insu-03583346
https://insu.hal.science/insu-03583346
doi:10.1016/j.pepi.2012.03.002
[INSU] INSU - Institut National des Sciences de l'Univers
[UNIV-PARIS7] Université Denis Diderot - Paris VII
[AFRIQ] HAL-Francophonie, Afrique et océan indien
[CNRS] CNRS - Centre national de la recherche scientifique
[IPGP] Institut de Physique du Globe de Paris
[SORBONNE-UNIVERSITE] Sorbonne Université
[UNIV-PARIS] Université Paris Cité
[ALLIANCE-SU] Alliance Sorbonne Université
Investigating the 2003 geomagnetic jerk by simultaneous inversion of the secular variation and acceleration for both the core flow and its acceleration
Silva, Luís
Hulot, Gauthier
[SDU] Sciences of the Universe [physics]
ART
At observatory locations, the Earth's magnetic field displays an almost constant secular acceleration, except at times of geomagnetic jerks when this quantity suddenly changes its value. The 2003 geomagnetic jerk was the first to have been recorded globally and uniformly over the Earth, and is well captured by time-varying spherical harmonic models of the geomagnetic field, based on satellite data. We jointly derive instantaneous estimates of the core surface flow and acceleration accounting for the field secular variation and acceleration given by such models. We consider epochs just before and after the 2003 event and show that no steady flow, no matter how general, can simultaneously account for the observed secular variation and acceleration at either epoch. Assuming the flow to be tangentially geostrophic, we next show that even purely toroidal zonal flow accelerations cannot account for the observed secular acceleration and conclude that more general tangentially geostrophic flow accelerations are required by the data. These flow accelerations, however, may well be equatorially symmetric, as predicted by theoretical considerations. Investigating the flow acceleration change throughout the 2003 event shows that these also may be equatorially symmetric, but definitely not purely toroidal zonal. This unambiguously confirms earlier suggestions that the 2003 geomagnetic jerk was a more complex phenomena than a simple consequence of torsional oscillations.
2012
en
Physics of the Earth and Planetary Interiors