What are properties of the coupling between the Earths core and mantle?
Joint observations with the VLBA and the geodetic VLBI network provide the best available precision of determination of nutation angle offsets. Such observations allow the study of retrograde free core nutation, which cannot be predicted but can be determined only with VLBI. This poorly understood process has a variable amplitude with period around 430 days. Analysis of nutation amplitudes provides valuable constraints on parameters of geophysical models, such as the electromagnetic coupling on the Earth’s core-mantle boundary. • Synergies with other major forefront facilities Synergies between the VLBA and other facilities come in several forms. First there is the synergy of observing at multiple wavelengths to understand specific objects. Next there is the synergy of using multiple facilities as part of a larger instrument. Finally there is the synergy of providing enabling support for other types of observations. The VLBI technique may be viewed as one that enables high-energy astro
