This allows us to investigate the Earth's rheology (deformational behaviour in response to forces) at time scales intermediate between the frequencies of seismic vibrations following earthquakes (seconds to minutes) and the
Chandler wobble (an almost-regular rotational movement at near-yearly timescales).
(2002), who found that the rapid changes in the
Chandler wobble phase follow the GMJ with a delay of 1-3 years.
The wobble in Earth's axis of rotation is a combination of two major components:
Chandler wobble, thought to arise as Earth is not rigid, and another is the annual wobble, related to Earth's orbit around the sun.
* Motion of the oceans, that cause the additional forcing of polar motion (namely the excitation of the free
Chandler wobble), diurnal and sub-diurnal polar motion, and variations of the speed of rotation;
* Mystery solved: Long-term fluctuations in pressure at the ocean's bottom appear to drive the
Chandler wobble, which causes the North Pole to wander a path of about 20 feet every 14 months (158: 111).
According to Goss's calculations, based on IERS data, two-thirds of the
Chandler wobble is caused by such changes.
Earth is no exception to this general rule, although it does exhibit several tottering motions, the two most prominent being the so-called
Chandler wobble and the precession of the equinoxes.
These elements combine in an effect known as the
Chandler wobble to create polar motion.
Here [e.sub.R] denotes the dynamical ellipticity of the rigid Earth used to compute the rigid solution, [N.sub.0], [Q.sub.j] are complex "strength" parameters, and [s.sub.j] are four complex resonance frequencies corresponding to
Chandler Wobble (CW, with terrestrial period of about 435 days), retrograde FCN (with celestial period of about 430 days), Prograde Free Core Nutation (PFCN, with celestial period of about 1020 days) and Inner Core Wobble (ICW, with terrestrial period of about 2400 days), respectively.
By itself, the
Chandler wobble 0would cause the pole to move back and forth about 20 feet every 14 months.
Here [e.sub.R] denotes the dynamical ellipticity of the rigid Earth used to compute the rigid solution, [N.sub.0], [Q.sub.j] are complex constants, and [s.sub.j] are four complex resonance frequencies corresponding to
Chandler Wobble (CW, with terrestrial period of about 435 days), RFCN, with celestial period of about 430 days, Prograde Free Core Nutation (PFCN, with celestial period of about 1020 days) and Inner Core Wobble (ICW, with terrestrial period of about 2400 days) respectively.
Because of a puzzling phenomenon called the
Chandler wobble, they will probably sit about 10 meters apart.
