We consider a model for HH 111 as a jet ejected with a sawtooth, time-dependent ejection velocity. Such a variability is suggested by the position-velocity (PV) diagrams obtained from Hubble Space Telescope observations. We calculate both analytic and numerical models describing the flow resulting from such an ejection velocity time variability. Analytically, we calculate the flow for the limiting cases of massless working surfaces (i.e., those that efficiently eject mass sideways into the cocoon of the jet) and mass-conserving working surfaces, and we find that the numerically computed flow lies between these two limits. From the numerical simulations, we compute PV diagrams that can be directly compared with the corresponding observations. We find a surprisingly good agreement, which can be seen as a partial confirmation of the interpretation of the knots along HH 111 as the result of a time dependence in the ejection. Also, we show that a sawtooth functional form for the ejection velocity variability appears to be particularly appropriate for modeling the detailed radial velocity structure of the knots along HH 111.
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