A global mantle conductivity model derived from 8 years of Swarm satellite magnetic data

Mantle conductivity imaging is one of the scientific goals of the forthcoming Macau Science Satellite-1 (MSS-1). To achieve this goal, we develop a data analysis and inversion scheme for satellite magnetic data to probe global one-dimensional (1D) mantle conductivity structures. Using this scheme,we present a new global mantle conductivity model by analyzing over 8 years of Swarm satellite magnetic data. First, after sophisticated data selection procedures and the removal of core and crustal fields, the inducing and induced spherical harmonic coefficients of magnetic potential due to the magnetospheric ring current are derived. Second, satellite C-responses are estimated from the time series of these coefficients. Finally, the observed responses are inverted for both smooth and three-jump conductivity models using a quasi-Newton algorithm. The obtained conductivity models are in general agreement with previous global mantle conductivity models. A comparison of our conductivity model with the laboratory conductivity model suggests the mean state of the upper mantle and transition zone is relatively dry. This scheme can be used to process the forthcoming Macau Science Satellite-1 magnetic data.