The analysis of selected Jovian narrow-band emission events allows us to study their characteristics and in particular the relationship with the Riihimaa structures (Riihimaa 1991). It is shown that the temporal modulation of the narrow-band involves the presence of fine structures, i.e. S-bursts, which seem to be the residue of the narrow-band. In this framework, a complete structure, e.g. type r , can be decomposed in three parts, each one depending on the way the narrow-band is perturbated. The short time scale of the gaps in the band (about few tens of milliseconds) and the individual S-burst duration (about few hundred of milliseconds) account for a mechanism which seems to be totally intrinsic to the source. Taking into consideration our findings, we discuss and compare them to three models with the aim to give some explication of the narrow-band origin. It appears that the classic model (i.e. Ellis model) cannot explain the relation between the narrow-band and the inherent fine structures. The two other models, the feedback model (Calvert 1982) and the filamentary model (Louarn 1997), seem to account for a great number of observed features. Although both models can be adapted to explain part of the observed feature but not the global observed phenomena.
According to our analysis a realistic model for S-bursts should first take into account inherent effects (e.g. refraction effects, oscillations of the emitting wave plane...) inside, or close, to the source region which generates the narrow-band emissions. Then the model must allow a temporal fragmentation of this band involving the appearance of fine structures which will be a residue of the narrow-band after its disappearance.
© European Southern Observatory (ESO) 2000
Online publication: December 5, 2000