Radial vorticity ζ_r eigenfunctions at the surface (r = 0.985 R_⊙) for m = 8. Left and right panels: cases for the equatorial Rossby modes with no radial nodes (n = 0) and with one radial node (n = 1). Upper and lower panels: cases with weak diffusion (ν = 10¹¹ cm² s⁻¹) and strong diffusion (ν = 10¹² cm² s⁻¹). Black solid and dashed lines represent real and imaginary eigenfunctions, respectively. The real part of the eigenfunctions are defined to be zero at the equator. The vertical red lines denote the location of critical latitudes where the phase speed of a Rossby mode is equal to the differential rotation velocity.