United States Department of Transportation
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Edition:Final
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Abstract:Primary cosmic radiation from both the Sun and interstellar space enters Earth's atmosphere in varying amounts. Outside of Earth's atmosphere, cosmic radiation is modulated by solar activity and Earth's magnetic field. Once the radiation enters Earth's atmosphere, it interacts with Earth's atmosphere in the same manner regardless of its point of origin (solar or galactic). CARI (i.e., the Civil Aviation Research Institute—the previous name of what is now the Civil Aerospace Medical Institute, or CAMI) software for calculating doses of ionizing radiation in the atmosphere from cosmic radiation has been in development at CAMI since the late 1980s. For CARI-6 and earlier versions, the approach used to calculate time- and location-dependent dose rates in the atmosphere consisted of interpolation from databases of precalculated galactic cosmic radiation dose rates covering a wide range of input conditions (latitude, longitude, solar activity, and altitude). These early databases were not appropriate for the calculation of solar proton event dose rates. They were also limited to 87,000 feet maximum altitude and increasingly inaccurate for effective doses at altitudes above 60,000 feet. This report presents the methods of calculating the cosmic radiation particle fluxes and doses in the atmosphere used in CARI-7 and -7A. The approach consists of building representative cosmic radiation shower contributions from a database of precalculated Monte Carlo simulations of particle entry into Earth's atmosphere. While somewhat slower than the older method, the new approach improves accuracy at high altitudes and is easily applied to galactic cosmic radiation and solar particle events. While CARI-7 handles the data in the most consistent with the Monte Carlo simulations, CARI-7A offers added options for users in handling these data.
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