No abstract

An equatorial sheet current deduced from Pioneer 10 magnetic field observations has been added to a planetary dipole field to construct a model of magnetic field due to sources inside the magnetopause.This internal field has then been used to calculate the magnetopause•surface in a cyclic process to a fifth order, in cycles, at which the calculation converges.The resulting magnetopause is considerably flatter in shape than one resulting from a primarily dipole internal field source.The field internal and external to the magnetopause surface due to the currents on the surface has been computed by integrating over the entire magnetopause.A model for the total magnetospheric field of the inflated magnetosphere has been constructed by adding this latter contribution to the internal source fields to obtain a global model of an inflated Jovianlike magnetospheric field.

We construct an idealized three‐dimensional model of Saturn's magnetosphere. The total magnetospheric field is a sum of three contributions; the first two contributions are internal, in the form of a planetary dipole and an equatorial ring current deduced from Voyager observations. We concentrate on the third contribution, resulting from the interaction of the solar wind with the Kronian magnetosphere. From the balance between the solar wind ram pressure and the magnetospheric pressure, we provide simultaneously models of the magnetopause and of the magnetic field due to the surface currents on the magnetopause. The resulting magnetopause has characteristics intermediate between those of analogous Earth and Jupiter magnetospheric models. A natural day‐night asymmetry arises in the total magnetospheric field. Its intensity is tested with Voyager 1 data: the third contribution improves the agreement between data and models in the outer magnetosphere. This work extends the range of a physically reliable model of Saturn's magnetosphere in latitudinal and longitudinal directions from regions where there have been observations to regions where there have not. We discuss several possible applications, particularly some relevant to the future Cassini mission.

We report on an idealized three‐dimensional model of Saturn's magnetopause. Using the subsolar point distance R0 = 24 RS, we provide an analytical parameterization of the magnetopause model described by Maurice and Engle [1995]. This representation of Saturn's magnetopause is consistent with Voyager 1 magnetopause crossing observations. The magnetopause shape is then scaled to 17 RS ≤ R0 ≤ 45 RS and applied to Pioneer 11 and Voyager 2 observations. Results highlight variations of R0 during magnetopause crossings (over a few hours) and/or between inbound and outbound crossings (over a few days). Finally, we extend the parameterization of Saturn's magnetopause to nonzero dipole tilt angles. The model is intended for use in support of the Cassini mission.

Magnetic observations which are not complicated by currents of trapped plasma are a good test of geomagnetopause and geomagnetotail predictions. Recent attempts to model the Hermean magnetospheric field based on a planet‐centered magnetic multipole field with a quadrupole moment in addition to the planetary dipole field or a dipole field linearly displaced from planet center and no quadrupole moment have produced reasonably good fits to the Mercury magnetic field measurements. In this work we find a better fit for a dipole displacement from the planet center by making use of an improved representation of the magnetic field in the magnetotail, where many of the Mercury measurements were made. The rms deviation of the data was reduced from 10. or 11. γ to 9.3 γ by employing this new tail field representation. Also, by making use of this new tail field representation, we find a best fit for a dipole displacement of −0.0285 RM (earlier, 0.026 RM) toward the dawn in the magnetic equatorial plane and 0.17 RM (earlier, 0.189 RM (earlier, 0.189 RM) northward along the magnetic dipole axis, where RM is the planet radius. Thus with only minor adjustments in the displacement vector of the dipole from the planet center we achieve a measurable improvement in the fit of the data by using the improved magnetotail field representation.