Solar Radiation Alert System

The Solar Radiation Alert (SRA) system continuously evaluates measurements of high-energy protons made by instruments on GOES satellites. If the measurements indicate a substantial elevation of effective dose rates at aircraft flight altitudes, the Civil Aerospace Medical Institute issues an SRA via the National Oceanic and Atmospheric Administration Weather Wire Service. This report describes a revised SRA system. SRA issue-criteria remain the same but significant improvements have been made in the calculations. The solar proton fluence to effective dose conversion coefficients have been recalculated using 2007 recommendations of the International Commission on Radiological Protection and the latest release of the Monte Carlo transport code, MCNPX 2.6.0. The shape of the 10 MeV secondary neutron spectrum is now accounted for down to 100 eV. The flux correction based on spectral index has been revised to smooth the flux spectrum of solar protons. Estimates of the 605 MeV spectral shape have been improved by the addition of correction factors for the differential interpretation of the 700 MeV integral flux channel. Estimates of galactic cosmic radiation background count rates in the GOES data are now median rather than mean values. Estimated solar cosmic radiation dose rates are about 10 times higher than those made using the previous version of the SRA system. This work was accomplished under approved task TOXLAB.AV9000 1208AC086110 Prepared in cooperation with National Geophysical Data Center, NOAA, Boulder.