Speaker
Description
The Davis-Chandrasekhar-Fermi (DCF) method has been widely employed to estimate the mean magnetic field strengths in astrophysical plasmas. We present a numerical study employing the DCF method along with a promising new diagnostic for studying magnetic fields -- the polarization of spectral lines caused by the Ground State Alignment (GSA) effect. We obtain synthetic polarization observations arising due to the GSA effect from 3D simulated magnetohydrodynamic (MHD) turbulence, and estimate the mean magnetic field projected on the plane of sky. We observe that the method correctly estimates the field strengths for sub- and trans-Alfve\'nic turbulence. The strength of the projected magnetic field in the plane of sky is obtained for all magnetic field inclination and azimuthal angles. We also observe a threshold for the mean magnetic field inclination angle with the line of sight of $\theta_B > 16^\circ$ for the method. We also design a polarization map filter to minimize the effects of Van Vleck degeneracy. The spectropolarimetry combined with spectrometry from the same atomic/ionic lines not only traces the 3D direction of local magnetic field, but also improves the accuracy of the DCF method by ensuring the same origin for the magnetic field and velocity fluctuations.
