Period and Q-Factor of Free Core Nutation, Based on Different Geophysical Excitations and VLBI Solutions

0537141 - ASÚ 2021 RIV CZ eng J - Journal Article
Vondrák, Jan - Ron, Cyril
Period and Q-Factor of Free Core Nutation, Based on Different Geophysical Excitations and VLBI Solutions.
Acta geodynamica et geomaterialia. Roč. 17, č. 2 (2020), s. 207-215. ISSN 1214-9705. E-ISSN 2336-4351
Institutional support: RVO:67985815
Keywords : rotation of the Earth * geophysical excitations * geomagnetic jerks
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 1.176, year: 2020
Method of publishing: Open access

Three variants of geophysical excitations and seven different VLBI solutions of celestial pole offsets (CPO) are used to determine period and Q-factor of Free Core Nutation (FCN). Brzezinski's broad-band Liouville equations (Brzezinski, 1994) are numerically integrated to derive geophysical effects in nutation in time domain. Possible effect of geomagnetic jerks (GMJ) is also considered. Best-fitting values of FCN parameters are estimated by least-squares fit to observed CPO, corrected for the differences between the FCN parameters used in IAU 2000 model of nutation and newly estimated ones, MHB transfer function is used to compute these corrections. It is demonstrated that different VLBI solutions lead to FCN parameters that agree on the level of their formal uncertainties, but different models of geophysical excitations change the results more significantly. Using GMJ excitations always brings improvement of the fit between integrated and observed CPO. The obtained results show that the best fit is achieved when only GMJ excitations are used. Our conclusion is that GMJ are very probably more important for exciting FCN than the atmosphere and oceans. Empirical Sun-synchronous correction, introduced in the present IAU 2000 nutation model, cannot be explained by diurnal atmospheric tidal effects.
Permanent Link: http://hdl.handle.net/11104/0314892