Data are presented on the gamma rays emitted from the atmosphere to satellite altitudes in the absence of bremsstrahlung X rays associated with electron precipitation from the radiation belts. The measurements (40 keV to 2.7 MeV) were performed with a high‐resolution germanium spectrometer on board the polar‐orbiting satellite 1972‐076B. With the collimated spectrometer on the spinning vehicle (5‐s period) it was possible to separate sensor and vehicle backgrounds from the atmospheric and diffuse cosmic contributions. The atmospheric component was obtained by unfolding published values for the diffuse cosmic spectrum. Owing to variances in the measured values of the diffuse cosmic spectrum the uncertainties in the atmospheric gamma ray spectrum are greater near the equator and at lower energies than over the polar caps and/or at higher energies, where the atmospheric gamma rays dominate, and the errors in the atmospheric spectrum associated with the diffuse component are small. The variations of the atmospheric gamma rays with invariant latitude are presented. Over the polar caps the energy spectra are similar to those observed near the magnetic equator, and the intensities are higher by about a factor of 4. The spectral indices for least squares power law fits to the continuum are −1.34 ± 0.03 and −1.39 ± 0.08 for the polar cap and equatorial regions, respectively. A search was made for gamma ray lines emitted from the atmosphere in addition to the 511‐keV annihilation line. Several peaks were observed in the background spectrum, but no other lines were seen to be emitted from the atmosphere with a significant intensity.

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This is a preliminary report of the first satellite observations that have been made of the intensities and energy spectra of the bremsstrahlung >50 keV produced in the atmosphere by intense widespread precipitations of energetic electrons from the outer radiation belt. The measurements afford the opportunity to investigate nearly simultaneously the energetic electron behavior on a worldwide scale during magnetic disturbances. With such a technique, one may study different features of the precipitation processes than those covered by satellite‐borne particle detectors, which can provide more detailed particle information in a local region but without simultaneous measurements from many satellites can provide worldwide particle precipitation information only from long‐term statistical studies. The observations are made with a 50‐cm³ Ge(Li) gamma ray spectrometer that was launched aboard the spin‐stabilized satellite 1972–076B into a nearly circular polar orbit at 750‐km altitude on October 2, 1972. Correlative measurements of precipitating electrons are also made with an energetic electron spectrometer on board the same satellite. The longitude and hence local time extents of the precipitations are derived by least square fitting techniques from the gamma ray spectrometer responses at various spin angle orientations and satellite locations. The observations indicate the occurrence of nearly simultaneous precipitations over a wide range of local times. Significant variations occur in the intensity versus local time, but in the limited number of cases studied to date the intensities near noon are generally greater than those in the early morning hours.

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