Quasi-geostrophic flows responsible for the secular variation of the Earth's magnetic field

By Maria Alexandra Pais, D. Jault. 2008

163 citations recorded by the source corpus.

SUMMARY We present core flows constructed from high resolution secular variation (SV) models for the epochs 2001, 2002.5 and 2004, assuming that these flows are quasi-geostrophic in the core interior and that they do not cross the axial cylindrical surface tangent to the inner core. A large jet encircling the inner core and carrying a significant part of the core angular momentum and axial vortices of ∼700 km diameter mainly clustering around the cylinder tangent to the solid inner core, are inferred from geomagnetic SV. New regularizations are suggested from dynamic considerations. It is found that medium and small-scale velocity fields contribute significantly to the large-scale SV. Accordingly, final models of core flows are calculated after an iterative process, whereby the magnetic field variation produced by small-scale stochastic magnetic fields and medium to small-scale computed velocity fields are incorporated into the inversion itself as modelling errors. This study represents a significant step in an effort to join geomagnetic observations and the fluid core dynamics on short timescales.

Subfields: Atmospheric Science, Molecular Biology, Oceanography

View Paper: https://www.semanticscholar.org/paper/9e2c5c04b8d79cc01f8be096374820ae0541e648

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Citations in the corpus

Rotating convective turbulence in Earth and planetary cores (2015, background): “Instead, cores flows must be inferred based on remote observations of the magnetic field itself (e.g., Pais and Jault, 2008).”
The CHAOS-4 Geomagnetic Field Model (2013, methodology): “Emphasized (green or red symbols) are the 43 observatories that provided quasi-definitive (cf. Peltier & Chulliat 2010) data in 2013, out of which 21 observatories (red dots with three letter code given) were used for calculating the RC index. spherical harmonic expansion coefficients vm1 of degree…”
Turbulent geodynamo simulations: a leap towards Earth's core (2017, background): “…though the intense jet localized near the tangent cylinder in S1 and S2 (see Figure 4) looks similar to the ones inferred from geomagnetic data (e.g. Pais and Jault, 2008; Schaeffer and Pais, 2011; Pais et al., 2015; Gillet et al., 2015; Livermore et al., 2016), it flows in the opposite direction.”
The Magnetic Field of Planet Earth (2010, result): “…then be symmetric with respect to the equator, an assumption that has the advantage of further reducing the non-uniqueness of the core surface flow determination, and which indeed seems to comply with the observations when considering fast changing flows (Pais and Jault 2008; Gillet et al. 2009a).”
Recent geomagnetic secular variation from Swarm and ground observatories as estimated in the CHAOS-6 geomagnetic field model (2016, background): “…and Olson 2004) and also force the flow to be equatorially symmetric, consistent with core motions that are to leading order axially invariant (Pais and Jault 2008) so that, The core surface flow is expanded into toroidal and poloidal parts where r is the position vector and T and S are…”