Jovian radio wave propagation through the Io plasma torus

International audienceWe report on the Jovian radio wave propagationthrough the Io torus plasma. We select cases ofJovian hectometric (HOM) emission which aresubject to attenuation effect. The morphology ofsuch phenomena is characterized by the use ofRPWS experiment observations recorded duringthe Cassini Jupiter flyby. This attenuation isshown to depend on the Jovian magnetic fieldwhere clear modulations appear at two centralmeridian longitudes around ~180° and ~50°,corresponding respectively to the position of themagnetic field axis in the Northern and Southernhemispheres. A detailed analysis of the dynamicspectra leads us to confirm (previous work byLecacheux, JGR, 85, 1980) the presence ofrefraction effect caused by the Io plasma torus.The Jovian radio wave presents different spectralfeatures when it propagates through the Io plasmatorus. We note in particular three main cases: atotal emission extinction, a partial decrease of theradiation and an enhancement of the intensitybefore and after the attenuation of HOM emission.The origins of such spectral effects depend on: thesource location (in the Northern or Southernhemisphere), the observer position (e.g. Cassinispacecraft) with regard to the magnetic equator ofthe planet, and the electronic density in the Iotorus. We discuss our results and compare them toprevious studies based on data recorded byVoyager, Galileo and Cassini spacecraf