sional frequencies) of the electrons and ions must be short compared with the size of the system ($\tau_{mat} \sim L/\lambda_{mat} \gg 1$). Table 1 shows that this condition is easily satisfied in both stellar jets and the laboratory experiments.

The Euler equations do not include the radiative energy flux, and so we must verify that this number is small compared with the hydrodynamical energy flux. When, as in our experiments, the minimum radiation mean free path $\lambda_{rad}$ from Thomson scattering or thermal bremsstrahlung is short compared to $L$ (i.e., $\tau_{rad}
\sim L/\lambda_{rad} \gg 1$), the appropriate dimensionless parameter for determining the importance of radiation is the Boltzmann number Bo\# $\sim \rho U^3 / f_{rad}$, where $U$ is a velocity scale and $f_{rad}$ is the radiative flux. In the Omega experiments, Bo\# $>>$ 1, implying that the radiative energy flux is unimportant in the flow dynamics. Radiative fluxes are also negligible in optically thin astrophysical shocks like those in stellar jets. Even in the brightest jets the observed radiative luminosity is $\lesssim$ $10^{-3}$ of the energy of the bulk flow [@bbm81], so the observations and experiments are consistent with regard to radiative energy flux.

Finally, stellar jets have magnetic fields while our experiments do not. Field strengths within stellar jets are difficult to measure, but could dominate the flow dynamics close to the acceleration region [i.e., V$_{Alfven}$ $<$ V$_{flow}$ @hartigan07]. At the larger distances of interest to these experiments, fields are weaker and act mainly to reduce compression in the postshock regions of radiatively-cooling flows [@morse92].

In summary, the experiments are good analogs of jets from young stars. The Mach numbers of the jet relative to the ambient medium and to the obstacle are high in both cases, the density contrasts between the jet and the obstacle are similar, and the scaled times match almost exactly. Both systems behave like fluids, and viscosity, thermal conduction, and r