Top panel: Propagation diagram of a 4G model showing the “radiative arch” due to core splitting for M_* = 0.47 M_⊙, lq_core =−0.4, lq_env =−2, X(He)_core = 0.1. N² is the Brunt-Väisälä frequency (blue), L₁ is the Lamb frequency at ℓ = 1 (green). Red horizontal lines are the log(σ²) of each mode of radial order k = 1 to 70, and red dots indicate the radial node positions in log(q). Bottom panel: Weight function of a mode trapped in the radiative arch, for the same model parameters as the top panel.