Data obtained by the Pioneer 10 vector helium magnetometer are presented along with models of the intrinsic magnetic field of JupiteL and its magnetosphere. Data acquired between 2.84 and 6.0 Rj, where the intensity of the planetary field ranged between 1900 and 18,400 'y, were used to develop a six-parameter eccentric dipole model of the field. The dipole so derived has a moment of 4.0 G Rfi and a tilt angle With respect to Jupiter's rotation axis of 11 ø. The system I!I (epOch 1957) longitude of the magnetic pole in the northern hemisPhere,•which is a north-seeking pole, is 222 ø. The dipole is displaced from the center of Jupiter by 0.11 Ra in the direction of iatitude 16 ø and system ili longitude 176 ø. The dipole tilt and the longitude of the pole ar e in goød agreement with values inferred from radio astronomy measurements. The magnetic moment and the offset derived from the Pioneer measurements represent a significant improvement in our knowledge of the planetary field. A model of the Jovian magnetosphere is presented in which the essential feature is an eastward current sheet that forms an annulus with Jupiter at the center. At Iarge distances from the planet the current sheet is nearly parallel to Jupiter's equator but, in general, does not lie in it. The Current sheet is warped, so that it is above the equator on one side and below it on the other. The current Sheet rotates with the planet, more or less lik e a rigid body; this behavior causes an apparent up and down motion and periodic crossings of the current sheet by Pioneer. The origin of the current sheet appears to be the very large centrifugal force, associated with Jupiter's great size and rapid rotation, acting on trapped low-energy magnetospheric plasma. The density of this plasma is estimated to be approximately 1 particle cm -3. A retrograde spiraling of field lines out of meridian planes is also observed, presumably as a result of azimuthal drag forces exerted on the outer magnetosphere. INSTRUMENT DESCRIPTION The magnetometer on board Pioneer !0 is an advanced version of the vector helium magnetometer previously used on the Mai'iner 4 and 5 missions to Mars and Venus [Slocum and Reilly, 1963; Connor, 1968]. The essential elements of the magnetometer include a helium lamp, a circular polarizer, a helium absorption cell, ß Helmholtz coils, a lens, and an !R detector. The basic operation of the instrument depends upon the effect of the magnetic field direction on the efficiency with which metastable helium can be optically pumped. The presence of an ambient magnetic field causes a sine wave modulation of the IR radiation passing through the gas cell at the fundamental frequency of the applied circular sweep field. The sensor output consists of the nulling currents that are applied in order to cancel this field 'signal.'The magnetometer measures the three field components over a frequency range from 0 to 10 Hz. At encounter the data rate was 1024 bits/s and the magnetometer sampling rate, corresponding to one vector measurement every 3/16 s, ...

During the time period 1961–1972, 11 magnetometers were sent to the moon. The primary purpose of this paper is to review the results of lunar magnetometer data analysis, with emphasis on the lunar interior. Magnetic fields have been measured on the lunar surface at the Apollo 12, 14, 15, and 16 landing sites. The remanent field values at these sites are 38, 103 (maximum), 3, and 327 γ (maximum), respectively. Simultaneous magnetic field and solar plasma pressure measurements show that the Apollo 12 and 16 remanent fields are compressed during times of high plasma dynamic pressure. Apollo 15 and 16 sub‐satellite magnetometers have mapped in detail the fields above portions of the lunar surface and have placed an upper limit of 4.4 × 1013 G cm³ on the global permanent dipole moment. Satellite and surface measurements show strong evidence that the lunar crust is magnetized over much of the lunar globe. Magnetic fields are stronger in highland regions than in mare regions and stronger on the lunar far side than on the near side. The largest magnetic anomaly measured to date is between the craters Van de Graaff and Aitken on the lunar far side. The origin of the lunar remanent field is not yet satisfactorily understood; several source models are presented. Simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole moon hysteresis curve from which the global lunar permeability is determined to be µ=1.012±0.006. The corresponding global induced dipole moment is ∼2 × 1018 G cm³ for typical inducing fields of 10−4 G in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5±2.0 wt%. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) is calculated for two assumed compositional models of the lunar interior. For a free iron/orthopyroxene lunar composition the total iron content is 12.8±1.0 wt%; for a free iron/olivine composition, total iron content is 5.5±1.2 wt%. Other lunar models with a small iron core and with a shallow iron‐rich layer are also discussed in light of the measured global permeability. Global eddy current fields, induced by changes in the magnetic field external to the moon, have been analyzed to calculate lunar electrical conductivity profiles by using several different analytical techniques. From night side transient data, ranges of conductivity profiles have been calculated. At a depth of 250 km into the moon, the conductivity ranges between 1 × 10−4 and 2 × 10−3 mhos/m. Thereafter, conductivity rises with depth and ranges between 2 × 10−3 and 8 × 10−2 mhos/m at 1000 km depth. Harmonic analyses of day side data are similar to night side results except at the greater lunar depths, where harmonic day side profiles show lower conductivities than the night side results do. Transient response analysis has recently been applied to data measured in the lobes of the geomagnetic tail, and thus calculation is allowed of a conductivity profile that increases with...

The Pioneer Saturn vector helium magnetometer has detected a bow shock and magnetopause at Saturn and has provided an accurate characterization of the planetary field. The equatorial surface field is 0.20 gauss, a factor of 3 to 5 times smaller than anticipated on the basis of attempted scalings from Earth and Jupiter. The tilt angle between the magnetic dipole axis and Saturn's rotation axis is < 1°, a surprisingly small value. Spherical harmonic analysis of the measurements shows that the ratio of quadrupole to dipole moments is < 10 percent, indicating that the field is more uniform than those of the Earth or Jupiter and consistent with Saturn having a relatively small core. The field in the outer magnetosphere shows systematic departures from the dipole field, principally a compression of the field near noon and an equatorial orientation associated with a current sheet near dawn. A hydromagnetic wake resulting from the interaction of Titan with the rotating magnetosphere appears to have been observed.

The Pioneer 11 vector helium magnetometer provided precise, contititious measurements of the magnetic fields in interplanetary space, inside Jupiter's magnetosphere, and in the near vicinity of Jupiter. As with the Pioneer 10 data, evidence was seen of the dynanmic interaction of Jupiter with the solar wind which leads to a variety of phenomena (bow shock, upstream waves, nonlinear magnetosheath impulses) and to changes in the dimension of the dayside magnetosphere by as much as a factor of 2. The magnetosphere clearly appears to be blunt, not disk-shaped, with a well-defined outer boundary. In the outer magnetosphere, the magnetic field is irregular but exhibits a persistent southward component indicative of a closed magnetosphere. The data contain the first clear evidence in the dayside magnetosphere of the current sheet, apparently associated with centrifugal forces, that was a donminatnt feature of the outbound Pionieer 10 data. A modest westward spiraling of the field was again evident inbound but not outbound at higher latitudes and nearer the Sun-Jupiter direction. Measurements near periapsis, which were nearer the planet and provide better latitude and longitude coverage than Pioneer 10, have revealed a 5 percent discrepancy with the Pioneer 10 offset dipole mnodel (D(2)). A revised offset dipole (6-parameter fit) is presented as well as the results of a spherical harmonic analysis (23 parameters) consisting of an interior dipole, quadrupole, and octopole and an external dipole and quadrupole. The dipole moment and the composite field appear moderately larger than inferred from Pioneer 10. Maximum surface fields of 14 and 11 gauss in the northern and southern hemispheres are inferred. Jupiter's planetary field is found to be slightly more irregular than that of Earth.

Pioneer 11 vector helium magnetometer observations of Saturn's planetary magnetic field, magnetosphere, magnetopause, and bow shock are presented. Models based on spherical harmonic analyses of measurements inside 8 Rs reveal that the planetary field has a high degree of symmetry about the rotation axis. The vector dipole moment of 0.2 G Rs³ has a tilt angle less than 1° and is offset along the polar axis 0.04±0.02 Rs. Equatorial offsets derived from the models show substantial variability and could be consistent with a very small offset. Beyond 10 Rs, near the noon meridian, the field topology is characteristic of a dipole field being compressed by high‐speed solar wind. There is no evidence of plasma outflow, i.e., a planetary wind. Near the dawn meridian the field lines in the outer magnetosphere are stretched‐out into a nearly equatorial orientation. Crossings of a thin current sheet are observed, apparently caused by motions driven from outside the magnetosphere. The field above and below the current sheet spirals out of the magnetic meridian plane at large distances to point tailward and parallel to the magnetopause. The location of the magnetopause is consistent with a shape that is similar to that of the earth but perhaps more blunt, as suggested by the attitude of the magnetopause near dawn. Near both the noon and dawn magnetopause the field in the magnetosheath equals or exceeds the field in the magnetosphere. The noon observations suggest a piling‐up of magnetosheath field lines adjacent to the magnetopause. Large impulsive field compressions are observed in the magnetosheath near noon. Multiple crossings of the bow shock are observed, and the absence of significant changes in field direction shows that it is quasi‐perpendicular. The speeds of motion of the shock toward and away from Saturn are estimated to be 150 and 50 km/s, respectively. A shock thickness of ∼2000 km is inferred.