8. Glossary

Body Tide

see Solid Earth Tide

Chandler Wobble

small, semi-periodic deviations in the motion of the pole of rotation

Epoch

fixed point in time used as a reference value

Flattening

ratio of the difference between the semi-major and semi-minor axes of an ellipsoid to the semi-major axis

Free Core Nutation

nearly diurnal deviations in the motion of the pole of rotation due to the resonant motion of the Earth’s core relative to the mantle

Geopotential

the Earth’s gravitational potential

Geoid

equipotential surface coinciding with the ocean surface in the absence of astronomical or dynamical effects

Love and Shida Numbers

dimensionless parameters relating the vertical (h), horizontal (l) and gravitational (k) elastic responses to tidal loading

Nutation

short-period oscillations in the motion of the pole of rotation of a freely rotating body

Polar Motion

irregular motion of the Earth’s pole of rotation relative to the Earth’s crust

Pole Tide

apparent tide due to variations in the Earth’s axis of rotation about its mean

Precession

regular conical motion of the pole of rotation of a freely rotating body

Solid Earth Tide

deformation of the solid Earth due to gravitational forces

Tilt Factor

Combination of Love/Shida numbers describing the displacement of the Earth’s ocean surface with respect to the Earth’s deformed crust