Signatures of Incomplete Paschen-Back Splitting in the Polarization   Profiles of the He I 10830 multiplet
  We investigate the formation of polarization profiles induced by a magnetic field in the He I multiplet at 1083,0 nm . Our analysis considers the Zeeman splitting in the incomplete Paschen-Back regime. The effects turn out to be important and produce measurable signatures on the profiles, even for fields significantly weaker than the level-crossing field ($\sim$400 G). When compared to profiles calculated with the usual linear Zeeman effect, the incomplete Paschen-Back profiles exhibit the following conspicuous differences: a) a non-Doppler blueshift of the Stokes V zero-crossing wavelength of the blue component; b) area and peak asymmetries, even in the absence of velocity and magnetic gradients; c) a $\sim$25% reduction in the amplitude of the red component. These features do not vanish in the weak field limit. The spectral signatures that we analyze in this paper may be found in previous observations published in the literature. 
H. Socas-Navarro, J. Trujillo Bueno, E. Landi Degl'Innocenti