Toroidal normal mode of the Earth
= Toroidal normal mode of the Earth
A <toroidal normal mode of the Earth> is a free oscillation with tangential, divergence-free displacement. It is the spherical counterpart of the transverse shear motion in a <Love wave>. A bounded spherical <Earth> has discrete angular orders and <eigenfrequencies>, so the arbitrarily low-frequency continuum of a flat infinite layer is not a literal statement about global nonrigid oscillations.