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Are oscillations of the magnetospheric magnetic field responsible of oscillations of the dipole field in the core ?

par Nicolas GILLET - 7 juillet 2017

supervisors : N. Schaeffer & N. Gillet, geodynamo team, ISTerre

contact : nicolas.gillet@univ-grenoble-alpes.fr, nathanael.schaeffer@univ-grenoble-alpes.fr

summary : The dipole magnetic field is generated within the Earth’s outer core. It shows, at period about 10 years, intriguing oscillations detected in ground based observatories. The magnetospheric magnetic field also fluctuates at the same periods, influenced by the solar wind. This external field diffuses down to the core surface. There, electrical currents in the fluid iron respond to this excitation. Similarly, oscillation of the internal dipole of Mercury have recently been detected in records of the Messenger mission, at a period characteristic of the external field.

The aim of this project is to study if external fields can be responsible of such oscillations of the internal dipole fields in the cores of the Earth and Mercury. This issue will be tackled by means of a numerical code (simulating fluid motions in the presence of a magnetic field in a rotating sphere), in order to quantify the response of the fluid outer cores to an external magnetic forcing.







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