1/f noise in spherical dynamo simulations

M. FONTANA, P. MININNI, P. DMITRUK

Conferencia; COLAGE XI - Eleventh Latin American Conference on Space Geophysics; 2018

For the last 70 years, it has been commonly accepted that Earth?s magnetic fieldsuffers non-periodic reversals (sudden polarity changes in the component of the dipole momentparallel to Earth?s rotation axis), as it represents the simpler mechanism to explain featuresobserved in paleomagnetic studies . The most salient ingredients of the geomagnetic field, in-cluding reversals, have been successfully reproduced in simulations by solving the equations ofthe magnetohy drodynamic (MHD) framework inside a spherical shell with appropriate bound-ary conditions. Aditionally, frequency domain analysis of dipole moment paleomagnetic recordsshows a region with a distinct 1/ f trend . This spectral functional form is associated with scaleinvariance and long-term memory in the system, and has been reported to emerge in idealmagnetohydrodynamics as a consequence of the nonlocal interactions between length scales.Employing direct numerical simulations, we show here that the aforementioned 1/ f behaviorin the dipole moment can be reproduced in non-ideal MHD for almost the entire region ofparameter space explored. Moreover, by testing two different, but steady, forcing geometries,we were able to simulate both small scale and mostly dipolar dynamos.