Sadao Masamune

Axisymmetric reduction of the adjoint operator in ideal MHD equilibrium

Adjoint formulations of magnetohydrodynamic (MHD) equilibrium are presented for sensitivity analysis and optimization-based equilibrium calculations. We derive the adjoint of the three-dimensional equilibrium equations under fixed-boundary conditions and analyse its axisymmetric reduction. The reduced operator coincides with the perturbed Grad-Shafranov operator, thereby making explicit the connection between the threedimensional adjoint construction and the axisymmetric adjoint problem. The resulting framework provides a basis for relating adjoint structures in both axisymmetric and fully three-dimensional ideal MHD equilibrium.