  The application of high-temperature superconductors to accelerator magnets
for future particle colliders is under study. Numerical methods are crucial for
an accurate evaluation of the complex dynamical behavior of the magnets,
especially concerning the magnetic field quality and thermal behavior. We
present a coupled $\textbf{A}$-$\textbf{H}$ field formulation for the analysis
of magneto-thermal transients in accelerator magnets. The magnetic field
strength $\textbf{H}$ accounts for the eddy current problem in the source
regions containing the superconducting domains, while the magnetic vector
potential $\textbf{A}$ represents the magnetoquasistatic problem in the normal
and non-conducting domains. Furthermore, we include a slab approximation for
the source regions, making the formulation suitable for large scale models
composed of thousands of tapes. In this work, the relevant equations are
derived and discussed, with emphasis on the coupling conditions. The weak
formulation is derived, and numerical results are provided in order to both,
verify the formulation and scale it to the size of an accelerator magnet.
