On the Ambipolar Diffusion Timescale and the Location of Star Formation in Magnetic Interstellar Clouds - Setting the Record Straight

The point of a recent (1983) paper by Scott is that a previous paper (1979) by Mouschovias has concluded "erroneously" that star formation takes place off center in a cloud because of the use of an "improper" definition of a time scale for ambipolar diffusion. No such conclusion, Scott claims, follows from a "proper" definition, such as the "traditional" one by Spitzer. (i) Scott misrepresents the reasoning that led to the conclusion in the paper which he criticizes. (ii) He is also wrong: both the "traditional" and the "improper" definitions vary similarly with radius, and both can have an off-center minimum; the spatial variation of the degree of ionization is the determining factor not the specific value of the time scale at the origin, as Scott claims.