A New Jovian Magnetospheric Field Model for Galileo and Jupiter Icy Moon Orbiter (JIMO) Missions

Global magnetic field models are required to interpret field and plasma observations collected by Galileo in Jupiter's magnetosphere. Accurate models would also be needed to define the changing magnetic field in the rest frames of the icy satellites for the JIMO mission. Previous models have been inadequate because of simplifying assumptions or inadequate data coverage. We have recently developed a new model of Jupiter's magnetospheric field which borrows from techniques and methods developed by modelers for the earth's magnetospheric field. The model uses observations from all of the six spacecraft that have traveled through Jupiter's magnetosphere. The model incorporates an internal spherical harmonic model (VIP4), new modules for ring and magnetotail currents and shielding fields from an axially symmetric magnetopause. The structural model of the current sheet incorporates the delay and hinging of the current sheet observed at large distances. The thickness of the current sheet is modeled as a sinusoidal function of local time such that the current sheet is at its thinnest in the dawn sector and is the thickest in the dusk sector. The model also correctly includes the effect of the 3.2 degrees tilt between the Jovian orbital and equatorial planes We use Tsyganenko and Peredo [1994] models of disk-shaped current sheets to model the magnetic field of Jupiter's current sheet. The delay and hinging of the current sheet is introduced by using the general deformation technique [Tsyganenko, 1998]. The shielding field from the magnetopause for the equatorial current sheet and the internal field is specified by Cartesian and cylindrical harmonics, respectively. Comparisons of the model with observations are presented from various local times in Jupiter's magnetosphere.