Extracting waves from noisy geomagnetic data – A synthetic study of equatorially trapped waves in Earth's core

Geomagnetic Secular Variation (SV) and acceleration (SA) can provide a wealth of information about fluid motions in the core. However, recovering this information from noisy data is complicated by the structure of the magnetic field at the core-mantle boundary. We demonstrate the challenge using a numerical model for equatorial waves to produce synthetic records of SV and SA. We show that interpreting magnetic oscillations directly as waves in Earth's core can lead to spurious conclusions due to coupling between non-dipole components of the magnetic field and wave structures. Using the structure of our modeled waves, we derive a set of methods to detect waves using magnetic field observations. We show that these methods can recover the wave period, longitudinal wavenumber, equatorial symmetry, latitudinal extent, and amplitude for synthetic equatorial waves in Earth's core when the wave fluid velocity is ∼0.5 km/yr or greater