Outburst in the polarized structure of the compact jet of 3C 454.3

We present three-epoch polarimetric images of the quasar 3C 454.3 obtained with the Very Long Baseline Array at 22 and 43 GHz. Polarized intensity ima ges at 22 GHz show a sudden change in the polarization structure of a brigh t eastern component (which we call the "core," although it may be neither a t the upstream end of the jet nor completely stationary) over a 41 day inte rval, coincident with the ejection of a new component from the core, as res olved in the corresponding 43 GHz images. This polarization outburst is als o present at 43 GHz in both the core and the new component. This may repres ent a rapid change in the electric vector position angle of the ejected com ponent from being orthogonal to that of the core to being almost parallel t o it. About 7 months later, the new component, moving superluminally at 2.9 +/- 0.4 h(-1) c (q(0) = 0.5) relative to the core and 3.9 +/- 0.4 h(-1) c relative to a bright stationary component about 0.6 mas west of the core-ve ry low compared with previous measurements-is found at 43 GHz to exhibit a further rotation of 90 degrees in the orientation of its polarization. Opac ity effects may account for the first rotation, but changes in the magnetic field of the component and/or that of the underlying jet in the inner mill iarcsecond structure of 3C 454.3 are needed to account for the second. Pola rized intensity images of the quasar 0420-014, used as a calibrator, are al so presented. The polarization position angle of the core rotated between l ate 1994 and late 1996.