Variational methods and core modes - Earth Dynamics: Deformations and Oscillations of the Rotating Earth - page 467

90

0

Radius

Figure 8.11 The generalised displacement potential for the retrograde equatorial
translational mode. For Earth model Cal8 it has a period of 3.5168 hours.

Azimuthal component

Meridional projection

Rotation
axis

Equator

Figure 8.12 Displacement vector field for the retrograde equatorial translational
mode. The motion parallel to the equatorial plane and projected on the meridional
plane is shown on the right, while the azimuthal motion is shown on the left in
perspective.

The programme EIGENS.FOR calculates the eigenfrequencies of core modes in
the absence of viscosity. The periods in hours for the translational triplet of modes
are listed in Table 8.1 for four Earth models.

8.6 Rotational splitting and viscosity
The translational triplet of inner core modes has been observed in a number of
spectra from superconducting gravimeter observations (Courtier et al. , 2000).