High energy cosmic-ray electrons beyond 100 GeV

Abstract

High energy cosmic-ray electrons lose their energy by synchrotron and inverse Compton processes during their propagation through the Galaxy. Then the electron spectrum brings us a unique information for the sources and propagation of cosmic-rays, and many observations have been carried out since the first discovery of cosmic-ray electrons. Beyond 100GeV, however, only a few measurements were successful to observe the absolute flux of electrons. The emulsion chamber observations were the most successful to observe the spectrum extending up to a few TeV region in collaborating with University of Washington group. Beyond 100GeV, the statistical accuracy of observed data is still limited, and we spent efforts to accumulate the data by improving the methods of detection of electrons particularly in a few hundred GeV region. We report here the results based on the new flight exposures of chambers 1996 and 1998. The statistical accuracy of electron spectrum was much improved at several hundred GeV. Our old spectrum is still consistent with the new data. The results and improvements to the observations of those high energy electrons, and their astrophysical significance are presented.