SIMBAD references

Inhomogeneities can influence the polarization emerging from a synchrotron source. However, it is shown that the frequency distribution of circular polarization is only marginally affected, although its magnitude may change substantially. This is used to argue that the observed properties of compact radio sources imply a radiating plasma in which the characteristic waves are nearly circular. As a result, restrictions can be put on the low-energy part of the energy distribution of the relativistic electrons as well as the presence of electron-positron pairs. It is emphasized that this constrains theoretical modeling of the acceleration process for the relativistic electrons; for example, some of the currently popular scenarios seem to need modifications to become consistent with observations.