Excitation of the Earth’s Orientation by Geophysical fluids and Geomagnetic Jerks

0539408 - ASÚ 2021 RIV FR eng C - Konferenční příspěvek (zahraniční konf.)
Ron, Cyril - Vondrák, Jan
Excitation of the Earth’s Orientation by Geophysical fluids and Geomagnetic Jerks.
Proceedings of the Journées 2017: Futhering our knowledge of Earth rotation. Paris: Observatoire de Paris, 2020 - (Bizouard, C.), s. 3-10. ISBN 978-84-1302-092-1.
[Proceedings of the Journées 2017: Futhering our knowledge of Earth rotation. Alicante (ES), 25.09.2017-27.09.2017]
Institucionální podpora: RVO:67985815
Klíčová slova: Earth’s orientation * geomagnetic jerks * geophysical excitations
Obor OECD: Astronomy (including astrophysics,space science)
https://web.ua.es/journees2017/proceedings/PROCEEDINGS-JOURNEES.pdf

It is well known that the Earth’s orientation is affected, in addition to external torques caused by the Moon, Sun and planets, also by excitation by geophysical fluids (atmosphere, oceans, and hydrology). Only very recently it was noticed that the observed changes of the amplitud and phase of the free modes (Chandler wobble, Free Core Nutation) are correlated with the rapid changes of the second time derivative of geomagnetic field, so called geomagnetic jerks (GMJ). These events occur irregularly, in intervals of several years, and last typically several months. We use Brzezinski’s broad band Liouville equations (expressed both in terrestrial and celestial reference frames) to integrate numerically the changes of Earth’s orientation due to geophysical excitations. We use standard excitations by atmosphere and oceans (hydrology being neglected), and we also add GMJ effect, modeled as impulse-like functions centered at GMJ epochs. We are able to demonstrate that the agreement of the integrated Earth orientation with the observed values significantly improves when GMJ effect is considered. This approach enables us also to determine the parameters of the free modes (period, Q-factor) with improved accuracy.
Trvalý link: http://hdl.handle.net/11104/0317158