2018ApJ...862...42T

The line width of ions has been observed to be systematically narrower than that of the coexisting neutrals in molecular clouds and been interpreted as the signature of the decoupling of the neutral turbulence from magnetic fields in partially ionized medium. As a sequel of Li & Houde, here we present further observational evidence that supports these earlier proposals with the velocity coordinate spectrum analysis. We recover the turbulent energy spectra of HCN and HCO⁺ (4 - 3) in a starless molecular cloud in NGC 6334 where magnetic fields play a dynamically important role. Our analysis showed that the neutral spectrum is consistent with Kolmogorov type (k^–5/3, where k is the wavenumber), while that of the ions is the same on the large scale, but steeper (∼k^–2), for scales smaller than 0.404 pc. We carefully ruled out the possibilities that the spectrum difference can stem from the differences of ion and neutral optical depth and hyperfine structure.