The atmosphere of Io from Pioneer 10 radio occultation measurements

Kliore, A. J.; Fjeldbo, G.; Seidel, B. L.; Sweetnam, D. N.; Sesplaukis, T. T.; Woiceshyn, P. M.; Rasool, S. I.

doi:10.1016/0019-1035(75)90057-3

Cited by 115 publications

(48 citation statements)

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“…Such a density is consistent with the HST observations, as is the reduced density observed on Ganymede. The ionosphere of Io was discovered by the radio occultation of Pioneer 10 ( Kliore et al, 1975), and it and its underlying atmosphere have been the subject of numerous studies and observations since then (Johnson and Matson 1976;Kumar andHunten 1982, Kumar 1985;Lellouch et al, 1990Lellouch et al, , 1992. The atmosphere of Io is fundamentally different from those of the icy Galilean satellites, consisting of SO2 ejected from volcanoes and possibly sulphur and its compounds sputtered from its surface.…”

Section: 000mentioning

confidence: 99%

“…Interpretation of the effects of refraction by the planetary ionosphere and atmosphere allows one to infer the electron density structure in the ionosphere and the temperature-pressure profiles and absorption characteristics of the neutral atmosphere (Kliore 1972b, Fjeldbo et al, 1971.…”

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confidence: 99%

“…This technique has been used very successfully to measure the characteristics of the ionospheres and atmospheres of Venus (Kliore et al, 1967;Fjeldbo et al, 1971;Kliore and Patel 1980); Mars (Kliore et al, 1965;Kliore et al, 1972a;Lindal et al, 1979); Mercury (Howard et al, 1974); Jupiter (Fjeldbo et al, 1975;Eshleman et al, 1979;Lindal et al, 1981;Hinson et al, 1997); Saturn Tyler et al, 1981;Lindal et al, 1985); Uranus (Lindal et al, 1987); Neptune (Tyler et al, 1989;Lindal 1992); Saturn's rings (Marouf and Tyler 1985); as well as Saturn's satellite Titan (Lindal et al, 1983); Neptune's Triton (Tyler et al, 1989); and Jupiter's satellites Io (Kliore et al, 1975) and Europa (Kliore et al, 1997).…”

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confidence: 99%

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Satellite Atmospheres and Magnetospheres

Kliore

1998

Highlights astron.

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Satellite Atmospheres and Magnetospheres

Kliore

1998

Highlights astron.

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“…Spacecraft exploration of the Jovian environment and of the magnetic shells in Io's vicinity in particular identified further important features of Io's interaction with the surrounding plasma. Radio occultation measurements by Pioneer 10 revealed that Io had an ionosphere [Kliore et al, 1975]. Webster et al [1969] first suggested any currents carried by Io are likely to close through such a highly conducting region rather than through the solid part of the satellite.…”

Section: Introductionmentioning

confidence: 99%

Io and its plasma environment

Southwood¹,

Kivelson²,

Walker³

et al. 1980

J. Geophys. Res.

124

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We describe and examine the interaction of Io with its plasma torus and the Jovian magnetic field in the context of several currently popular models. We address three specific matters. First, we discuss features implied by sub-Alfvenic flow which must be common to all models. Next, we examine the magnetic signature observed near Io by the Goddard Space Flight Center Voyager I magnetometer and point out that the preliminary estimate of 5 x 106 A current may be an overestimate. We obtain good fits with alternative current distributions which yield currents as small as 7 x 105 A through Io. The best fits are obtained for an Alfven Mach number (MA) of 0.15, but good fits are also found for 0.1 < MA < 0.25. Lastly, we point out the crucial role of charged particle data for probing the near Io interaction. We use published data from the low energy charged particle (LECP) detector to suggest that Io has an intrinsic magnetic field of magnitude comparable with earlier estimates. We make predictions which can test this picture as further data become available.

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“…Hubbard et al [1975], Eshleman [1975], and Eshleman and Tyler [1975] were the first to appreciate the problem and to provide an understanding of the characteristic shape of the error profiles. Kliore and Woiceshyn [1976] provided a procedure for treating data from an oblate planet. Recently, Syndergaard [1998] has provided estimates of temperature errors resulting from neglect of Earth's oblateness.…”

Section: Introductionmentioning

confidence: 99%

Systematic errors in atmospheric profiles obtained from Abelian inversion of radio occultation data: Effects of large‐scale horizontal gradients

Ahmad¹,

Tyler²

1999

J. Geophys. Res.

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Abstract. Reduction of radio occultation data to retrieve atmospheric profiles (T-p(r)) requires knowledge or assumption of the horizontal structure of the atmosphere. In the case of terrestrial planets the atmosphere in the vicinity of ray periapsides usually is assumed to be spherically symmetric. This assumption leads to an integral transform relationship between the profiles of refractivity versus radius and the total bending angle versus the asymptotic closest approach of rays, where the latter is directly obtainable from occultation frequency data and trajectory information. Occultation studies of the giant planets have demonstrated that departures from spherical symmetry, if not accounted for, can result in serious errors in derived T-p(r) profiles. We analyze errors in atmospheric profiles due to large-scale departures from spherical symmetry. For analytic convenience we represent departures from spherical symmetry as locally spherical structures with center of curvature offset in three dimensions from the center of mass, from which follow analytic expressions for errors in bending angle and impact parameter as functions of the offset and trajectory parameters. Since these expressions are not restricted to any specific occultation type, it is easy to identify the geometrical configurations and the specific trajectory parameters that enhance or suppress these errors. Errors in bending angle and impact parameter carry over into the refractivity and radius profiles, while at the same time, new errors are introduced because the bending angle versus impact parameter profile is integrated along a nonvertical path in the presence of large-scale departures from spherical symmetry, to obtain refractivity and radius profiles. Similarly, refractivity and radius errors propagate into the temperature and pressure profiles, while a nonvertical path of integration in the presence of horizontal gradients provides another opportunity for new errors to be introduced. We estimate that fractional errors in temperature profiles can be as large as a few percent for the Martian atmosphere above 20 km, decreasing in magnitude closer to the surface. For Earth, such errors are estimated to be less than 1% above 30 km. In the lower parts of Earth's atmosphere, however, and especially in the lower troposphere, these errors can be very sensitive to horizontal gradients and hence highly variable; typically, the error magnitude remains less than 2% for the dry regions of Earth's troposphere. We have not addressed the effect on errors of water vapor gradients, or of more extreme structures such as sharp weather fronts. A small variation on this approach can incorporate errors due to imprecise knowledge of the transmitter and receiver trajectories. IntroductionRadio occultation is a remote sensing method for "sounding" planetary atmospheres. Since its inception in the early 1960s, this methodology has been used to obtain high vertical resolution profiles of atmospheric temperature and pressure for most of the planets of the solar system...

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The atmosphere of Io from Pioneer 10 radio occultation measurements

Cited by 115 publications

References 10 publications

Satellite Atmospheres and Magnetospheres

Satellite Atmospheres and Magnetospheres

Io and its plasma environment

Systematic errors in atmospheric profiles obtained from Abelian inversion of radio occultation data: Effects of large‐scale horizontal gradients

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