HR: 09:00h
AN: G21A-05 INVITED     [PDF]
TI: Improvements in understanding the Earth's nutations and the roles of solid and fluid layers
AU: * Mathews, P M
EM: indi4272@yahoo.com
AF: University of Madras, Department of Theoretical Physics, (Guindy Campus), Chennai, Tam 600025 India
AB: Continuing improvements in the precision of nutation estimates from observational data necessitate a fresh look at recent theoretical treatments with the twin objectives of achieving a better accounting of the data and possibly obtaining more insights into the geophysical properties and processes that affect nutations. Against this background, we make a reassessment of the geophysical model underlying the MHB2000 theory and of the approximations employed. For instance, could the viscosity of the core fluid have a nonneglible influence on nuation, and if so, could inclusion of viscosity in the modeling help to reduce the electrical conductivity required for the lowermost mantle layer or magnetic field at the boundaries of the fluid core? Conversely, could the nutation data help to place useful bounds on the fluid viscosity? The last question is of particular interest in view of the very high values inferred in the recent past from studies on Slichter (translational) modes of the inner core. Other possibilities for fine tuning nutation theory relate to the potential for better modeling of the effects of ocean tides and of the atmosphere. Besides considering these, a review of the effects arising from nonlinear terms in the equations of nutation theory will be made. Finally, one needs to consider whether estimates for nutations might be ``contaminated'' by ``leakage'' from other phenomena (e.g., tides) due to possible deficiencies in their modeling in the VLBI data processing software, or for other reasons.
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1239 Rotational variations
SC: Geodesy [G]
MN: 2003 Fall Meeting