1995A&A...293..626V

In the framework of the analytical study of helically symmetric magnetohydrodynamic (MHD) equilibria with non-uniform density, exact solutions of the set of time-independent MHD equations completed by a non-barotropic equation of state are considered in order to construct models for the interpretation of the helical morphology of some astrophysical jets. General models are obtained by imposing some physically relevant constraints on the equilibrium solutions, and their basic characteristics are analyzed in typical examples of superalfvenic flows. Moreover, specific models for the description of the main features of the M 87 jet are presented in both the superalfvenic and subalfvenic cases: the latter seems to be more suitable to describe the abrupt structural transition exhibited by the jet, and the distribution of emission which comes out from the model matches well with the highest quality observations.