Earth’s magnetic field is vital for life on our planet. Generated deep within the outer core by the churning of molten iron, this invisible force shields us from harmful cosmic radiation and provides a navigational compass for species ranging from birds to sea turtles. But the geomagnetic field is far from static or uniform – it constantly changes in strength and direction across the globe and over time. Studying and mapping these complex variations is crucial to understand Earth’s deep interior and for practical applications like navigation and surveying.
The World Magnetic Model (WMM) is the standard model used for mapping the geomagnetic field and its fluctuations. Produced collaboratively by the US National Oceanic and Atmospheric Administration (NOAA) and British Geological Survey (BGS), it is relied upon worldwide by military, civilian and commercial entities. The WMM provides a mathematical representation of the field which is regularly updated with new data from satellite missions, ground stations and other sources. However, modeling the intricacies of the geomagnetic field requires measurements of the highest precision and global coverage – a need fulfilled by the European Space Agency’s (ESA) Swarm constellation.
Swarm and the Geomagnetic Field
The Swarm mission was launched by ESA in 2013 to study and precisely map variations in Earth’s magnetic field over space and time. The constellation consists of three identical satellites. Swarm provides multi-point measurements of the magnetic signals from the magnetosphere, ionosphere, lithosphere and the core. Combining data from the three satellites and their different polar orbits provides greater temporal resolution and separation of external and internal field sources.
The key objectives of the Swarm mission are:
- Improving our understanding of core dynamics and the geodynamo process that sustains the magnetic field
- Mapping lithospheric magnetization patterns and radiation belts
- Monitoring geomagnetic changes leading to improved models at various scales
- Investigating the interaction between the magnetosphere and solar wind
- Studying electric currents in the ionosphere and magnetosphere
To achieve these science goals, each Swarm satellite carries precision magnetometers, an electric field instrument, GPS receivers, laser retroreflector and accelerometer. Together, these instruments provide high-resolution scalar and vector measurements of magnetic fields, along with positioning and attitude data.
Contributions to the World Magnetic Model
As a pioneering magnetic mapping mission, the data collected by Swarm has been vital for improving geomagnetic field models, especially the WMM. Some of its key contributions are:
- High-accuracy vector and scalar magnetic data: The absolute magnetometer and vector field magnetometer on Swarm have provided high-precision readings of the strength and direction of magnetic fields along each satellite’s orbit. This accuracy is far greater than previous magnetic field missions.
- Global coverage: Swarm’s three satellites have polar, near-polar orbits sweeping different local times, providing complete latitudinal coverage spanning the core, crust, ionosphere and magnetosphere. The constellation observes the same region at slightly different times, helping distinguish temporal variations in the field.
- Separation of internal and external fields: The multi-satellite formation enables better separation between the external magnetic signals from space weather and internal fields generated in the core and lithosphere. This allows modeling each source more accurately.
- Frequent data updates: New data from Swarm is provided at least once per month to geomagnetic modelers, enabling continuous incorporation of measurements in near real-time rather than waiting for an entire mapping mission to end.
- Open access data policy: Swarm data is freely available for use by the scientific community and organizations like NOAA and BGS for geomagnetic field modeling.
By combining Swarm’s precision data on rapid timescales with ground observatories and existing field models, scientists have been able to track geomagnetic variations with unprecedented clarity. The result has been substantial improvements in global models like the WMM.
Enhancing Global Magnetic Maps
The WMM provides critical parameters for navigation, orientation and geomagnetic applications across the world. It is represented mathematically using formulas that best fit available field data globally.
Swarm’s unique design and precision instrumentation has led to significant enhancement of the WMM’s accuracy and spatial resolution. The enhanced measurements better capture small-scale fields and short-term chaotic fluctuations, improving global declination, inclination and intensity maps.
The latest WMM released in 2020 incorporated Swarm data extensively. Scientists expect further refinement with the 2025 edition as Swarm continues providing new insights into the intricacies of Earth’s magnetic field.
Understanding Our Magnetic Planet
The World Magnetic Model is the product of international collaboration, relying on open data access and coordination between space agencies, research institutions and national mapping agencies. As one of ESA’s pioneering “Explorer Missions”, Swarm demonstrates the immense value of precisely mapping physical fields for both scientific discovery and practical applications. Its novel mini-satellite constellation concept has delivered an unprecedented dataset to unravel the complex dynamics of the geomagnetic field.
Swarm’s high-resolution view of Earth’s magnetic fluctuations across space and time will help refine models of core convection and composition. It will improve understanding of ionospheric currents and their impact on communication systems and power grids. The mission provides broader insights into planetary magnetism and the role of magnetic shielding for habitability. As new data continues streaming in, Swarm stands poised to reveal further secrets of our restless magnetic field, a phenomenon so central to life on Earth and the technology we depend upon.
