Quality Metrics#

nf2-metrics prints a standard set of NLFF quality metrics for Cartesian and spherical checkpoints.

nf2-metrics "./runs/sharp_cea/extrapolation_result.nf2" \
  --Mm_per_pixel 0.72 \
  --height_range 0 80

For spherical checkpoints, choose the sample grid explicitly:

nf2-metrics "./runs/spherical/extrapolation_result.nf2" \
  --spherical_sampling 32 64 128 \
  --radius_range 1.0 1.3 \
  --latitude_range -60 60

--spherical_sampling is the number of samples in radius, latitude, and longitude. Larger values improve volume coverage and cost more memory/time.

Use the same sampling ranges when comparing runs. Metrics depend on the evaluated volume, so changing --height_range, --radius_range, grid spacing, or spherical sampling can change the reported values even when the checkpoint is the same.

Cartesian Quality Metrics#

nf2-metrics "./runs/sharp_cea_377/extrapolation_result.nf2" \
  --Mm_per_pixel 0.72 \
  --height_range 0 80

Spherical Quality Metrics#

nf2-metrics "./runs/spherical_hmi/extrapolation_result.nf2" \
  --spherical_sampling 32 64 128 \
  --radius_range 1.0 1.3 \
  --latitude_range -60 60

The printed metrics include mean and RMS divB, mean and RMS divB/B, current-weighted theta_J, sigma_J/CWsin, total magnetic energy E_tot, Cartesian FFT free magnetic energy E_free, and E_free/E_tot. Spherical free energy is currently reported as n/a because the implemented free-energy estimate uses a Cartesian FFT potential-field reference.

Read the metrics as diagnostics rather than pass/fail thresholds:

  • mean_abs_divB, rms_divB, mean_abs_divB_over_B, and rms_divB_over_B measure how close the field is to divergence-free. Lower is better when the same volume and sampling are used.

  • theta_J, sigma_J, CWsin, mean_force_free_residual, and rms_force_free_residual measure current-field alignment and force-free consistency. Lower values indicate better alignment.

  • E_tot is the total magnetic energy in the sampled volume. Compare it only across runs evaluated on the same physical domain.

  • E_free, E_pot, and E_free_over_E_tot estimate the non-potential energy content for Cartesian checkpoints. For spherical checkpoints these free-energy fields are reported as n/a.

  • mean_B and max_B are useful sanity checks for unit mistakes, unexpectedly weak fields, or ranges that include too much quiet volume.

For a new setup, run metrics on the analytical smoke test first, then on a small observational volume. If metrics keep improving at the end of training, increase training.epochs or data.iterations; if they are noisy or out of memory, reduce the evaluation grid or pass a smaller --batch_size.

The generated export and metrics reference lists all metric names.