Comparative study of geomagnetic models with different spatio-temporal resolutions and measured data from geomagnetic stations

This study focuses on four INTERMAGNET geomagnetic stations located in the Arctic region and South Atlantic Anomaly regions, where rapid magnetic field changes have been observed in recent years. Utilizing two global geomagnetic field models with different spatial and temporal resolutions, the International Geomagnetic Reference Field (IGRF) model and the Swarm model, a multi-field source model that currently has the highest spatiotemporal resolution in the country, are used to quantitatively investigate the impact of model spatial resolution and updating period on the measured values at geomagnetic observatories. The findings indicate that: (1) For regions without distinct lithospheric magnetic anomalies, the results provided by IGRF and Swarm model are relatively close. However, for regions with more prominent lithospheric magnetic anomalies, the Swarm model with higher spatial resolution provides better agreement with the measurements. (2) In one IGRF updating cycle, there is a significant temporal drift between the geomagnetic station measurements and the IGRF model, with typical drifts up to 100 nT or more, but there were also regional variations in the magnitude of the drift, which was related to the heterogeneity of global variations in the geomagnetic field. In contrast, no significant drift was observed between the geomagnetic station observations and the Swarm model. These results suggest that it is necessary to shorten the updating period of the primary magnetic field during the period of rapid geomagnetic field changes. The statistical results from 120 INTERMAGNET stations around the world also show that, in the five-year update cycle of IGRF, the mean and absolute median differences between the residuals of the Swarm model and the observation results are smaller than those of the IGRF model, and the calculation results of the higher spatial and temporal resolution Swarm model are closer to the observations, which describes the geomagnetic field more accurately. This work can provide the basis and reference for the application of global geomagnetic model.