vmec_jax.vmec_bcovar

VMEC-style half-mesh metric + B-covariant ingredients.

This module ports the core algebra from VMEC2000’s bcovar for fixed-boundary parity work:

• Build half-mesh metric elements g_uu, g_uv, g_vv using VMEC’s even/odd-m decomposition and half-mesh staggering.

• Build half-mesh Jacobian-related fields via vmec_jax.vmec_jacobian.

• Compute VMEC contravariant field components (B^u, B^v) and the covariant components (B_u, B_v) on the radial half mesh.

• Provide force-kernel inputs used by VMEC’s forces routine.

The implementation here is intentionally limited to what’s needed for validated parity work. Use use_vmec_synthesis=True to switch the internal R/Z/L synthesis to VMEC’s symmetry-reduced theta grid (ntheta2/ntheta3) using the fixaray trig tables.

Functions

vmec_bcovar_half_mesh_from_wout(*, state, ...)

Compute VMEC-style half-mesh metric and B components for parity tests.