4.3.3 Emissivity

Figure 20: Grey-scale image of $\log(n_0 B^{1+\alpha})$, derived from the model emissivity, for $n_0$ in m$^{-3}$ and $B$ in T. Top: model with Gaussian profile; bottom: model with spine/shear layer. The areas covered by the two plots are not quite the same because the two models have different angles to the line of sight, but the linear scales are identical.

The spatial variation of $n_0 B^{1+\alpha }$ (proportional to the rest-frame emissivity) is shown as a grey-scale image in Fig. 20 and as longitudinal profiles in Figs 17. The emissivity is again poorly constrained in the inner region, and we can only exclude very steep decreases with distance. For the shear layer, the dependence of emissivity on distance is very different for the flaring ( $\propto \rho^{-3.1}$) and outer ( $\propto \rho^{-1.4}$) regions. The relative contribution from the spine is small, so its emissivity could vary either as a single power-law or in a manner closer to that of the shear layer. The fractional emissivity at the edge of the shear layer is consistent with a constant value of $\approx$0.2 in the flaring and outer regions, although a much wider range (including zero) is allowed at the inner boundary. There is strong evidence for a discontinuity in emissivity at the inner boundary for the shear layer.

2002-06-13