THE IO-C JOVIAN DECAMETER EMISSIONS

We report on the analysis of Io-C sources observed at Nancay observato ry (France). The study of Io-C morphology, from the dynamic spectra, a llows us to show the recurrence of fine emission features in the same region of the CML-Io diagram. Thus the component, with right-hand pola rization, has a constant spectrum, one large vertex-late are reaching frequencies of about 30 MHz. Simultaneously, the structures with left- hand polarization, observed at frequencies less than 25 MHz, present t wo samples: splitting and vertex-late arcs. We find a temporal correla tion between the right-hand and left-hand polarization structures, whe re the splitting seems to be the precursor of the rest of the emission . The analysis of Io-C dynamic spectra is completed by the measurement s of the Stokes polarization parameters. In this case we show that the polarization for a given event is the same for the splitting and vert ex-late arcs, where both have left-hand polarizations. To interpret ou r results we compare our spectral observations to the Goldstein-Thiema n model. We show correspondence between model and observation concerni ng the arc structures. But there is no correspondence when we take in consideration both polarizations and we try to explain the common spec tral and temporal features. This correlation between both components s eems to be more evident if they are associated to one and the same emi ssion cone located in one hemisphere.