Radio-frequency spectra and jets from astrophysical systems: plasma features of their sources

We discuss the most important astrophysical radio-sources, like Radio-Galaxies and Quasars, Pulsar Radio-Jets and Supernova Remnants. The fundamental features of the radio-emission of these sources are presented and the basic mechanisms at the ground of their morphology are developed in some details, especially in view of the role played by the plasma configurations surrounding compact sources. The fundamental link between the morphology of the astrophysical radio-sources and the plasma configurations surrounding the compact objects is outlined to be the accretion process, whose profile significantly affects the synchrotron emission of the source. The fundamental ideas concerning the angular momentum transport across accretion disks are discussed, by stressing their successes and their shortcomings. An alternative scenario, based on a close parallelism with the laboratory plasma configurations, is then inferred. We will focus our attention on the morphology of the radio-jets and on the possible triggering phenomena, viewed as profiles of plasma instabilities.