Observational Determination of the Turbulent Ambipolar Diffusion Scale and Magnetic Field Strength in Molecular Clouds

TL;DR

This paper observationally determines the turbulent ambipolar diffusion scale and magnetic field strength in a molecular cloud, providing insights into turbulence dissipation and magnetic influence in star formation regions.

Contribution

It introduces a method to measure the turbulent ambipolar diffusion scale and magnetic field strength directly from molecular line observations.

Findings

Ambipolar diffusion occurs at a scale of about 17 milliparsecs.

Magnetic field strength in DR21(OH) is approximately 1.7 milligauss.

Turbulent energy dissipation is linked to ambipolar diffusion at specific scales.

Abstract

We study the correlation of the velocity dispersion of the coexisting molecules H13CN and H13CO+ and the turbulent energy dissipation scale in the DR21(OH) star-forming region. The down-shift of the H13CO+ spectrum relative to H13CN is consistent with the presence of ambipolar diffusion at dissipation length scales that helps the process of turbulent energy dissipation, but at a different cut-off for ions compared to the neutrals. We use our observational data to calculate a turbulent ambipolar diffusion length scale L'\simeq17 mpc and a strength of B_{pos}\simeq1.7 mG for the plane of the sky component of the magnetic field in DR21(OH).