A new method for probing magnetic field strengths from striations in the interstellar medium

TL;DR

This paper introduces a novel observational method to measure magnetic field strengths and their temporal evolution in molecular cloud striations, validated through simulations and applied to Taurus cloud data.

Contribution

The study develops a new technique combining molecular and dust observations to probe magnetic fields and their dynamics in interstellar striations, supported by simulations.

Findings

Magnetic field strength in Taurus is estimated at 27 ± 7 μG.

The ratio of fluctuating to ordered magnetic field components is approximately 10%.

The method shows good agreement with previous magnetic field estimates.

Abstract

Recent studies of the diffuse parts of molecular clouds have revealed the presence of parallel, ordered low-density filaments termed striations. Flows along magnetic field lines, Kelvin-Helmholtz instabilities and hydromagnetic waves are amongst the various formation mechanisms proposed. Through a synergy of observational, numerical and theoretical analysis, previous studies singled out the hydromagnetic waves model as the only one that can account for the observed properties of striations. Based on the predictions of that model, we develop here a method for measuring the temporal evolution of striations through a combination of molecular and dust continuum observations. Our method allows us to not only probe temporal variations in molecular clouds but also estimate the strength of both the ordered and fluctuating components of the magnetic field projected on the plane-of-the-sky. We benchmark our new method against chemical and radiative transfer effects through two-dimensional magnetohydrodynamic simulations coupled with non-equilibrium chemical modelling and non-local thermodynamic equilibrium line radiative transfer. We find good agreement between theoretical predictions, simulations and observations of striations in the Taurus molecular cloud. We find a value of $\rm{27 \pm 7} ~\rm{\mu G}$ for the plane-of-sky magnetic field, in agreement with previous estimates via the Davis-Chandrasekhar-Fermi method, and a ratio of fluctuating to ordered component of the magnetic field of $\sim$ 10\%.