B.6 ESP solar proton model specification

The ESP model [RN.15], (first published in [RD.146]; referred to in 9.2.2) provides a technique to compute the percentile of the distribution of cumulated solar proton fluence. It is based on an explicit formula for the probability of exceeding a given fluence ϕ of protons with energy above E, over a duration T:

(B-10)

with

(B-11)

and

(B-12)

where

Ф_RV and Ф_mean are respectively the relative variance and the mean of 1 year averaged proton fluence at 1 AU from the sun in the corresponding energy range.

The values for Ф_RV and Ф_mean for different energy ranges during solar maximum are given in Table B-7 and Table B-8.

The parameter values given in Table B-7 and Table B-8 have been calculated at NASA for periods during solar active years. The latest update of these parameters, which are used for these tables, dates from 14 Nov. 2002.

The extension to higher energy (up to > 300 MeV) is done through using the probability parameters for the > 100 MeV fluence, ϕ (>100 MeV), and scaling the fluence according to Table B-8.

Tabulated values of the proton fluence as obtained from the ESP model for different confidence levels are given in Table I-3.