AN EMPIRICAL-MODEL OF THE SIZE AND SHAPE OF THE NEAR-EARTH MAGNETOTAIL

A model of the size and shape of the near-earth magnetotail which depends upon distance downtail, rhov2sw, and IMF B(z) has been developed. This empirical model was developed by first using observations of the magnetic field in the lobe by ISEE-1 and simultaneous observations of the magnetic field and plasma properties of the solar wind by IMP-8 to determine the flaring angle of the near-earth magnetotail in the region -22.5 R(e) less-than-or-equal-to x less-than-or-equal-to -10 R(e). These studies show that the flaring angle depends on x, rhov2sw, and IMF B(z). In particular, the median flare angle increases linearly with decreasing B(z) when the IMF is southward, while the flare angle is constant when the IMF is northward. The empirical function derived for the flaring angle of the magnetotail is used to determine a relation for the radius of the tail.