Day 4

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Paper title Signatures of the global ocean circulation in geomagnetic secular variation and acceleration
  1. Christopher Finlay DTU Space Speaker
  2. Jakub Velímský Charles University, Faculty of Mathematics and Physics
  3. Clemens Kloss DTU Space - Technical University of Denmark
Form of presentation Poster
  • B2. Earth Explorer missions
    • B2.05 Swarm - ESA's Extremely Versatile Magnetic Field and Geospace Explorer
Abstract text Changes in the global ocean circulation driven by winds and density gradients produce, via motional induction, time-varying geomagnetic signals. On long length and time scales these signals are hidden beneath larger core-generated signals but, due to their location at Earth's surface, on sufficiently short length scales and considering month to interannual timescales they may in principle be detectable. Such signals would provide useful information related to ocean circulation and conductivity variations. We explore the prospects for retrieving these signals using forward simulations of the magnetic signals generated by an established ocean circulation model (the ECCO model v4r4), realistic ocean, sediment, lithosphere and mantle electrical conductivities and the ElmgTD time-domain numerical scheme for solving the magnetic induction equation, including both poloidal and toroidal parts.  We show that considering 4-monthly averaged signals the oceanic magnetic secular acceleration beyond spherical harmonic degree 10 may reach detectable levels.  The impact of realistic data processing and time-dependent field modelling strategies on the retrieved synthetic ocean signal will be described. Progress on synthetic tests including both core and oceanic sources will be reported. The benefit of improved temporal coverage by future geomagnetic missions, particularly the proposed NanoMagSat mission, together with the importance of suitable representations of the oceanic signal, will be described.