Demonstrate reliable extraction of long-period ocean-induced magnetic signals from real satellite observations

Demonstrate, using real low-Earth-orbit satellite magnetic field observations, that long-period (months to years) Ocean-Induced Magnetic Field (OIMF) signals generated by motional induction of the ocean general circulation can be reliably extracted from the data.

Background

The paper reviews the expected space–time characteristics of the Ocean-Induced Magnetic Field (OIMF) and compares them with other geomagnetic sources at satellite altitude. While tidal OIMF signals have been successfully retrieved from satellite data, detection of the general circulation component has only been claimed once and has not been independently reproduced. The authors’ simulations indicate that the OIMF can dominate the core field at sufficiently high spherical harmonic degrees and shorter periods, and synthetic inversions suggest retrieval is possible under idealized conditions.

However, in real observations, ionospheric and magnetospheric (and their Earth-induced) fields are significantly larger than the OIMF in relevant period bands, posing a major challenge. The authors therefore emphasize that, despite promising modelling and synthetic tests, a validated demonstration using real satellite measurements remains outstanding.