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

Abstract

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 × 10 4 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 × 10 5 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.

On the ultraviolet anomalies of the WASP-12 and HD 189733 systems: Trojan satellites as a plasma source

“…These materials form extended clouds along Io's orbit, and over time are ionized by two main processes: electron impact and charge exchange reactions. The ionized components are rapidly accelerated under the effect of the Jovian magnetic field and form a ring-like structure known as Io plasma torus, where electron density reaches 10 4 cm −3 (Boudjada et al 2014). To supply the electron densities observed in the plasma torus, Io ejects mainly S + and O + ions at rates of ≈2×10 28 s −1 (Thomas et al 2004).…”