deletions | additions       diff --git a/subsectionWind_clumpinglabelclumping.tex b/subsectionWind_clumpinglabelclumping.tex  index 0dfd270..ad607e9 100644  --- a/subsectionWind_clumpinglabelclumping.tex  +++ b/subsectionWind_clumpinglabelclumping.tex 
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\subsection{Wind clumping}\label{clumping}  Observational evidence exists for stellar wind inhomogeneities on small  and on large scales. While the latter will be discussed in Sect.~\ref{magnetic},  here we consider only small scale wind structure, or wind clumping.  In Sect.~\ref{micro}, we discussed that waves produced by the FeCZ could lead to velocity fluctuations at the stellar surface.  In order to induce wind clumping, those waves should induce density fluctuations  at the stellar surface. Through the occurrence of porosity or shifts in the ionisation  balance of the gas the mass-loss rate may be affected.   For this to happen, the amplitude of the velocity   fluctuations at the surface should be on the same order of the sound speed.   Alternatively, the velocity fluctuations  might directly affect the local mass-loss rate through the Doppler effect,  if the amplitude of the velocity fluctuations is on the same order  as the speed of the wind flow, which, at the base of the wind, is approximately   the sound speed. As the sound speed at the surface in our  massive main sequence models is on the order of a few times $10\kms$,  we consider here those stellar models potentially capable to produce wind  clumping for which the convective velocities  in the upper part of the FeCZ $\vca \geq 2.5\kms$,  as this allows energetically to have surface velocity amplitudes  above $\sim 10\kms$ (cf. Sect.~\ref{micro}).