We present the analysis of the magnetic field (B-field) structure of
galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric
observations. We use the first data release of the Survey on extragALactic
magnetiSm with SOFIA (SALSA) of 14 nearby (<20 Mpc) galaxies with resolved (5
arcsec-18 arcsec; 90 pc--1 kpc) imaging polarimetric observations using
HAWC+/SOFIA from 53 to 214 \um. We compute the magnetic pitch angle
(ΨB​) profiles as a function of the galactrocentric radius. We introduce
a new magnetic alignment parameter (ζ) to estimate the
disordered-to-ordered B-field ratio in spiral B-fields. We find FIR and
radio wavelengths to not generally trace the same B-field morphology in
galaxies. The ΨB​ profiles tend to be more ordered with galactocentric
radius in radio (ζ6cm​=0.93±0.03) than in FIR
(ζ154μm​=0.84±0.14). For spiral galaxies, FIR B-fields
are 2−75\% more turbulent than the radio B-fields. For starburst galaxies,
we find that FIR polarization is a better tracer of the B-fields along the
galactic outflows than radio polarization. Our results suggest that the
B-fields associated with dense, dusty, turbulent star-forming regions, those
traced at FIR, are less ordered than warmer, less-dense regions, those traced
at radio, of the interstellar medium. The FIR B-fields seem to be more
sensitive to the activity of the star-forming regions and the morphology of the
molecular clouds within a vertical height of few hundred pc in the disk of
spiral galaxies than the radio B-fields.Comment: 26 pages, 13 figure