Detailed Analysis of Diurnal Tides and Associated Space Nutation in the Search of the Free Inner Core Nutation Resonance

International audienceWe propose a comparison of the tidal analysis results obtained from the continuous records of time-varying surface gravity collected by a worldwide network of Superconducting Gravimeters with the analysis results of space nutation observed by the international Very Long Baseline Interferometry (VLBI) network. The length of the surface gravity time series (20 years for the longest) enables now to look for additional diurnal tides that were previously not analyzed. In parallel, we now possess 35 years of VLBI data permitting to look for additional nutation terms. We focus our analysis on the diurnal prograde frequency band in the search for a possible resonance effect linked to the Free Inner Core Nutation. This Earth's normal mode has never been clearly observed. Its direct deformation effect at the Earth’s surface is theoretically predicted to be too small to be detected. However, the tidal forcing at a frequency close to its eigenfrequency could enhance some tidal or nutation amplitude resulting in the characterization of this mode through its resonance effect