B-Lspace and geomagnetic field models

We have intercompared geomagnetic field models in B-L space for 0.20 ≤ B ≤ 0.24 gauss and 1.2 ≤ L ≤ 1.8 RE (earth radii). Three field models were selected because of their general usage in the analysis of trapped radiation data: Jensen and Whitaker (569 coefficient); Jensen and Cain (48 coefficient); GSFC (9/65) (99 coefficient). These models were compared with the GSFC (12/66) field model (120 coefficient). The geographic coordinates of constant B-L traces were computed, using the GSFC (12/66) field in both the southern and northern hemispheres. At each geographical point along the traces thus defined, B and L values were recalculated, using different geomagnetic field models. We find that variations in B-L space of the 48- and 569-coefficient models with respect to the 120-coefficient model are great enough to cause significant ambiguities in flux contours of the trapped radiation. We also have examined the effects of temporal variations of the geomagnetic field on B-L space. The uncertainties in the proton flux contours in B-L space caused by errors in the field models and time variations of the geomagnetic field demonstrate the need for careful re-evaluation of existing data that pertain to possible time variations of inner-belt protons. The GSFC (12/66) appears to be sufficiently accurate to undertake such re-evaluation.