Remote sensing of the Io torus plasma ribbon using  natural radio occultation of the Jovian radio emissions

Abstract. We study the Jovian hectometric (HOM) emissions recorded by the RPWS (Radio and Plasma Wave Science) experiment onboard the Cassini spacecraft during its Jupiter flyby. We analyze the attenuation band associated with the intensity extinction of HOM radiation. This phenomenon is interpreted as a refraction effect of the Jovian hectometric emission inside the Io plasma torus. This attenuation band was regularly observed during periods of more than 5 months, from the beginning of October 2000 to the end of March 2001. We estimate for this period the variation of the electron density versus the central meridian longitude (CML). We find a clear local time dependence. Hence the electron density was not higher than 5.0 × 104 cm−3 during 2 months, when the spacecraft approached the planet on the dayside. In the late afternoon and evening sectors, the electron density increases to 1.5 × 105 cm−3 and reach a higher value at some specific occasions. Additionally, we show that ultraviolet and hectometric wavelength observations have common features related to the morphology of the Io plasma torus. The maxima of enhancements/attenuations of UV/HOM observations occur close to the longitudes of the tip of the magnetic dipole in the southern hemisphere (20° CML) and in the northern hemisphere (200° CML), respectively. This is a significant indication about the importance of the Jovian magnetic field as a physical parameter in the coupling process between Jupiter and the Io satellite.

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Electromagnetic interaction between Jupiter's ionosphere and the Io plasma torus

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309030610 ◽

2008 ◽

Vol 4 (S259) ◽

pp. 271-282 ◽

Cited By ~ 1

Author(s):

Yi-Jiun Su

Keyword(s):

Electric Fields ◽

Electromagnetic Interaction ◽

Static System ◽

Radio Emissions ◽

Coupling System ◽

Plasma Torus ◽

Set Up ◽

Io Plasma Torus ◽

Electromagnetic Disturbances ◽

Coupling Mechanisms

AbstractThe electromagnetic interaction between Jupiter and Io has been studied extensively since the discovery of Io-controlled decametric radio emissions (DAMs). A variety of mechanisms for electromagnetic disturbances have been considered including a unipolar inductor, the excitation of large-amplitude Alfvén waves, the generation of electrostatic electric fields parallel to the ambient magnetic field, and etc. Recently, three auroral acceleration regions categorized by terrestrial physicists have been applied to the Jupiter-Io coupling system: the Alfvénic acceleration region is associated with bright emissions at Io's magnetic footprint, whereas the quasi-static system of anti-planetward and planetward currents set up at the inner and outer edges of the torus in the downstream region of Io's wake. This review paper summarizes the current understanding of the coupling mechanisms between Jupiter's ionosphere and the Io plasma torus, as well as the electron acceleration mechanism necessary to excite Io-associated emissions.

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Modelling the electron density distribution in the Io Plasma Torus using Juno radio occultations

10.5194/egusphere-egu2020-13221 ◽

2020 ◽

Author(s):

Marco Zannoni ◽

Alessandro Moirano ◽

Luis Gomez Casajus ◽

Paolo Tortora ◽

Daniele Durante ◽

...

Keyword(s):

Electron Density ◽

Temporal Variations ◽

Parametric Models ◽

High Electron ◽

Path Delay ◽

Radio Science ◽

Ground Station ◽

Plasma Torus ◽

Almost All ◽

Io Plasma Torus

The innermost galileian moon Io hosts an intense volcanic activity, which ejects about 103 kg/s of gas into Jupiter's magnetosphere. Here these neutrals are ionized by interaction with the background plasma and they are accelerated from keplerian velocity to corotation velocity thanks to Alfv&#233;n's theorem. This plasma cloud around the planet (the so-called Io Plasma Torus or IPT) slowly diffuses across Jupiter's magnetic field, but high electron densities (>1000-2000 cm-3) are found between 5-8 RJ.Juno is travelling along highly eccentric, polar orbits around the planet and flies very close to Jupiter's surface during each perijove. Thus, the radio links used for ground communication and radio science cross the IPT both in the uplink and the downlink leg. Being a dispersive medium, the torus introduces a different path delay on the X/X and Ka/Ka links established between the Ground Station and the spacecraft. Thus, the path delay can be extracted through a linear combination of the two links, and then quantitatively analyzed and fitted to different parametric models of the IPT.In this work we have used almost all the available Juno radio occultations of the IPT in order to improve an already existing model by introducing both longitudinal and temporal variations of the electron density. To this end, we looked for the 2D Fourier expansion in longitude and time of the parameters of this model with the goal of minimizing the residuals of the fit and pointing out periodicities in the morphology of the torus.

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