NEW INTERPLANETARY PROTON FLUENCE MODEL

A new predictive engineering model for the interplanetary fluence of protons with energies > 10 MeV and > 30 MeV is described. The data set used is a combination of observations made from the Earth’s surface and from above the atmosphere between 1956 and 1963 and observations made from spacecraft in the vicinity of Earth between 1963 and 1985. The data cover a time period three times as long as the period used in earlier models. With the use of this data set the distinction between “ordinary proton events” and “anomalously large events” made in earlier work disappears. This permitted the use of statistical analysis methods developed for “ordinary events” on the entire data set. The > 10 MeV fluences at 1AU (astronomical unit) calculated with the new model are about twice those expected on the basis of models now in use. At energies > 30 MeV, the old and new models agree. In contrast to earlier models, the results do not depend critically on the fluence from any one event and are independent of sunspot number. Mission probability curves derived from the fluence distribution are presented. © 1989 American Institute of Aeronautics and Astronautics, Inc. All rights reserved. All Rights Reserved.