Polarization flare of 3C 454.3 at millimeter wavelengths seen from decadal polarimetric observations

Context. The blazar 3C 454.3 ( z = 0.859) has been extensively investigated using multiwavelength high-resolution polarization studies, showing polarization variations on milliarcsecond scales. Aims. This study investigates the polarimetric characteristics of the blazar 3C 454.3 at 22–129 GHz using decadal (2011–2022) data sets. In addition, we also delve into the origin of the polarization flare observed in 2019. Methods. The corresponding data sets were obtained from the single-dish mode observations of the Korean VLBI Network (KVN) and the 43 GHz Very Long Baseline Array (VLBA). Using those data, we compared the consistency of the measurements between milliarcsecond and arcsecond scales. The Faraday rotation measure (RM) values were obtained via two approaches: model fitting to a linear function in all frequency ranges and calculating from adjacent frequency pairs. Results. We found that the preferred linear polarization angle is ∼100° when the source is highly polarized, for example during a flare. At 43 GHz we found that the polarized emission at of milliarcsecond and arcsecond scales is consistent when we compare its flux density and polarization angle. The ratio of quasi-simultaneously measured (within a week) polarized flux density is 1.02 ± 0.07 (i.e., Δ S p / S p ≈ 2%) and the polarization angles display similar rotation, which suggest that the extended jet beyond the scale of VLBA 43 GHz has a negligible convolution effect on the polarization angle from the KVN. We found an interesting and notable flaring event in the KVN single-dish data from the polarized emission in 2019 in the frequency range of 22–129 GHz. During the flare, the observed polarization angles ( χ obs ) rotate from ∼150° to ∼100° at all frequencies with a chromatic polarization degree ( m p ). Conclusions. Based on the observed m p and χ obs , and also on the Faraday rotation measure, we suggest that the polarization flare in 2019 is attributed to the shock–shock interaction in the stationary jet region. The change in the viewing angle of the jet alone is insufficient to describe the increase in brightness temperature, indicating the presence of source intrinsic processes such as particle acceleration.