Solar Particle Events
The map is divided into four regions based on the degree of geomagnetic shielding that air travelers are provided by the Earth's magnetic field. Region 1 is the polar-latitude region where the magnetic field provides little to no protection from solar cosmic radiation. The highest dose rates occur in Region 1. In the absence of a geomagnetic storm, dose rates in Region 2 will be lower than those in Region 1.

During a G5 geomagnetic storm, dose rates throughout Region 2 can be as high as those in Region 1. In Region 3, a total dose to the conceptus that exceeds the recommended limit is possible in a 10-hour exposure at 40- to 60-thousand feet, but dose rates will always be lower than in Regions 1 and 2. Dose rates in Region 4 never exceed a few percent of dose rates in Region 1. In Region 4, in the 20-year period January 1987 through December 2006, the highest 10-hour dose to the conceptus from solar cosmic radiation at 50,000 ft was 10% of the recommended limit.

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Downloadable version of Solar Radiation map shown below (PDF)