Shear speed ﹩v_{s}﹩ (solid line) and Alfvén speed ﹩v_{\mathrm{A}\,}﹩ using ﹩B=3\times 10^{14}﹩ (dot‐dashed line), ﹩6\times 10^{14}﹩ (dotted line), and 10¹⁵ G (dashed line). We use the crustal compositions of Haensel & Pichon (1994) for ﹩\rho < 4\times 10^{11}\,\mathrm{g}\,\,\mathrm{cm}\,^{-3}﹩ and Douchin & Haensel (2001) for ﹩\rho > 4\times 10^{11}\,\mathrm{g}\,\,\mathrm{cm}\,^{-3}﹩.