AN EVALUATION OF MAGNETOSPHERIC B-FIELD MODELS BASED ON IMP-HEOS AND ISEE DATASETS

A new dataset comprising of more than 30,000 average magnetic field vectors measured by the ISEE spacecraft during 1977-1981 was used to generate magnetospheric magnetic field modeis similar to earlier ones based on IMP and HEOS data. First, a set of models was generated for the same Kp index intervals as those used in T87 and T89. A comparison between old and new models and their Kp-dependences showed them to be consistent, in spite of different time spans and spatial coverages of the datasets. Special attention was paid to the predicted Bz distribution in the near tail plasma sheet, of crucial importance for mapping the nightside poar ionosphere to the equatorial magnetosphere. While
models based on IMP-HEOS data generally agree well with those based on ISEE, the latter show a significantly larger Bz in the neutral sheet, in agreement wth recent analyses of ISEE data. Because simultaneous solar wind data are available for most of the ISEE data, we were able to create models for different ranges of the solai wind ram pressure Pdyn and IMF Bz. It was found in line with the results of Sibeck et al. that the average model magnetopause shrinks and expands self-similarly as Pdyn increases and decreases. However, we failed to find the strong IMF-related contol of the magnetopause shape reported by Sibeck et al.