Pioneer 10 observations of the solar wind interaction with Jupiter

Abstract

Detailed analysis of the Pioneer 10 plasma analyzer experiment flight data during the Jupiter flyby in late November and early December 1973 has been performed. The observations show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger. Jupiter is found to have a detached standing bow shock wave of high Alfv6n Mach number. Like the earth, Jupiter has a prominent magnetopause that deflects the magnetosheath plasma and excludes its direct entry into the Jovian magnetosphere. Unlike that of the earth, the sunward hemisphere of Jupiter's outer magnetosphere is found to be highly inflated with thermal plasma and a high-beta region that is highly responsive to changes in solar wind dynamic pressure. Observational arguments are presented that tend to discount a thin disklike magnetosphere and to favor a Jovian magnetosphere, albeit one probably considerably flattened in comparison with the earth's magnetosphere, yet still with reasonable thickness. Results concerning the shock jump conditions, the magnetosheath flow field, and inferred internal magnetospheric plasma are presented. The Pioneer 10 spacecraft was successfully launched fromCape Kennedy on March 3, 1972, aboard an Atlas-Centaur launch vehicle that incorporated a TE-364-4 solid-propellant third stage. At the time, Pioneer 10 attained the highest injection energy ever achieved, as is attested to by the fact that the spacecraft required only 11 hours to cross the lunar orbit. After a 21-month flight the Pioneer 10 spacecraft arrived at its radius of closest approach at Jupiter at a distance of approximately 2.8 Rj (Jovicentric Jupiter radii) on December 4, 1973. The principal scientific objectives of Pioneer 10 are to investigate the nature of the interplanetary medium beyond the orbit of Mars, including the asteroid belt, and to make direct in situ observations of the planet Jupiter and its environment. The successful flyby of Jupiter by Pioneer 10 achieved the latter objectives; however, the interplanetary objectives are still being pursued in the present postencounter mission beyond Jupiter. Present estimates are that the Pioneer 10 spacecraft can be utilized for interplanetary observations to a solar radial distance of at least 20 AU. The Pioneer 10 spacecraft and trajectory details have been reported by Hall [1974] and are only briefly summarized here. The Pioneer 10 spacecraft weighs 258 kg, including 33 kg for the 11 on-board experiments. Two additional experiments are performed by using the spacecraft S band communications system. The spacecraft is spin-stabilized, having a spin rate of 4.8 rpm. The spacecraft spin axis is parallel to the axis of the 2.74-m-diameter high-gain antenna reflector and is kept pointed toward the earth in order to maximize the communication bit rate. The maximum bit rate used during the Jupiter encounter was 1024 bits/s. Spacecraft spin axis precession maneuvers are required periodically in order to maintain earth pointing an...

Pioneer-10 observation of the solar wind proton temperature heliocentric gradient

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Magnetic coordinates for the Pioneer 10 Jupiter encounter

“…A larger-scale view, showing the trajectory out to 250 R, is shown in Figure 3 of the paper by Wolfe et al.(1974). The asterisks show the position of the spacecraft at twohour intervals.…”

Magnetic field experiment for Voyagers 1 and 2

“…This view is based on the wide variation in the radial distances of the observed multiple bow shock and magnetopause crossings (Smith et al, 1974Wolfe et al, 1974). This is illustrated in Figure 1 by the Pioneer 11 magnetic field measurements .…”