Models and predictions of Earth’s magnetic field based on geomagnetic observatory data

Abstract Observations of the geomagnetic field taken at Earth’s surface are processed to construct a set of continuous models of the geomagnetic field and its secular variation from 1956 to 2033. One of these models, the parent model, provides candidate main field models for the epochs 2020 and 2025 to the 14th generation of the International Geomagnetic Reference Field (IGRF). The secular variation candidate model for the period 2025–2030 is derived from a forecast of the secular variation in 2027.5, which results from a multi-variate singular spectrum analysis of the secular variation from 1960 to 2023. Apart from the parent model, we also derive models to higher spherical harmonic degrees than $$\ell =14$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ℓ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> </mml:math> to study small-scale features of the core field and its temporal variation. A comparison with a satellite-based field model indicates a good agreement for the core field, but shows significant differences for the secular variation, which probably could be explained by the different source geometry of the data. Our results suggest a strengthening of the meridional core flow in recent years and the existence of north–south oriented undulations in the radial component of the secular variation which may be related to the presence of waves in Earth’s liquid outer core. Graphical Abstract