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itsmoosh · Jun 21, 2021 · 299c55c · 299c55c
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+# Supplemental Materials for "An analytic solution for evaluating the magnetic field induced from an arbitrary, asymmetric ocean world"
+Python software for evaluating magnetic fields from asymmetric ocean moons. Written in Python 3.8. For help, please contact M. Styczinski at [[email protected]](mailto:[email protected]).
+
+## Quick start
+* Run the file `run_all.py` using a Python 3 interpreter.
+
+You will need the following Python modules:
+* numpy
+* matplotlib
+* skyfield
+* mpmath
+* scipy
+* cartopy
+* multiprocessing
+
+To generate contour plots showing the asymmetric layer geometry, you will need to edit line 23 in `run_all.py`. These plots take a long time to generate, so they are turned off by default. Animations are set to plot differences in the magnitudes by default. Change this by setting `gif_comp = "x"`, `"y"`, or `"z"` at line 19 in the same file.
+
+## Configuration
+Run settings are split between `run_all.py`, `config.py`, `eval_induced_field.py`, and `plotting_funcs.py`.
+* `run_all.py`: Set which bodies to run, whether to plot animation frames, etc.
+* `config.py`: Set plot resolutions, precision for calculations, altitudes for magnetic field maps, date/time for evaluation, etc.
+* `eval_induced_field.py`: Set body radii, maximum shape harmonic degree p, and other normalizations.
+* `plotting_funcs.py`: Plot labels, image types, and contour/colormap settings are found within individual plotting functions.
+
+## Editing interior models
+Interior models are generated using [PlanetProfile](https://github.com/vancesteven/PlanetProfile). The specific PlanetProfile run files (called `PP<Body>_asymmetry.m`) used to create the interior conductivity profiles used in this work are contained in the `interior/PP_models/` directory. A modified version of the main PlanetProfile function is contained in `interior/PP_models/PlanetProfile_snapshot.m`. A future version of PlanetProfile will incorporate the changes contained in this file, which are primarily to interpolate the detailed ocean conductivity profile down to just 3 layers (and condense nonconducting layers).
+
+To create a conductivity profile, run a `PP<Body>_asymmetry.m` file from the appropriate (`<Body>/`) directory in your PlanetProfile installation, with `PlanetProfile_snapshot.m` replacing the main `PlanetProfile.m` file. Then, edit the final value in each row of the printed file `interior_model_asym_<Body>.txt` to match the desired asymmetry. These values are ε<sub>l</sub>/r̅<sub>l</sub> as discussed in Section 4.1.2 of the paper. Last, move the edited file to the `interior/` directory here.
+
+### Creating asymmetric shape files
+1. Collect real-valued, Schmidt semi-normalized harmonic coefficients into a single file in interior/ named `depth_chi_pq_shape_<Body>.txt`.
+   * See the corresponding file for Miranda for an example. These values are assumed to be layer thicknesses, i.e. depths from the surface to the top of an ocean.
+   * The default settings in `eval_induced_field.py` apply these coefficients to the layer with index `r_io`, which is negative. For bodies with no ionosphere, typically `r_io` is -2, the second-to-top layer.
+1. In config.py, set `relative = False` and `convert_depth_to_chipq = True` and run a field calculation (e.g. `python run_all.py` at the terminal). This prints a new file, `interior/chi_pq_<Body>.txt`.
+   * The results of this calculation will only apply asymmetry to the layer corresponding to `r_io`.
+1. Open the new file and the corresponding `interior_model_asym_<Body>.txt` file. For each concentric ocean layer, set the ε<sub>l</sub>/r̅<sub>l</sub> values to be the bcdev value reported at the end of the header line of `chi_pq_<Body>.txt` divided by the radius of the layer corresponding to `r_io`.
+   * For example, for Miranda `bcdev = 39120.39 m` and `r_io = -3` as it has an ionosphere. The radius of that boundary is 185989.764 m, so the ε<sub>l</sub>/r̅<sub>l</sub> value to use is 39120.39 / 185989.764 = 0.21. Each layer should have the same value here if they are concentric--the absolute asymmetry is scaled to the radius of the boundary.
+1. For each degree p up to the desired pmax, create a file in `interior/` named `degree<p>_shapes_<Body>.txt` and add a single descriptive header line to each.
+   * See the corresponding Miranda files for examples.
+1. Copy the lines of the `chi_pq_<Body>.txt` file for each harmonic *multiple times* into the corresponding `degree<p>_shapes` files, with one line for each layer in `interior_model_asym_<Body>.txt`.
+   * If desired, these coefficients (the χ<sup>l</sup><sub>pq</sub> values) may be adjusted to specify asymmetric layers independently.
+1. In `config.py`, set `relative = True`. Executing `run_all.py` will now use the values in `degree<p>_shapes` and `interior_model_asym` files to set the asymmetry for each layer.