# Spatial and Temporal Separation of Ocean Tide Induced Magnetic Fields

The induced magnetic signal due to conductive ocean water moving through the Earth's main magnetic field has gained some significant interest in recent years. In Tyler et al. (Science 299, 2003), the signal of the oceanic M2 tide (12.42h periodicity) has for the first time been extracted from CHAMP magnetic field data. In Sabaka et al. (Geophys. J. Int. 200, 2015) the M2 tidal signal has been included for the first time in a comprehensive magnetic field model, namely, the CM5 model (cf. Figure 1, left). Due to its comparatively small strength in relation to other contributions like the core, the ionospheric, and the crustal field, the ocean tide induced magnetic field is fairly difficult to extract from overall (satellite) magnetic field measurements. Yet, improved models of the ocean tidal magnetic field could help to improve conductivity models of the Earth as well as monitor global-scale ocean currents themselves.

The goal of this project is twofold: (1) Using wavelets to investigate the temporal behaviour of the ocean induced magnetic signal in more detail, in particular, investigating the leakage of power into periodicities adjacent to the M2 periodicity and possibly obtaining information on weaker tidal modes than M2. (2) Taking into account the spatial origin of the ocean induced magnetic signal, in particular, designing a set of basis functions that satisfy the magnetic induction equation and whose support at the Earth's surface is concentrated inside the oceans. After the mathematical modeling and construction has been done, the method should be applied to (Swarm) satellite magnetic field data. The aspect of including spatial structures for the separation of ocean tide magnetic signals from the overall geomagnetic field has not been regarded in previous attempts.

# Project Information

DFG project GE 2781/1-1 : Time-Space Multiscale Separation of Ocean Tide Generated Magnetic Fields (PI: Christian Gerhards, Martin Rother)