Simulating the dynamics and synchrotron emission from relativistic jets
  II. Evolution of non-thermal electrons
  We have simulated the evolution of non-thermal cosmic ray electrons (CREs) in
3D relativistic magneto hydrodynamic (MHD) jets evolved up to a height of 9
kpc. The CREs have been evolved in space and in energy concurrently with the
relativistic jet fluid, duly accounting for radiative losses and acceleration
at shocks. We show that jets stable to MHD instabilities show expected trends
of regular flow of CREs in the jet spine and acceleration at a hotspot followed
by a settling backflow. However, unstable jets create complex shock structures
at the jet-head (kink instability), the jet spine-cocoon interface and the
cocoon itself (Kelvin-Helmholtz modes). CREs after exiting jet-head undergo
further shock crossings in such scenarios and are re-accelerated in the cocoon.
CREs with different trajectories in turbulent cocoons have different
evolutionary history with different spectral parameters. Thus at the same
spatial location, there is mixing of different CRE populations, resulting in a
complex total CRE spectrum when averaged over a given area. Cocoons of unstable
jets can have an excess build up of energetic electrons due to re-acceleration
at turbulence driven shocks and slowed expansion of the decelerated jet. This
will add to the non-thermal energy budget of the cocoon.
