9.2.4 Geomagnetic shielding

a. The minimum energies, i.e. cut-off energies, necessary for ions to penetrate to a geographic location shall be calculated with one of the following methods:

¾ Størmer’s theory [RN.20]

¾ MAGNETOCOSMICS [RN.21]

¾ The method given by Smart and Shea in [RN.22]

¾ Stassinopoulos & King: no geomagnetic shielding for McIlwain L-shells greater than 5 R_E[RN.23]

¾ No geomagnetic shielding for a conservative estimate.