Origin and Evolution of the Multi-band Variability in the Flat Spectrum
  Radio Source 4C 38.41
  The flat spectrum radio quasar 4C 38.41 showed a significant increase of its
radio flux density during the period 2012 March - 2015 August which correlates
with gamma-ray flaring activity. Multi-frequency simultaneous VLBI observations
were conducted as part of the interferometric monitoring of gamma-ray bright
active galactic nuclei (iMOGABA) program and supplemented with additional
monitoring observations at various bands across the electromagnetic spectrum.
The epochs of the maxima for the two largest gamma-ray flares coincide with the
ejection of two respective new VLBI components and the evolution of the
physical properties seem to be in agreement with the shock-in-jet model.
Derived synchrotron self absorption magnetic fields, of the order of 0.1 mG, do
not seem to dramatically change during the flares, and are much smaller, by a
factor 10,000, than the estimated equipartition magnetic fields, indicating
that the source of the flare may be associated with a particle dominated
emitting region.
