Estimating cosmic ray vertical cutoff rigidities as a function of the McIlwain [formula omitted]-parameter for different epochs of the geomagnetic field

Abstract

The McIlwain L-parameter is commonly used to estimate cosmic ray vertical cutoff rigidities. However, in some areas of the world, secular changes in the geomagnetic field between 1955 and 1980 have been large enough to produce significant differences in both the vertical cutoff rigidity and in the L value for specified positions. We show that these changes are complimentary, and that the relationship between the L value and the vertical cutoff rigidity is essentially invariant.