  Chromospheric jets are plausible agents of energy and mass transport in the
solar chromosphere, although their driving mechanisms have not yet been
elucidated. Magnetic field measurements are key for distinguishing the driving
mechanisms of chromospheric jets. We performed a full Stokes synthesis in the
infrared range with a realistic radiative magnetohydrodynamics simulation that
generated a chromospheric jet to predict spectro-polarimetric observations from
the Sunrise Chromospheric Infrared spectro-Polarimeter (SCIP) onboard the
SUNRISE III balloon telescope. The jet was launched by the collision between
the transition region and an upflow driven by the ascending motion of the
twisted magnetic field at the envelope of the flux tube. This motion is
consistent with upwardly propagating non-linear Alfvenic waves. The upflow
could be detected as continuous Doppler signals in the CaII 849.8 nm line at
the envelope where the dark line core intensity and strong linear polarisation
coexist. The axis of the flux tube was bright in both FeI 846.8 nm and CaII
849.8 nm lines with down-flowing plasma inside it. The structure, time
evolution, and Stokes signals predicted in our study will improve the physical
interpretation of future spectro-polarimetric observations with SUNRISE
III/SCIP.
