EARTH ORIENTATION

EXCITATION OF THE EARTH ROTATION
The Earth rotation undergoes changes under the influence of the lunisolar gravitational torque and various geophysical excitations. Whereas the lunisolar forcing can be well modelled as the sum of periodic terms through the Tides Generating Potential (TGP) , the geophysical excitation remains unpredictable, and has to be computed from various sets of geophysical data. In the following page we present links to time series of : Atmospheric Angular Momentum (AAM) excitation functions (routinely derived) and atmospheric torque on the solid Earth Oceanic Angular Momentum (OAM) Hydrological Angular Momentum (HAM) excitation functions Core angular momentum (CAM) associated with core-mantle electromagnetic coupling These forcings can be compared to the ones observed in polar motion (PM) and lenght of day (LOD). Here below we provide also the "observed excitation" for periods > 5-10 d, as computed from EOP combined series "C04" for PM and LOD.
Observed excitation comparison with geophysical excitation	Observed excitation for Polar Motion and UT1 derived from EOP combined series (C04) - Comparison with the NCEP-NCAR reanalysis atmospheric angular momentum time series. For instance removing of the Atmospheric/Oceanic excitations from the Excess of the length of day for geomagnetic investigations. Atmospheric excitation of the nutation
IERS Global Geophysical Fluid Center	Geophysical Fluid Excitation (AAM, OAM, HAM, CAM,...)
Atmospheric excitation	Atmospheric angular momentum : Special Bureau for the Atmosphere of GGFC of the IERS (AER, Boston) Atmospheric torque on the solid Earth Atmospheric pressure loading with a 6 hours resolution for VLBI and SLR sites : L. Petrov, J.P. Boy - GSFC
Oceanic excitation	Oceanic angular momentum : Special Bureau for the Oceans of the GGFC of the IERS (NASA/JPL)
Hydrological excitation	Hydrological excitation function : Special Bureau for the Hydrology of the GGFC of the IERS (Center for Space Research, University of Texas)
Core-mantle coupling	Axial angular momentum of the core : Special Bureau for the Core of the GGFC of the IERS (Observatoire Royal de Belgique, Bruxelles)