Variational methods and core modes - Earth Dynamics: Deformations and Oscillations of the Rotating Earth - page 465

90

0

Radius

Figure 8.7 Generalised displacement potential for the axial inner core transla-
tional mode. For Earth model Cal8 it has a period of 3.7926 hours.

Azimuthal component Meridional projection

Rotation
axis

Equator

Figure 8.8 Displacement vector field for the axial translational mode of the inner
core. On the left the small azimuthal component is shown in projection, while on
the right the relatively large axial motion is shown projected on the meridional
plane.

equatorial plane. The angular frequency is negative for the prograde mode, which
travels westward at the rate 2 Ω σ. The generalised displacement potential for the

prograde equatorial mode is shown in Figure 8.9. The displacement vector field
for this mode is plotted in Figure 8.10. As well as the dominant motion parallel to
the equatorial plane, as shown on the right, there is a large azimuthal component
shown on the left in perspective.