acoustic and magnetic fluxes (bottom row) calculated at the top boundary ($z=2$ Mm), though now they are normalized by the injected fast wave flux at the bottom. These are very similar to those obtained above from SPARC simulation, though the peaks of power are shifted a little in $\theta$ and $\phi$, probably because the injected flux in the simulations is not purely fast wave, since the stochastic driver is both shallow and indiscriminate in the type of waves it produces. The greater computational box height for the BVP may also contribute to the difference. It is seen that $F_{\rm ac}$ reaches over 55% and $F_{\rm mag}$ more than 40% in this case, showing that indeed, losses to the upper atmosphere can be substantial.

Total fractional loss $\mathcal{L}$ is also shown (top right). This includes both upgoing and downgoing losses from the fast wave, a quantity difficult to estimate in the SPARC simulations. In other words, the remnant reflected fast wave that ultimately rejoins the interior seismic wavefield has been reduced in power by fraction $\mathcal{L}$, which can be as high as 80%. It is notable that, as expected, $\mathcal{L}$ is more nearly symmetric about $\phi=90^\circ$ than are the upward fluxes 