ASYMMETRY OF JETS, LOBE LENGTH AND SPECTRAL INDEX IN QUASARS

The less depolarized lobe of a radio source is generally the lobe cont aining the jet (Laing-Garrington correlation) but the less depolarized lobe is also generally that with the flatter radio spectrum (Liu-Pool ey correlation), Both effects are strong; taken together they would im ply a correlation between jet side and lobe spectral index, i.e. betwe en an orientation-dependent feature and one that is intrinsic. We test this prediction using detailed spectral imaging of a sample of quasar s with well-defined jets and investigate whether the result can be rec onciled with the standard interpretation of one-sided jets in terms of relativistic aberration, Our central finding is that the spectrum of high surface brightness regions is indeed flatter on the jet side, but that the spectrum of low surface brightness regions is flatter on the side with the longer lobe, We discuss possible causes for these corre lations and favour explanations in terms of relativistic bulk motion i n the high surface,brightness regions and differential synchrotron age ing in the extended lobe material.