Search Results

Galactic cosmic rays produce high-energy radiation fields in the atmosphere at aircraft altitudes. Energetic particles generated on the sun also bombard the earth from time to time. These particles also produce radiation fields at aircraft altitudes which have qualitatively the same properties as atmospheric cosmic rays. We have used transport theory to calculate atmospheric cosmic-ray quantities for verification and equivalent doses to aircraft crews. We have also calculated radiation doses from several large solar energetic particle events which took place in 1989. The spectra incident on the atmosphere were determined assuming diffusive shock theory.

Several large solar proton events occurred in the latter half of 1989. For a moderately shielded spacecraft in free space, the potential exposure would have been greatest for the flare which occurred between October 19 to 27, 1989. This flare was comparable to the large flare event of August 1972. The temporal variations of the proton energy spectra at approximately 1 AU were monitored by the GOES-7 satellite. These data, recorded and processed at the NOAA-Boulder Space Environment Laboratory, provide the opportunity to analyze dose rates and cumulative doses which might be incurred by astronauts in transit to, or on, the moon. Of particular importance in such an event is the time development of exposure in the early phases of the flare, for which dose rates may range over many orders of magnitude in the first few hours. Consequently, special attention is given to the early time variation of the dose rate.