Abstract
In the extremely low density plasmas in the Universe, the energy distribution of electrons starts to deviate from Maxwellian distribution, when acceleration processes, such as the Fermi acceleration process are operative with a magnetic field moving at high velocity. Radiation from these electrons is expected in the X-ray wave band by synchrotron radiation and by inverse-Compton scattering. Supernova remnants and clusters of galaxies exhibit thermal emission from hot plasmas of several keV as well as non-thermal power law components above 20 keV, which suggests that the acceleration process takes place. A new hard X-ray imaging telescope system is also presented.
