Determination of the Earth's free core nutation parameters by using tidal gravity data

摘要

@@ The Earth's free core nutation (FCN) is a retrograde eigenmode which is attributed to the interaction between the solid mantle and the liquid core of the rotational elliptical Earth. This mode appears as an eigenmode of nearly diurnal free wobble (NDFW) in a terrestrial reference frame with a period of about one day (XU et al, 2001).Therefore, the NDFW will lead to an obvious resonance enhancement in the diurnal tidal gravity observations,especially those of the tidal waves with frequencies closed to its eigenfrequency such as P1, K1, Ψ1 and Φ1.