Resolution of the 2-D Grid

The parameters neta and nq specify the resolution of this thorn's 2-D grid in $\eta$ and $\theta$ respectively.^part333 The default values are a reasonable starting point, but you may need to increase them substantially if you need very high accuracy (very small constraint violations).

To help judge what resolution may be needed, this thorn has an option to write out $\psi(\eta)$ and $\psi$ on the 2-D grid to an ASCII data file where it can be examined and/or plotted. To do this, set the Boolean parameter output_psi2D, and possibly also the string parameter output_psi2D_file_name.