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Atmospheric Gamma-Ray Lines Produced by Cosmic Rays and Solar Energetic Particles

G.H. Share, R.J. Murphy and E. Rieger

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We describe observations of atmospheric gamma rays produced by interactions of both cosmic rays and solar-energetic particles. The quiescent atmospheric spectrum produced by cosmic radiation was accumulated by the Solar Maximum Mission (SMM) spectrometer over its full 9-year lifetime. These observations are compared with a remarkable event observed by the spectrometer at about 1600 UT on 1989 October 20 during an intense solar energetic particle event at the Earth. The particle event followed an intense X-ray flare and coronal mass ejection that had occurred on the previous day. Twenty-three line features were identified from this event and twenty four were observed from the quiescent atmosphere. We compare the energies, widths and intensities of the different lines in both these spectra and discuss their origins.