  Synchrotron radiation is commonly observed in connection with shocks of
different velocities, ranging from relativistic shocks associated with active
galactic nuclei, gamma-ray bursts or microquasars to weakly- or
non-relativistic flows as those observed in supernova remnants. Recent
observations of synchrotron emission in protostellar jets are important not
only because they extend the range over which the acceleration process works,
but also because they allow to determine the jet and/or interstellar magnetic
field structure, thus giving insights on the jet ejection and collimation
mechanisms. In this paper, we compute for the first time polarized
(synchrotron) and non polarized (thermal X-ray) synthetic emission maps from
axisymmetrical simulations of magnetized protostellar jets. We consider models
with different jet velocities and variability, as well as toroidal or helical
magnetic field. Our simulations show that variable, low-density jets with
velocities $\sim$ 1000 km s$^{-1}$ and $\sim$ 10 times lighter than the
environment can produce internal knots with significant synchrotron emission,
and thermal X-rays in the shocked region of the leading bow shock moving in a
dense medium. While models with a purely toroidal magnetic field show a very
large degree of polarization, models with helical magnetic field show lower
values and a decrease of the degree of polarization, in agreement with
observations of protostellar jets.
