B₀ field intensity computed for a n = 3, m = 1 magneto-Rossby wave in a given range of rotation period P_rot and wave periods P_nm = 2π/ω_nm, for ρ = 1 × 10⁻¹ g cm⁻¹, R_tach = 0.7 R_⊙ (top) and ρ = 1 × 10⁻³ g cm⁻¹, R_tach = 0.9 R_⋆, R_⋆ = 1.5 R_⊙ (bottom). Retrograde waves are shown in the left panel, and prograde waves are plotted in the right panel. The location of the six stars with significant spot coverage modulations is shown in black in the diagram. Each star is identified with the identifier provided in Table 1. See the main text for the explanation of the range of P_rot shown in each panel.