2020/11/12 by Kyle Gwirtz, Matthias Morzfeld, Alexandre Fournier +1 · 8 citations
Biochemistry, Genetics and Molecular Biology · Earth and Planetary Sciences · Mathematics · Physics and Astronomy · #Classical mechanics #Computational physics #Computer science #Dipole #Dynamo #Dynamo theory #Excursion #Geological formations and processes #Geology #Geology and Paleoclimatology Research #Geomagnetic reversal #Geomagnetism and Paleomagnetism Studies #Geometry #Geophysics #Hierarchy #Intensity (physics) #Magnetic dipole #Magnetic field #Mathematics #Moment (physics) #Optics #Physics #Quantum mechanics #Scalar (mathematics) #Statistical physics #physics.geo-ph
paper · pdf · doi:10.1093/gji/ggaa542
published in Geophysical Journal International 225(1), 277-297 (Oxford University Press)
openalex publication_date 2020/11/12 · arxiv created 2020/12/23 · arxiv updated 2020/12/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
SUMMARY We study predictions of reversals of Earth’s axial magnetic dipole field that are based solely on the dipole’s intensity. The prediction strategy is, roughly, that once the dipole intensity drops below a threshold, then the field will continue to decrease and a reversal (or a major excursion) will occur. We first present a rigorous definition of an intensity threshold-based prediction strategy and then describe a mathematical and numerical framework to investigate its validity and robustness in view of the data being limited. We apply threshold-based predictions to a hierarchy of numerical models, ranging from simple scalar models to 3-D geodynamos. We find that the skill of threshold-based predictions varies across the model hierarchy. The differences in skill can be explained by differences in how reversals occur: if the field decreases towards a reversal slowly (in a sense made precise in this paper), the skill is high, and if the field decreases quickly, the skill is low. Such a property could be used as an additional criterion to identify which models qualify as Earth-like. Applying threshold-based predictions to Virtual Axial Dipole Moment palaeomagnetic reconstructions (PADM2M and Sint-2000) covering the last two million years, reveals a moderate skill of threshold-based predictions for Earth’s dynamo. Besides all of their limitations, threshold-based predictions suggests that no reversal is to be expected within the next 10 kyr. Most importantly, however, we show that considering an intensity threshold for identifying upcoming reversals is intrinsically limited by the dynamic behaviour of Earth’s magnetic field.