Tracking geomagnetic impulses at the core–mantle boundary

The main magnetic field of the Earth is generated and maintained by convective motions in the fluid outer core. Temporal field variations occur on an impressive variety of scales, ranging from months to millions of years. Among these, the most intriguing features are geomagnetic “impulses” or “jerks” [V. Courtillot, J. Ducruix and J.L. Le Mouël, Sur une accélération récente de la variation séculaire du champ magnétique terrestre, Acad. Sci. Paris C.R., D287, (1978) 1095–1098., J.L. Le Mouël, J. Ducruix and C. Ha Duyen, Geophys. Res. Lett., 5, (1983) 369. [1,2]]. Here, we investigate these very rapid events at the surface of the Earthʹs core using a global model, designed for use at this depth. We identify two regions of very active variations, where wave-like structures propagate. The geometrical characteristics of these wave-like motions provide new constraints on the intricate dynamics of the core.