Title: The physics of AGN jets revealed by full-Stokes monitoring at mm and cm wavelengths Author list: Ioannis Myserlis, Ivan Agudo, Clemens Thum, Ramprasad Rao, Daniel Homan, Svetlana Jorstad, Alan Marscher, Alex Kraus, Emmanouil Angelakis Abstract: Jets of Active Galactic Nuclei (AGN) comprise the most energetic, long-term phenomenon in the Universe. They emerge from the vicinity of Super Massive Black Holes (SMBHs) and propagate with relativistic velocities, as high as 0.9998c, to distances much greater than their host galaxies, even > 1 Mpc. In the case of blazars, these jets are closely aligned to our line of sight (< 5º), which results in extreme boosting of their emission, making them ideal targets to study the jet physics in detail. Magnetic fields are thought to play a key role in the jet production, acceleration and collimation and they are also responsible for the observed linear and circular polarization. In addition, blazars exhibit flaring events across the electromagnetic spectrum with timescales ranging from months down to minutes. The mechanisms that have been proposed to explain this variability, e.g. relativistic shocks or magnetic reconnection, predict distinct polarization variability characteristics. Therefore, dense monitoring of the linear and circular polarization emission from AGN jets is a powerful tool to disentangle these processes and study the physical conditions in AGN jets. Here I will give an overview of blazar variability at mm and cm wavelengths, both in total flux and polarization, as revealed by dedicated, long-term, high-cadence monitoring programs running at several large radio facilities around the globe. I will discuss the challenges involved to achieve robust calibration and deliver high-precision, multi-frequency, full-Stokes radio data trains and showcase the jet physical conditions and variability mechanism characteristics that can be constrained using them. Finally, I will present selected examples of time domain studies of AGN jets and demonstrate how they are augmented by the combined analyses using high angular resolution radio images and concurrent observations in other bands.

Poster presented at the conference "XVI Reunión Científica de la SEA", held in Granada (Spain) in July 2024, at the "Galaxias" parallel session.