analysis relies additionally on a description of the ion fraction which, as discussed earlier and by Sundqvist et al. (2010) or Šurlan et al. (2012), can also be affected by large scale clumping or the presence of extremely hot wind plasma (Huenemoerder et al., 2010).

Our NAC results may also help explain the “P[v]{} discordance” in O stars. Fullerton et al. (2006) presented a compelling, independent indication of strong clumping in the wind based on the analysis of the P Cygni P[v]{} resonance line doublet in [*FUSE*]{} far-UV spectra. Because phosphorus has a low cosmic abundance, this doublet never saturates in normal OB stars, providing useful estimates of mass-loss rate when P$^{4+}$ is the dominant ion. These mass-loss rates are however considerably discordant with those inferred from other diagnostics such as H$\alpha$ and free-free emission. The most reasonable way to resolve this difference is to invoke extreme clumping in the wind. The Galactic O supergiants examined by Fullerton et al. (2006) and also the LMC stars studied by Massa et al. (2003) generally do [*not*]{} exhibit NACs in their unsaturated P[v]{} doublet lines. This absence of NACs may be explained by the ratio of ion fractions derived by Massa et 