Electrical conductivity of the Earth's mantle from the first Swarm magnetic field measurements

Research areas:
Geophys. Res. Lett.
We present a 1-D electrical conductivity profile of the
Earth's mantle down to 2000 km derived
from L1b Swarm satellite magnetic field measurements from November 2013 to September 2014. We first
derive a model for the main magnetic field, correct the data for a lithospheric field model, and additionally
select the data to reduce the contributions of the ionospheric field. We then model the primary and induced
magnetospheric fields for periods between 2 and 256 days and perform a Bayesian inversion to obtain the
probability density function for the electrical conductivity as function of depth. The conductivity increases
by 3 orders of magnitude in the 400~900 km depth range. Assuming a pyrolitic mantle composition, this
profile is interpreted in terms of temperature variations leading to a temperature gradient in the lower
mantle that is close to adiabatic.