Mutual friction coefficient ﹩{{ \mathcal B }}_{{\rm{cr}}}﹩ as a function of normalized cylindrical radius x/R_oi for a 1.4 M_⊙ neutron star. (a) Dependence on the symmetry energy slope L₀ for the PKDD interaction, with no entrainment (﹩{m}_{n}^{* }/{m}_{n}=1.0﹩). (b) Dependence on the effective mass ﹩{m}_{n}^{* }/{m}_{n}﹩ for PKDD with L₀ = 40 MeV. The gray-shaded region and the gray solid vertical line mark the radial positions of the crust–core interface in the equatorial plane. Stronger entrainment (larger ﹩{m}_{n}^{* }/{m}_{{n}}﹩) significantly suppresses the crustal mutual friction coefficients.