MODELING THE EARTHS MAGNETOSPHERIC MAGNETIC-FIELD CONFINED WITHIN A REALISTIC MAGNETOPAUSE

Empirical data-based models of the magnetospheric magnetic field have been widely used during recent years. However, the existing models (Ts yganenko, 1987, 1989a) have three serious deficiencies: (1) an unstabl e ''de facto'' magnetopause, (2) a crude parametrization by the K-p in dex, and (3) inaccuracies in the equatorial magnetotail B-z values. Th is paper describes a new approach to the problem; the essential new fe atures are (1) a realistic shape and size of the magnetopause, based o n fits to a large number of observed crossings (allowing a parametriza tion by the solar wind pressure), (2) fully controlled shielding of ti le magnetic field produced by all magnetospheric current systems, (3) new flexible representations for the tail and ring currents, and (4) a new ''directional'' criterion for fitting the model field to spacecra ft data, providing improved accuracy for field line mapping. Results a re presented from initial efforts to create models assembled from thes e modules and calibrated against spacecraft data sets.