CEA vectors vs polar magnetic-field representation

Both descriptions represent the same physical magnetic vector $\mathbf{B}$ at the lower solar atmosphere. The difference is the coordinate language used to store it.

CEA vector components

CEA SHARP data gives the vector as remapped components:

• Br: radial / local normal component.
• Bp: heliographic phi component.
• Bt: heliographic theta component.

In the NF2 FITS loader convention:

Bx = Bp
By = -Bt
Bz = Br

This is the clean path for HMI SHARP CEA extrapolation because the vector components are already resolved.

Polar representation

The polar/inversion-style representation stores the same vector as:

• field: magnitude $|\mathbf{B}|$.
• inclination: angle away from the reference direction.
• azimuth: transverse-field direction.
• disambig: mask/bit information for the 180-degree azimuth ambiguity.

This form is useful when working closer to inversion outputs or when testing disambiguation logic. It is not the default path for AR 11158 SHARP CEA runs.

Practical NF2 rule

For normal active-region HMI work, use HMI SHARP CEA vector components.

For disambiguation experiments, use HMI SHARP field inclination azimuth disambig.

Do not compare or mix the two families until they have been converted into the same component convention. Otherwise the numbers may look clean while describing different axes.

Related

• CEA projection
• HMI SHARP CEA vector components
• HMI SHARP field inclination azimuth disambig
• NF2 FITS loader component conventions
• NF2 segment choice for evaluations