Fast equatorial waves propagating at the top of the Earth's core

Since 2000, magnetic field variations originating in the core have been dominated by several pulses in the secular acceleration, leading to sharp geomagnetic “jerks” at the Earth's surface. Using models built from (i) Defense Meteorological Satellite Program data and (ii) Ørsted and Swarm satel...

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Bibliographic Details
Published in:Geophysical research letters 2015-05, Vol.42 (9), p.3321-3329
Main Authors: Chulliat, Arnaud, Alken, Patrick, Maus, Stefan
Format: Article
Language:English
Subjects:
Acceleration
Atmospheric models
Compatibility
Construction
Decomposition
Defense programs
Density
Density stratification
Earth
Earth core
Earth science
Earth surface
Earth's core
Equatorial waves
Geomagnetic field
Geomagnetic fields
geomagnetic jerks
Geomagnetism
Geophysics
Magnetic field
Magnetic fields
Meteorological satellite program
Meteorological satellites
Modes
Ocean currents
Planetary waves
Propagation
Propagation modes
Remote sensing
Rossby waves
Satellite observation
Satellites
secular variation
Spaceborne remote sensing
Stratification
Swarm
Symmetry
Wave propagation
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Summary:Since 2000, magnetic field variations originating in the core have been dominated by several pulses in the secular acceleration, leading to sharp geomagnetic “jerks” at the Earth's surface. Using models built from (i) Defense Meteorological Satellite Program data and (ii) Ørsted and Swarm satellites and ground observatory data, we show that a new pulse occurred in 2012.5, immediately following two pulses in 2006 and 2009. The three pulses can be decomposed into several equatorially symmetric modes propagating eastward and westward at 550 to 1100 km/yr, and one equatorially antisymmetric mode propagating eastward at 1650 km/yr. The characteristics of these modes are compatible to some extent with equatorial magnetic Rossby waves propagating within a 140 km thick layer at the top of the core with a density contrast of 50 ppm. This interpretation, if confirmed, would provide a new explanation for geomagnetic jerks and pulses based on stable stratification of the core. Key Points A new secular acceleration pulse occurred in 2012.5 Recent pulses are decomposed in fast equatorial waves at the core surface Waves have characteristics of magnetic Rossby waves in a stratified layer
ISSN:0094-8276
1944-8007
DOI:10.1002/2015GL064067