Accession Number : ADA018096

Title :   A Comparison of Vertical Cosmic-Ray Cutoff Rigidities as Calculated with Different Geomagnetic Field Models.

Descriptive Note : Interim rept.,

Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MASS

Personal Author(s) : Shea,M. A. ; Smart,D. F.

Report Date : 26 NOV 1975

Pagination or Media Count : 8

Abstract : The calculated values of cutoff rigidities determined by the trajectory-tracing technique are dependent upon which geomagnetic field model is used. In the past 20 years a number of geomagnetic field models have become available. In general each model is derived to fit the magnetic field data appropriate to a specific epoch with some of the more recent models containing time derivatives so that the models are applicable over a number of years. In the past the applicability of some models has been questioned inasmuch as small, but nevertheless significant, differences in vertical cutoff rigidities have been calculated with the different field models. The authors have used the time derivatives of the International Geomagnetic Reference Field model to calculate a selected set of vertical cutoff rigidities appropriate for Epoch 1955.0 and find that in general these values compare favorably with the results previously obtained using the Finch and Leaton 1955.0 field model. From these results and other epoch comparisons, it is found that vertical cutoff rigidities are essentially the same when calculated using comparable field models for the same epoch.

Descriptors :   *Cosmic rays, *Geomagnetism, Mathematical models, Computations

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE