Extragalactic jets as current-carrying systems. III - Energy requirements and critical discussion

Abstract In this paper the equilibrium model developed in the first paper of this series, by Chiuderi, Pictrini, and Torricelli-Ciamponi, to describe extragalactic jets is critically reviewed. In particular, two aspects have been analyzed and compared with the observational constraints: the global energy flux convected by the cylindrical jet and the ranges of the equilibrium parameters allowed by the stability analysis. As far as the second topic is concerned, much attention has been devoted to convert the results obtained from the temporal stability analysis into a spatial point of view. In conclusion it turns out that the model is well suited to describe class I, low-power jets even if, in some cases, there are indications that the model should be improved by taking into account a longitudinal dependence of the equilibrium parameters.