Scintillation-counter observations of auroral X rays during the geomagnetic storm of May 12, 1959

Auroral X rays were observed at 10 g/cm2 atmospheric depth over Minneapolis on May 12, 1959, with a balloon-borne NaI scintillation spectrometer in the energy range 22 to 263 kev. This event accompanied the low-energy solar cosmic rays that also produced some γ rays in the atmosphere. Energy spectra of the X rays were obtained after correcting for the presence of these γ rays. The peak in the auroral X-ray intensity was found to be associated with the passage of the aurora at the zenith. The electron spectrum responsible for the X rays has been determined and found to be in agreement with the observations of electron spectrum of the outer radiation belt.