A GENERALIZED HINGED-MAGNETODISC MODEL OF JUPITER NIGHTSIDE CURRENT SHEET

For each of the three spacecraft that have visited the magnetotail of Jupiter, independent hinged-magnetodisc models have bern constructed for Jupiter's nightside current sheet. Model parameters (especially the hinge point distance) derived from any one encounter were found to be inapplicable to data from other encounters. For example, for the Pioneer 10 current sheet crossings, Goertz (1976, 1979) found that the current sheet does not significantly bend away from the dipole magnetic equator. On the other hand, Behannon et al. (1981) and Goertz (1981) found it necessary to introduce hinging of the current sheet in their models near a cylindrical radial distance of 60 R(J) for Voyager 1 observations. The hinge distance was found to be even smaller (approximately 40 R(J)) for Voyager 2 by Behannon et al. (1981). Vasyliunas and Dessler (1981) have criticized hinged magnetodisc models for their failure to organize current sheet crossing data from all three of the spacecraft by using a single set of parameters. Khurana and Kivelson (1989) in a study that evaluated several models of Jupiter's current sheet pointed out that if the hinging of the magnetotail is caused by solar wind forcing then the hinging distance should be parameterized in terms of Jupiter-Sun-magnetospheric (JSM) x coordinate instead of the cylindrical (or planetocentric) radial distance. In this paper we develop a quantitative hinged-magnetodisc generalized model that incorporates this suggestion and explains the current sheet crossing data from all three of the flybys with the introduction of only three fitting parameters. The present model is comparable to or slightly superior than the models published previously in terms of rms error of fit between the modeled and observed current sheet crossing locations. The added novelty is that unlike the previous models the generalized model does not require a different set of parameters for each of the three encounters. A comparison of our results with the earlier models is presented.