Abstract

We report on the Jovian hectometric (HOM) emissions recorded by the RPWS (Radio and Plasma Wave Science) experiment onboard the Cassini spacecraft during its Jupiter flyby. The capabilities of the RPWS experiment enable us to analyze the intensity extinction of HOM radiation, the so-called attenuation band. This phenomenon is interpreted as a refraction effect of the HOM emission inside the Io plasma torus. We estimate the variation of the electron density versus the central meridian longitude (CML). The intensity extinction at frequencies higher than 3 MHz and up to 5 MHz implies the presence of particular electronic density irregularities in the Io torus. Volcanic activity, particularly in the northern hemisphere of the Io satellite, may be the source of such Io torus plasma irregularities.