Atmospheric electron spectrum above 30 GeV at the high altitude

Abstract We have observed the primary electron spectrum from 30 GeV to 3 TeV using emulsion chambers flown by balloons at the top of the atmosphere, for the purpose of exploring the origin of cosmic raysin the Galaxy. The atmospheric gamma rayshave been simultaneously observed in the 30 GeV–8 TeV energy range. In this paper, we estimate the atmosphericelectron spectrum in the upper atmosphere( 2 ) from our observed gamma-rayspectrum using the electromagnetic shower theory in order to derive the primary cosmic-rayelectron spectrum. The transport equations of the electron and gamma-rayspectrum are analytically solved and the results are compared with those of Monte Carlo simulation (MC). Since we used the observed atmospheric gamma raysas the source of atmosphericelectrons, our solutions are free from ambiguities on the primary cosmic-raynuclear spectra and nuclear interaction models included in MC. In the energy range above several hundred GeV, the Dalitz electrons produced directly from neutral pions contribute around 10% to the whole atmosphericelectron spectrum at the depth of 4 g/cm 2 , which increases in importance at the higher altitude and cannot be ignored in TeV electron balloon observations.