Probing the Turbulence Dissipation Range and Magnetic Field Strengths in Molecular Clouds

TL;DR

This paper investigates turbulence dissipation and magnetic field strengths in molecular clouds by analyzing velocity dispersion spectra of ions and neutrals, revealing a decoupling scale due to ambipolar diffusion.

Contribution

It introduces a novel method to estimate magnetic field strength by examining ion-neutral turbulence spectra and identifies the ambipolar diffusion scale in molecular clouds.

Findings

Ion spectra are shifted relative to neutral spectra, indicating ambipolar diffusion.

The decoupling scale can be used to estimate magnetic field strength.

The method provides new insights into turbulence and magnetic fields in star-forming regions.

Abstract

We study the turbulent velocity dispersion spectra of the coexistent HCN and HCO+ molecular species as a function of length scale in the M17 star-forming molecular cloud. We show that the observed downward shift of the ion's spectrum relative to that of the neutral is readily explained by the existence of an ambipolar diffusion range within which ion and neutral turbulent energies dissipate differently. We use these observations to evaluate this decoupling scale and show how to estimate the strength of the plane-of-the-sky component of the embedded magnetic field in a completely novel way.