High-accuracy estimation of magnetic field strength in the interstellar medium from dust polarization

Dust polarization is a powerful tool for studying the magnetic field properties in interstellar medium (ISM). However, it does not provide direct measurement of its strength. Different methods havebeen developed which employ both and spectroscopic data order to infer The most widely applied have been by Davis (1951), Chandrasekhar & Fermi (1953) (DCF), Hildebrand et al. (2009) Houde al.(2009) (HH09). They rely on assumption that isotropic turbulent motions initiate propagation Alvf\'en waves. Observations,however, indicate turbulence ISM anisotropic non-Alfv\'enic (compressible) modes may be important. Our goal develop new method estimating strength ISM, includes compressible contradict turbulence. We use simple energetics arguments take into account estimate field. derive following equation: $B_{0}=\sqrt{2 \pi\rho} \delta v /\sqrt{\delta \theta}$, where $\rho$ gas density, $\delta v$ rms velocity as derived from spread emission lines, \theta$ dispersion angles. produce synthetic observations 3D MHD simulationsand we assess accuracy our comparing true with estimates equation. find mean relative deviation $17 \%$. depend simulated model. In contrast DCF HH09 systematically overestimate produces accurate results only simulations high sonic Mach numbers.