TY  - JOUR
A1  - Bärenzung, Julien
A1  - Holschneider, Matthias
A1  - Lesur, Vincent
T1  - constraints
T2  - Journal of geophysical research : Solid earth
N2  - Prior information in ill-posed inverse problem is of critical importance because it is conditioning the posterior solution and its associated variability. The problem of determining the flow evolving at the Earth's core-mantle boundary through magnetic field models derived from satellite or observatory data is no exception to the rule. This study aims to estimate what information can be extracted on the velocity field at the core-mantle boundary, when the frozen flux equation is inverted under very weakly informative, but realistic, prior constraints. Instead of imposing a converging spectrum to the flow, we simply assume that its poloidal and toroidal energy spectra are characterized by power laws. The parameters of the spectra, namely, their magnitudes, and slopes are unknown. The connection between the velocity field, its spectra parameters, and the magnetic field model is established through the Bayesian formulation of the problem. Working in two steps, we determined the time-averaged spectra of the flow within the 2001–2009.5 period, as well as the flow itself and its associated uncertainties in 2005.0. According to the spectra we obtained, we can conclude that the large-scale approximation of the velocity field is not an appropriate assumption within the time window we considered. For the flow itself, we show that although it is dominated by its equatorial symmetric component, it is very unlikely to be perfectly symmetric. We also demonstrate that its geostrophic state is questioned in different locations of the outer core.
Y1  - 2016
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/45535
SN  - 2169-9313
SN  - 2169-9356
VL  - 121
SP  - 1343
EP  - 1364
PB  - American Geophysical Union
CY  - Washington
ER  -