HMI SHARP field inclination azimuth disambig

The segments:

field
inclination
azimuth
disambig

describe the magnetic vector in polar/inversion-style form.

Meaning

• field: total magnetic-field strength, $|\mathbf{B}|$.
• inclination: angle of the field vector relative to the reference direction.
• azimuth: direction of the transverse component in the image/tangent plane.
• disambig: information used to resolve the 180-degree ambiguity in azimuth.

This representation is common near the spectropolarimetric inversion stage, where the field naturally comes out as a magnitude plus angles.

Why disambiguation is needed

The transverse-field azimuth has a 180-degree ambiguity: two directions can explain the same polarisation signal. The disambig segment tells the pipeline which way to flip the azimuth where needed.

Without that correction, the horizontal field can point the wrong way while still looking numerically reasonable. That is a classic magnetogram footgun.

NF2 loader path

These segments are not plug-compatible with the default Br/Bp/Bt FITS path.

In this codebase they correspond to FldIncAziFITSDataset, with config keys like:

type: fld_inc_azi
fits_path:
  B_fld: path/to/field.fits
  B_inc: path/to/inclination.fits
  B_azi: path/to/azimuth.fits
  B_amb: path/to/disambig.fits

The loader converts inclination and azimuth from degrees to radians, applies the disambiguation correction, and then builds a LOS/transverse/azimuth-style representation.

Use case

Use this family for disambiguation experiments or raw vector-reconstruction work.

For the normal AR 11158 HMI SHARP CEA run, use Bt instead.

Related

• HMI SHARP CEA vector components
• CEA vectors vs polar magnetic-field representation
• NF2 segment choice for evaluations