An Evaluation over the New Zealand Region of Candidate and Adopted Models for IGRF 1995

Abstract

Three candidate models for DGRF 1990 and three candidate models for IGRF 1995, two of which include models of the secular variation for 1995-2000, were evaluated by comparison with observations from throughout the New Zealand region. No candidate model stands out as being significantly better or worse than any other candidate model from the same category. UB-90 has the poorest fit to the vertical component (Z) for 1990 but has the best fit to the total intensity (F). IZ-95 has the poorest fit to both the east component (Y) and Z for 1995 and, as a consequence, to F also. The adopted model for IGRF 1995 (main field) differs less on average from updated values of Y and Z than does the adopted model for DGRF 1990, although the range of differences is greater for all components. The candidate models for secular variation underestimate the magnitude of the north component (X) by 5-9 nT/yr on average but fit Z (and F) well (within 2 nT/yr on average).