* *helio_tools*: Minor extension of *NGSolve* providing some auxiliary tools for computational helioseismology. Can be installed analogously to

*ngs_refsol*. This extension is required only for a single experiment (computation of power spectrum for axisymmetric discretization). Users

who are not interested in this experiment can ignore this extension.

* [ngsxfem](https://github.com/ngsxfem/ngsxfem) is an add-on library to NGSolve for unfitted finite element technologies. We use some of the features that this library provides

in the experiments featuring sweeping preconditioners.

* [Ceres Solver](http://ceres-solver.org) Nonlinear least squares solver utilized for solving the optimization problem for dtn. Installation instructions

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@@ -809,8 +812,8 @@ the script `power-spectrum.py` consists of two steps.

This will produce the power spectra *power-spectrum-VALC-meshed.out* and *power-spectrum-Atmo-whitw.out*.

* If you would prefer to also compute the dtn numbers yourself, then omit the "download" flag

python3 power-spectrum.py "VALC" "download"

python3 power-spectrum.py "Atmo" "download"

python3 power-spectrum.py "VALC"

python3 power-spectrum.py "Atmo"

Afterwards please continue with the instructions given for the case of already provided data, see e.g.[here](#IntroHelioDownload). The "download" flag