Galileo radio occultation measurements of Io's ionosphere and plasma wake

Hinson, D. P.; Kliore, A. J.; Flasar, F. M.; Twicken, Joseph D.; Schinder, P. J.; Herrera, R. G.

doi:10.1029/98ja02659

Cited by 65 publications

(53 citation statements)

References 28 publications

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“…The maximum electron densities measured during each of the four flybys are summarized in Table 1, along with the type of flyby, the altitude at closest approach, the local time at closest approach, and the solar zenith angle at closest approach. Since Io is known from radio occultation measurements to have an ionosphere [Ktiore et at., 1974[Ktiore et at., , 1975Hinson et at., 1998], the question naturally arises whether the density enhancements observed are due to Io's ionosphere. For a gravitationally bound ionosphere the electron density is expected to have approximate spherical symmetry and to decrease exponentially with increasing height, with a scale height given by H = kT/mg.…”

Section: Discussionmentioning

confidence: 99%

Electron densities near Io from Galileo plasma wave observations

Gurnett¹,

Persoon²,

Kŭrth³

et al. 2001

J. Geophys. Res.

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Abstract. This paper presents an overview of electron densities obtained near Io from the Galileo plasma wave instrument during the first four flybys of Io. These flybys were I0, which was a downstream wake pass that occurred on December 7, 1995; 124, which was an upstream pass that occurred on October 11, 1999; 125, which was a south polar pass that occurred on November 26, 1999; and 127, which was an upstream pass that occurred on February 22, 2000. Two methods were used to measure the electron density. The first was based on the frequency of upper hybrid resonance emissions, and the second was based on the low-frequency cutoff of electromagnetic radiation at the electron plasma frequency.

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Section: Discussionmentioning

confidence: 99%

Electron densities near Io from Galileo plasma wave observations

Gurnett¹,

Persoon²,

Kŭrth³

et al. 2001

J. Geophys. Res.

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“…"Galileo" discovered beams of fast electrons with an energy greater than 15 keV on force lines of the magnetic field passing through Io. The beams propagated in two directions along the magnetic field and had approximately equal intensity (Frank et al 1996;Kivelson et al 1996;Williams et al 1996;Bagenal 1997;Hinson et al 1998). The problem, how the induced electric field (1), applied to satellite Io, manifests itself in the form of accelerated electrons moving along the magnetic field, has been studied in a number of papers.…”

Section: Electron Accelerationmentioning

confidence: 99%

Dependence of the Io-related decametric radio emission of Jupiter on the central meridian longitude and Io's “active” longitudes

Зайцев

Шапошников

Rücker

2006

A&A

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Context. The statistical analysis of the Io-related decametric radio emission of Jupiter shows that this emission depends precisely on the central meridian longitude. This dependence is the result of the existence of Io's "active" longitudes, i.e. particular regions of Io's orbit, which are fixed with respect to the Jovian magnetic field and at which Io-related emission occurs more often. Aims. The paper considers the mechanism of the formation of Io's "active" longitudes. Methods. The formation of Io's "active" longitudes is caused by two factors: first, the change of the efficiency of particle acceleration in Io's ionosphere, depending on Io's longitude, and second, the degree of broadening of the angular spectrum of accelerated electrons during their passing through the plasma torus. Results. It is shown that the mechanism considered explains rather well why Io-related decametric bursts begin to appear much more often in longitudes of the range 120• < ∼ λ Io < ∼ 300• (λ Io is the longitude in the frame III), and why one predominantly observes the emission from the sources located in the northern Jovian hemisphere.

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“…This improvement in SNR will allow accurate sounding at finer vertical resolution than reported here. These high-resolution profiles will be obtained through use of a retrieval algorithm that accounts for diffraction effects, which was developed recently by Karayel and Hinson [1997] and has been applied successfully to radio occultation soundings of the ionospheres of Jupiter [Hinson et al, 1998a] and Io [Hinson et al, 1998b]. …”

Section: Departures From Spherical Symmetrymentioning

confidence: 99%

Initial results from radio occultation measurements with Mars Global Surveyor

Hinson¹,

Simpson²,

Twicken³

et al. 1999

J. Geophys. Res.

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272

238

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Abstract.A series of radio occultation experiments conducted with Mars Global Surveyor in early 1998 has yielded 88 vertical profiles of the neutral atmosphere. The measurements cover latitudes of 29øN to 64øS and local times from 0600 through midnight to 1800 during early summer in the southern hemisphere (Ls -264 ø-308 ø). Retrieved profiles of pressure and temperature versus radius and geopotential extend from the surface to the 10-Pa pressure level. Near-surface uncertainties in temperature and pressure are about i K and 2 Pa, respectively, far smaller than in previous radio occultation measurements at Mars. The profiles resolve the radiativeconvective boundary layer adjacent to the surface and also reveal gravity waves, particularly at northern and equatorial latitudes, which appear to be breaking in some cases. Distinctive meridional gradients of pressure and temperature indicate the presence of a low-altitude westerly jet at latitudes of 15ø-30øS at southern summer solstice. This jet appears in predictions of general circulation models in connection with the strong, seasonal, cross-equatorial Hadley circulation. The pressure gradient at •02 km altitude implies a wind speed of 33 m s -t, stronger than predicted, which may help explain the occurrence of numerous local dust storms within this latitude band in late southern spring. These measurements also characterize the response of the atmosphere to stationary thermal forcing at midsouthern latitudes, where high terrain south of Tharsis and low terrain in Hellas Planitia produce large, zonal temperature variations in the lowest scale height above the surface. Pressure measured at constant geopotential decreases at an average rate of 0.13% per degree Ls, due primarily to condensation of CO2 at the North Pole.

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Galileo radio occultation measurements of Io's ionosphere and plasma wake

Cited by 65 publications

References 28 publications

Electron densities near Io from Galileo plasma wave observations

Electron densities near Io from Galileo plasma wave observations

Dependence of the Io-related decametric radio emission of Jupiter on the central meridian longitude and Io's “active” longitudes

Initial results from radio occultation measurements with Mars Global Surveyor

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