  Using the relativistic MHD code MPI-AMRVAC and a radiative transfer code in
post-processing, we explore the influence of the magnetic-field configuration
and transverse stratification of an over-pressured jet on its morphology, on
the moving shock dynamics, and on the emitted radio light curve. First, we
investigate different large-scale magnetic fields with their effects on the
standing shocks and on the stratified jet morphology. Secondly, we study the
interaction of a moving shock wave with the standing shocks. We calculate the
synthetic synchrotron maps and radio light curves and analyse the variability
at two frequencies 1 and 15.3 GHz and for several observation angles. Finally,
we compare the characteristics of our simulated light curves with radio flares
observed from the blazar 3C 273 with OVRO and VLBA in the MOJAVE survey between
2008 and 2019. We find that, in a structured, over-pressured relativistic jet,
the presence of the large-scale magnetic field structure changes the properties
of the standing shock waves and leads to an opening of the jet. When crossing
such standing shocks, moving shock waves accompanying overdensities injected in
the base of the jet are causing very luminous radio flares. The observation of
the temporal structure of these flares under different viewing angles probes
the jet at different optical depths. At 1 GHz and for small angles, the
self-absorption caused by the moving shock wave becomes more important and
leads to a drop in the observed flux after it interacts with the brightest
standing knot. A weak asymmetry is seen in the shape of the simulated flares,
resulting from the remnant emission of the shocked standing shocks. The
characteristics of the simulated flares and the correlation of peaks in the
light curve with the crossing of moving and standing shocks favor this scenario
as an explanation of the observed radio flares of 3C 273.
