  We study the polarization signals and physical parameters of penumbral
microjets (PMJs) by using high spatial resolution data taken in the Fe I 630 nm
pair, Ca II 854.2 nm and Ca II K lines with the CRISP and CHROMIS instruments
at the Swedish 1-m Solar Telescope. We infer their physical parameters, such as
physical observables in the photosphere and chromospheric velocity diagnostics,
by different methods, including inversions of the observed Stokes profiles with
the STiC code. PMJs harbor overall brighter Ca II K line profiles and
conspicuous polarization signals in Ca II 854.2 nm, specifically in circular
polarization that often shows multiple lobes mainly due to the shape of Stokes
I. They usually overlap photospheric regions with sheared magnetic field
configuration, suggesting that magnetic reconnections could play an important
role in the origin of PMJs. The discrepancy between their low LOS velocities
and the high apparent speeds reported on earlier, as well as the existence of
different vertical velocity gradients in the chromosphere, indicate that PMJs
might not be entirely related to mass motions. Instead, PMJs could be due to
perturbation fronts induced by magnetic reconnections occurring in the deep
photosphere that propagate through the chromosphere. This reconnection may be
associated with current heating that produces temperature enhancements from the
temperature minimum region. Furthermore, enhanced collisions with electrons
could also increase the coupling to the local conditions at higher layers
during the PMJ phase, giving a possible explanation for the enhanced emission
in the overall Ca II K profiles emerging from these transients.
