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\subsection{Mass-loss rates}  The measured mass loss rates in the outflows from CTTS vary widely between objects. Even for a single object, very different mass loss rates can be found, depending on the spectral tracers chosen and on the assumptions used to calculate mass loss rates from line fluxes. The filling factor that describes the fraction of the observed volume occupied by hot gas is especially uncertain because the innermost jet component is generally not resolved. Also, measurements of the mass loss in a jet are possible only where the jet emission is not dominated by that of the much brighter central star.   Typical mass loss rates found in the literature for CTTS outflows are in the range $10^{-10}-10^{-6}M_{\odot}\textrm{ yr}{-1}$ \citep{1999A&A...342..717B,2006A&A...456..189P}. No outflow at all is detected in non-accreting, disk-less T Tauri stars (weak-line TTS or WTTS), For example,  \citet{2006ApJ...646..319E} measure values down to $10^{-10}$~M$_{\odot}$~yr$^{-1}$ for some CTTS, but only upper limits for WTTS. weak-line T Tauri stars (or WTTS).  In the specific case ofthe well-studied jet from  DG~Tau \citet{1997A&A...327..671L} calculate the mass loss rate as $6.5\cdot 10^{-6}$~M$_{\odot}$~yr$^{-1}$; \citet{1995ApJ...452..736H} obtain $3\cdot 10^{-7}$~M$_{\odot}$~yr$^{-1}$ and, further out in the jet, \citet{2000A&A...356L..41L} find $1.4\cdot 10^{-8}$~M$_{\odot}$~yr$^{-1}$.   \citet{2009A&A...493..579G} show that a mass loss below $10^{-10}$~M$_{\odot}$~yr$^{-1}$ is sufficient to explain the X-ray emission from the jet as shock heating, and it is possible that the optical jet further out entrains some disk wind material, so it might not track the stellar mass loss correctly.  We use $10^{-8}$~M$_{\odot}$~yr$^{-1}$ as fiducial stellar mass loss in the remainder of the article. This will contribute only a fraction to the total mass loss of the system, since the disk wind, though slower, operates over a much larger area.