Total kinetic energy density of the librationally induced core flow as a function of the forcing frequency ω near Mercury’s observed libration frequency, ω = 0.67, indicated in each plot by the black vertical line. The top row gives the core response to the three types of libration forcing, m = 0 and ±2, in a neutrally stratified core (N ₀ = 0 and r _ICB = 0.4), and the bottom row shows the response in a core with an outer stably stratified layer (N ₀ = 100, r _ICB = 0.4, r _C = 0.7, and h = 0.1). Different colored lines correspond to different Ekman numbers: Ek = 10⁻⁷ (blue), 10⁻⁸ (orange), and 10⁻⁹ (gray).