Reference data

Aragog's entropy solver requires a directory of pressure-entropy (P-S) equation-of-state tables. This page documents the file format, the canonical PALEOS data source, and the optional external mesh file used when the structure profile is supplied from outside (typically by the Zalmoxis structure solver).

Pressure-entropy EOS tables

The directory passed to EntropySolver.from_file(eos_dir=...) (or referenced through PROTEUS) must contain ten files in the SPIDER-format \((P, S)\) layout:

Quick start: bundled test data

A small SPIDER-format set is published as a release asset and used by the nightly CI. It is the fastest way to follow the first-run tutorial without a full PROTEUS / PALEOS install:

mkdir -p /tmp/aragog-test-data
curl -sL -o /tmp/spider_eos.tar.gz \
    https://github.com/FormingWorlds/aragog/releases/download/test-data-v1/spider_eos_test_data.tar.gz
tar xzf /tmp/spider_eos.tar.gz -C /tmp/aragog-test-data/

The unpacked directory /tmp/aragog-test-data/spider_eos/ is a drop-in eos_dir. Set ARAGOG_TEST_EOS_DIR=/tmp/aragog-test-data/spider_eos so the gated unit + smoke tests pick it up automatically.

File layout

The 2D tables follow SPIDER's text format: a header followed by a flat list of three-column \((P, S, Q)\) rows on a regular pressure-entropy grid. The first header line carries the row count and grid dimensions in the form # n_header n_P n_S. The last header line carries three SI scaling factors # P_scale S_scale Q_scale that the loader multiplies into each non-dimensional column to recover SI units (pressure in Pa, entropy in J/kg/K, value in the property's SI unit). Inside the data block the entropy axis varies slowest and the pressure axis varies fastest, so the flat list contains \(n_S\) blocks of \(n_P\) rows each.

The solidus_P-S.dat and liquidus_P-S.dat files are two-column \((P, S)\) in the same convention (header with scaling factors, then non-dimensional values), with \(P\) monotonically increasing.

The grid must be rectangular: phase-filtered tables (where each phase's grid is restricted to its own valid region) cause scipy.interpolate.RegularGridInterpolator to fall back to slow unstructured interpolation and should not be used.

Canonical source: PALEOS

In the PROTEUS coupled path the tables are produced by the PALEOS multiphase EOS framework (Attia et al. (2026)¹) from a configured P-T melting curve and the Wolf & Bower (2018)² RTpress liquid EOS. The PROTEUS wrapper writes the resulting tables into output/data/aragog_pt/ at construction time and points eos_dir there.

External mesh file (eos_method = 2)

When the mesh eos_method is set to 2, Aragog reads a four-column external file and uses it for the pressure, density, and gravity profiles instead of the analytic Adams-Williamson EOS:

The radius column must be monotonically increasing and span at least 75% of the mantle thickness \(D = R_\mathrm{outer} - R_\mathrm{inner}\). This is a coverage tolerance on the external table, not a statement that the structure is only defined over part of the domain. Aragog's own mesh always covers the full mantle shell; the 75% guard allows the external EOS table to undershoot the mantle bounds by up to 25% without raising (typical use: a resumed run where the Zalmoxis re-solve disagrees with the saved mesh at the single-ULP level near the outer/inner radii). Across that small gap np.interp extrapolates linearly from the nearest in-range value. A table that covers less than 75% is rejected with External EOS radius range ... inconsistent with mesh bounds ... because at that point the disagreement is no longer a numerical-precision artefact.

The PROTEUS wrapper writes this file from the Zalmoxis structure solver into output/data/zalmoxis_output.dat (Zalmoxis path) or output/data/spider_mesh.dat (SPIDER-static path). When eos_method = 2 the per-node gravity column overrides the scalar gravitational_acceleration config key, so the mixing-length theory and the gravitational-separation flux pick up the radial dependence of \(g\) automatically.

Adams-Williamson EOS (eos_method = 1)

The default pressure profile is analytic Adams-Williamson:

closed under constant gravitational acceleration. Parameters are set in the [mesh] section:

The Adams-Williamson path requires no external data and is the default for standalone testing.

Configuration keys at a glance

The relevant configuration keys are summarised here for cross-reference; the full schema is in How-to: configuration.