Exposure to cosmic radiation and solar energetic particles

Full text: Several investigations of the radiation field at aircraft altitudes have been undertaken during solar cycle 23 which occurred in the period 1993-2004. The radiation field is produced by the passage of galactic cosmic rays and their nuclear reaction products as well as solar energetic particles through the earth's atmosphere. Galactic cosmic rays reach a maximum intensity when the sun is least active and are at maximum intensity during solar maximum period. During solar maximum an increased number of coronal mass ejections and solar flares produce high energy solar particles which can also penetrate down to aircraft altitudes. lt is found that the very complicated field resulting from these processes varies with altitude, latitude and stage of solar cycle. By employing several active and passive detectors, the whole range of radiation types and energies were encompassed. Calibration and intercomparisons were carried out at many of the most advanced particle accelerators available internationally. In-flight data was obtained with the co-operation of many airlines and NASA, providing information over a wide range of altitudes and latitudes covering the whole of solar cycle 23. The inflight data base was used for comparison with the predictions of various computer codes. The main results of these investigations will be discussed and their impact on civil aircrew and frequent travellers will be addressed. A brief outline of some recent studies of exposure to radiation in earth orbit will conclude this contribution. (author)