Magnetic Fields Induced in the Solid Earth and Oceans

Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic field. Oceans play a special role in the induction, due to their relatively high conductance of large lateral variability. Electric currents that generate secondary magnetic fields are induced in the oceans by two different sources: by time varying external magnetic fields, and by motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in the accurate and detailed prediction of magnetic fields induced by these sources has been achieved during the last years, utilizing realistic 3-D conductivity models of the oceans, crust and mantle. In addition to these improvements in the prediction of 3-D induction effects, much attention has been paid to identifying magnetic signals of oceanic origin in observatory and satellite data. During the talk we will present the results of 3-D model studies that aim at estimating magnetic signals (at ground and satellite altitude) induced by a variety of realistic sources. In particular we will consider induction from ionospheric currents (Sq and electrojets), magnetospheric currents (magnetic storms), ocean tides, and global ocean circulation. Finally, we will discuss how the results of 3-D predictions can be utilized in geomagnetic field modeling and in a recovery of deep conductivity structures.