Electrons in the cosmic radiation

Abstract

The nature of cosmic ray electrons and their radiation in the Universe has been studied. A convection associated diffusion model is proposed to describe the main characteristics of the large-scale distribution of cosmic ray electrons in the Galaxy: (1) a small Galacto-centric radial gradient; (2) spectral flattening with Galactic latitude; and (3) an extensive halo above the Disk. A new derivation of the interstellar radiation field indicates the existence of an inverse Compton γ -ray halo. This γ -ray halo can contribute up to 60% of the observed diffuse Galactic γ-ray flux at intermediate latitudes and also accounts for the spectral flattening with latitude. This result leads to a new estimate of the extragalactic γ -ray background flux. An energy equipaxtition theory is proposed for the global correlation between radio power and far-infrared luminosity for spiral galaxies, in which the dynamical role of cosmic rays in galactic evolution is implied. The model successfully explains the non-unity slope of the correlation and predicts the escape of cosmic ray electrons from our Galaxy. The interstellar flux of MeV cosmic ray electrons is derived from γ -ray data. The flux is found to be surprisingly high and a new type of source is required. The lower hybrid plasma instability initiated by stellar winds is suggested to be the acceleration mechanism. This high flux of electrons is sufficient to account for the interstellar ionization and heating in HI regions. Features of the local Galactic magnetic field are revealed by analysing pulsar rotation measure data. The large scale regular field is found to be in a bisymmetric configuration and to be stronger in the interarm region (3 µG) than in the arm region (1 µG). The derived small-scale irregular field is shown to have a dominant strength of 6 µG.