Not all who wander are lost – updating the International Geomagnetic Reference Field

The Earth’s magnetic field is not static and varies on many different time scales. The main source of the long-term field variation comes from the outer core where the magnetic field is generated by the motion of liquid nickel-iron which in turn ‘drags’ the field lines with it. Thus, the field changes strength and shape slowly over decades. Every five years, IAGA issues an updated version of the magnetic field to capture these slow changes known as secular variation. This series of ‘maps’ or models are known as the International Geomagnetic Reference Field (IGRF) and goes back 125 years. In November 2024, the 14th generation of the model was released, valid from January 1900 to December 2030.

Figure 1: Strength of the magnetic field in microTelsa on the Earth’s surface at 2025.0. Note the low strength region known as the South Atlantic Anomaly.

The magnetic field is represented by a series of numbers known as Gauss coefficients. Using the mathematical technique of spherical harmonic analysis, the magnetic field can be represented continuously in time and space rather than as a 3D grid of cells. This means we can provide a snapshot of the magnetic field above, at or below the Earth’s surface using a very compact set of just 195 numbers, which gives an approximate resolution of 3000 km. This captures the vast majority of the core field and allows us to calculate of Declination angle, Magnetic Dip and Total Field Intensity (see Figure 1) anywhere in the world. We can also track the location of the magnetic poles (see Figure 2).

The first IGRF for 1965 was issued in 1968 when it was difficult to get timely datasets of magnetic measurements from observatories – the data usually took several years to produce and was distributed by post! When the modern internet era began in the 1990s, data could be circulated more rapidly and the IGRF began to be produced in a more timely fashion. Today, we live in a golden era of magnetic field measurement: from hundreds of high-quality geomagnetic observatories to dedicated magnetic missions such as ESA Swarm and Macau Science Satellite. Together these freely available, near-real-time datasets and cheap powerful computer make core field modelling widely accessible.

Figure 2: Estimated location of the geomagnetic and magnetic dip poles from 1900 to 2030. While the north dip pole has accelerated over the past 20 years moving from Canada toward Siberia, the south dip pole has moved much more slowly.

For the 14th generation, 19 teams of geomagnetic scientists from four continents submitted candidate models for the magnetic field in 2020 and 2025 and a forecast of secular variation between 2025 and 2030. In total, there were 47 candidate models to evaluate. The method for combination was determined by a panel of experts using a variety of different technical analyses. The final models were agreed by majority vote and the new coefficients were issued to the official IAGA website on 20th November 2024.

The IGRF is used for research for deep Earth and space weather forecasting, part of many industry applications for correcting surveys (archaeology, oil/gas, mineral exploration) as well as standard pointing and navigation uses. The IGRF truly is an international effort involving thousands of observers, scientists and engineers from around the world. Without their contributions, this would not be possible. We thank them all for their work.

Authors: Ciaran Beggan is senior researcher at British Geological Survey in Edinburgh. This is his fourth venture with the IGRF, starting as a PhD student back in 2009. Clemens Kloss is a postdoctoral researcher at DTU Space in Copenhagen who specialises in improving our view of the Earth’s core magnetic field minus the annoying effects of the aurora.

Space Physics Postdoc Survey

POSTDOCS AND OTHER NON-PERMANENT RESEARCHERS –

Please fill out the survey found at the link below!

https://redcap.helsinki.fi/redcap/surveys/?s=TCPL4WJJCMFAYJDM

Or follow the QR code in this post.

The questionnaire is anonymous and does not require registration.

This survey is intended to measure the working conditions and career prospects of non-permanent researchers in the international heliospheric, magnetospheric, and ionospheric–thermospheric physics communities. We are particularly interested in the challenges faced by post-PhD researchers as they work to advance their careers.

In this project, we are motivated by the following questions:
1. How are postdocs doing in our field?
2. Are there any issues that need to be addressed? What are the causes?
3. What can be done to improve the situation?

We intend to publish the survey results and use them to promote postdoc wellbeing in our community.

The survey will close on January 11, 2025. Be sure to submit your final answers before then, and also to share the link with other postdocs and non-permanent researchers.

For more information, you may contact the survey administrators: konstantinos.horaites@helsinki.fi , giulia.cozzani@cnrs-orleans.fr , eleanna.asvestari@helsinki.fi , maxime.grandin@fmi.fi

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XXth IAGA Workshop Summer School

A summer school for students and young observers was organised as part of the XXth IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing, which recently took place in Vassouras, Brazil. This offered students, young scientists, technicians and young observers from all over the world an opportunity to immerse themselves in the fascinating world of geosciences and deepen their knowledge of the study of the Earth's magnetic field. In this post, we want to share some insights and experiences gathered during this inspiring summer school.

The Summer School at the XXth IAGA Workshop in Vassouras offered 42 participants from many different countries a variety of exciting activities. From lectures by renowned experts in the field of geomagnetic observatory management to practical exercises, poster presentations and demonstrations by instrument manufacturers, the programme was educational and varied.

A highlight was the guided tour through the Geomagnetic Observatory in Vassouras (VSS) where students were given training by experienced colleagues. The participants were able to experience first-hand how magnetic measurements are carried out and learned how this data can be interpreted. These hands-on experiences helped participants to deepen their understanding of the complexity of the Earth's magnetic field and gain new perspectives.

There were also many networking activities, one was an excursion to a Cachasa brewery followed by a get-together with live music and local drinks, where participants were able to socialise with like-minded people and experts. The exchange of ideas and experiences was inspiring and offered participants the opportunity to expand their knowledge and make new connections.

The summer school was not only an opportunity to learn and grow, but also an unforgettable experience that provided participants with new insights, friendships and memories. We would like to thank the Local Organising Committee (LOC), and the Scientific Committee for the rich and inspiring programme and the successful execution of the XX IAGA workshop.

- ICEO (IAGA Interdivisional Commission on Education and Outreach)