Pioneer 10 and 11 and Voyager 1 and 2 observations are used to study global aspects of the solar wind interaction with Jupiter and Saturn. Solar wind measurements before and after the encounters are used to determine average upstream flow parameters at 5 and 9 AU. Bow shock and magnetopause position are found to vary as the fourth root of dynamic pressure at Jupiter and the sixth root at Saturn. The average distances to the nose of the magnetopause based upon the Pioneer and Voyager boundary crossings for Jupiter and Saturn are 68 RJ and 19 RS, respectively, after correction for varying solar wind pressure. In shape, the Jovian bow shock and magnetopause surfaces are similar to their terrestrial counterparts, but the width of the magnetosheath is 45% less than predicted by axisymmetric gas dynamic theory. This result is interpreted as evidence for strong polar flattening of the Jovian magnetosphere. The Saturnian magnetopause and bow shock boundaries are significantly more flared than at the earth with a subsolar magnetosheath that is 20% thinner than predicted by gas dynamic theory. On the basis of these results it is suggested that Saturn is intermediate between the earth and Jupiter in terms of polar flattening, with the unusual flaring of the Saturn magnetopause being due to the low ratio of static to dynamic pressure in the distant heliosphere.

Models of the magnetospheric and magnetosheath magnetic fields are used to determine the relative orientations of these fields at the dayside magnetopause in order to locate potential merging sites. Areas on the magnetopause with different fractional antiparallel components are displayed by contour diagrams for a variety of interplanetary field orientations. For interplanetary fields oriented perpendicular to the solar wind velocity the areas of nearly antiparallel field agree with those obtained by Crooker using simplified representations for the magnetic field geometry. Here, the application of more realistic models gives the locations of areas where any antiparallel component occurs. Potential merging sites for interplanetary fields with radial components are also illustrated. The results suggest that the topology of the magnetosheath and magnetospheric fields provides antiparallel components over a substantial fraction of the magnetopause for most interplanetary field orientations.

A computational model has been developed for the determination of the gasdynamic and magnetic field properties of the solar wind flow around a magnetic planet, such as the earth, or a nonmagnetic planet, such as Venus. The procedures are based on an established single‐fluid, steady, dissipationless, magnetogasdynamic model and are appropriate for the calculation of axisymmetric, supersonic, super‐Alfvénic solar wind flow past a planetary magneto/ionosphere. Sample results are reported for a variety of solar wind and planetary conditions. Some of these are new applications; others are included to show that the new procedures produce the same results as previous procedures when applied to the same conditions. The new methods are completely automated and much more efficient and versatile than those employed heretofore.

Advanced computational procedures are applied to an improved model of solar wind flow past Venus to calculate the locations of the ionopause and bow wave and the properties of the flowing ionosheath plasma in the intervening region. The theoretical method is based on a single‐fluid, steady, dissipationless, magnetohydrodynamic continuum model and is appropriate for the calculation of axisymmetric supersonic, super‐Alfvénic solar wind flow past a nonmagnetic planet possessing a sufficiently dense ionosphere to stand off the flowing plasma above the subsolar point and elsewhere. Determination of time histories of plasma and magnetic field properties along an arbitrary spacecraft trajectory and provision for an arbitrary oncoming direction of the interplanetary solar wind have been incorporated in the model. An outline is provided of the underlying theory and computational procedures, and sample comparisons of the results are presented with observations from the Pioneer Venus orbiter.

This study uses observations by a number of spacecraft to investigate the asymptotic behavior of planetary bow shocks. Toward this end a single standard method has been used to model distant bow shock position and shape. Mach cone angles of 13.9±2°, 11.4±3°, and 8.1±4° at Venus, Earth, and Mars, respectively, were determined from the observational shock models. These cone angles and their decrease with growing distance from the sun are consistent with downstream bow shock position being limited by the MHD fast mode Mach number. Gas dynamic solutions for solar wind flow about Venus, Earth, and Mars were computed up to 50 ROB (i.e., obstacle radii) behind each planet and compared with observed bow shock location. In each case the position of the shock was well predicted up to a certain distance downstream: −4 ROB at Venus, −6 ROB at Earth, and −10 ROB at Mars. Beyond this point the observed shock position lies farther from the aberrated sun‐planet line than the gas dynamic model with the discrepancy greatest at Venus and least at Mars. The better agreement between gas dynamic theory and observation with growing distance from the sun is attributed to an increase in the accuracy of the gas dynamic approximation with decreasing IMF strength.