MIST
Magnetosphere, Ionosphere and Solar-Terrestrial
Classifying Magnetic Reconnection Regions Using k-Means Clustering: Applications to Energy Partition
By Cara Waters (Imperial College London)
Magnetic reconnection is a universal process which facilitates the repartition of magnetic energy to particle energies. It is important to understand the structure of reconnection regions and how they convert and partition energy. As visual identification of such structures can be subjective and time consuming, we take an unsupervised machine learning approach involving k-means clustering.
Carrying out this clustering on a 2.5-D particle-in-cell simulation of symmetric reconnection comparable to that in Earth’s magnetotail, we identify that the optimal number of clusters is six. We input only field and plasma variables to the clustering, giving a result which is independent of position. We identify two inflow regions, two outflow regions, and two pairs of separatrices. By looking at the distributions of the energy flux densities in these regions, we confirm that outgoing particle energy flux densities from reconnection decrease as guide field increases. The ion enthalpy flux density is the most dominant form of energy flux density in the outflows, agreeing with previous studies, and Poynting flux density may be dominant at some points in the outflows and is only half that of the Poynting flux density in the separatrices. This demonstrates an approach which may be applied to large volumes of data to determine statistically different regions within phenomena in simulations and could be extended to in situ observations, applicable to future multi-point missions.
Results of carrying out k-means clustering with six clusters on comparable simulation runs with (a) BG = 0, (b) BG = 0.1, and (c) BG = 0.2. Magnetic field lines are shown in black, with the colour showing the regions identified by the k-means clustering. These regions are labelled in relation to the equivalent directions in GSM coordinates in the case of magnetotail reconnection. Each simulation run has k-means carried out independently with variables scaled in the same manner and subsequent clusters re-numbered for comparison between each case.
See publication for details:
Cara L. Waters, Jonathan P. Eastwood, Naïs Fargette, David L. Newman, Martin V. Goldman. Classifying Magnetic Reconnection Regions Using k-Means Clustering: Applications to Energy Partition, JGR: Space Physics, 2024, 129, 10. https://doi.org/10.1029/2024JA033010
Release of the 14th Generation of the IGRF
By Ciaran Beggan (British Geological Survey)
The standard reference model for the Earth’s main magnetic field is known as the International Geomagnetic Reference Field (IGRF). Its primary purpose is to aid scientific research as well as general navigation.
The Earth’s main magnetic field is not static and it changes slowly over time as a result of the chaotic and unpredictable flow of liquid nickel-iron in the outer core. To account for the change (known as secular variation), the geomagnetic community produces an updated version of the IGRF every five years. The latest IGRF is the 14th update and was released in November 2024 to ensure the continuation from the 13th generation whose validity ended in January 2025.
The model consists of a series of snapshot Gauss coefficients every five years from 1900 to 2030. Gauss coefficients can be thought of as the weights assigned to spherical harmonic functions, the summation of which allows a compact and efficient method of determining the magnetic field anywhere on the globe, above or below the surface. The coefficients are defined to degree and order 13 in the latest generation, which gives an approximate spatial resolution of 3000km at the surface.
Analysis shows that the Earth’s magnetic field continues to drift westwards across most the globe and weaken. The South Atlantic Anomaly which has deepened by around 150 nanoTesla over five years and moved westward at around 20km/year. A second low point offshore of South Africa is forming. The magnetic dip pole in the northern hemisphere continues to move rapidly away from Canada toward Siberia at a rate of 35km/year. In contrast, the southern hemisphere pole velocity has remained below 10km/yr since the 1960s. Interestingly, in early to mid-2026, both poles should briefly have the same longitude (136°E).
Maps of the three components of the magnetic field at 2025. The panels illustrate the Declination angle (i.e. angle between true and magnetic North), the Inclination (or magnetic dip) and Total Field Intensity from IGRF-14.
Announcement of New MIST Councillors.
We are very pleased to announce the following members of the community have been elected unopposed to MIST Council:
- Rosie Johnson (Aberystwyth University), MIST Councillor
- Matthew Brown (University of Birmingham), MIST Councillor
- Chiara Lazzeri (MSSL, UCL), Student Representative
Rosie, Matthew, and Chiara will begin their terms in July. This will coincide with Jasmine Kaur Sandhu, Beatriz Sanchez-Cano, and Sophie Maguire outgoing as Councillors.
The current composition of Council can be found on our website, and this will be amended in July to reflect this announcement (https://www.mist.ac.uk/community/mist-council).