivation for developments in ground-based gamma-ray astronomy. SNRs are long-thought to be sites for the acceleration of Galactic cosmic rays, and evidence for gamma-ray and non-thermal X-ray production from some SNRs suggest that they may be capable of accelerating particles to multi-TeV energies. Yet, along wi...

We investigate the problem of transition from galactic cosmic rays to extragalactic ultra high energy cosmic rays. Using the model for extragalactic ultra high energy cosmic rays and observed all-particle cosmic ray spectrum, we calculate the galactic spectrum of iron nuclei in the energy range 108 − 109 GeV. The flux and spectrum predicted at lower energies agree well with the KASCADE data. Th...