Team Leaders: Joel Allred, NASA/GSFC, USA, and Malcolm Druett, University of Sheffield, UK

Session: 2–6 March 2026

Abstract: Understanding solar eruptions such as flares, jets, and coronal mass ejections is a central goal of space physics. New observations and advances in theory and computing now allow increasingly realistic modelling of flare processes, from global magnetic field evolution to particle acceleration and transport across vast spatial scales. While no single model captures the full multiscale complexity, several state-of-the-art codes describe complementary aspects of flare evolution. The Team systematically compares and validates leading flare models, including MPI AMRVAC, MURaM, Bifrost, and RADYN plus FP, using multi wavelength observations to test their predictions. By identifying key physical processes and methodological gaps, we aim to guide the development of next generation end-to-end flare models and strengthen the interpretation of new solar observations.

Team Leader: Juan Antonio Añel, Universidade de Vigo, Spain

Session: 14–18 September 2026

Abstract: The mounting evidence of climate change’s impacts on the middle and upper atmosphere highlights the urgent need for observational data to monitor and understand these trends. In this regard, numerous critical scientific questions remain unanswered, emphasising the necessity for additional research and international cooperation in this area. Current challenges in satellite monitoring of the middle and upper atmosphere over the next decade are concerning, particularly owing to limited data series available for these layers. To address these issues, the goals of the Team are to advance the study of climate change in the middle and upper atmosphere, enhance data availability, and devise strategies for evaluating and monitoring climate change through satellite observations. The Team comprises a diverse group of international experts covering diverse atmospheric layers, including the stratosphere, thermosphere, and ionosphere, as well as aspects of space debris and Earth observation.

Team Leaders: Karl Battams and Matthew Knight, United States Naval Academy, USA

Session: To be scheduled

Abstract: The Geminid meteor shower is one of the most intense annual showers, yet its origin remains puzzling. Unlike most showers linked to comets, its parent body, asteroid (3200) Phaethon, appears asteroidal in nature, raising questions about how the Phaethon–Geminid system formed and evolved. Recent heliophysics spacecraft observations have revealed new details of Phaethon’s activity, including the first white-light detections of the Geminid stream core. Together with the upcoming JAXA DESTINY+ mission encounter in the early 2030s, these discoveries make a comprehensive reassessment timely. The Team gathers experts in heliophysics imaging, small bodies, meteoroid streams, and dust properties to synthesise recent advances, redefine key questions, and produce an authoritative, up to date study of the Phaethon–Geminid system.

Team Leaders: Yulia Bogdanova, STFC Rutherford Appleton Laboratory, UK, and Simon Wing, Johns Hopkins University Applied Physics Laboratory, USA

Session: 23–27 March 2026

Abstract: Earth’s magnetospheric cusps are key entry points for solar wind plasma through magnetic reconnection, controlling energy and plasma transfer into the magnetosphere and ionosphere. Despite extensive study, important questions remain about their multiscale structure and variability. This project brings together experts in data analysis and modeling to investigate small- and medium-scale plasma fluctuations, longitudinal variability linked to reconnection geometry, and the impact of asymmetries in the magnetosheath and magnetosphere on energy transport. The Team uses coordinated observations from Cluster, THEMIS or MMS, and low-altitude missions such as DMSP and Swarm. The results will improve understanding of solar wind magnetosphere ionosphere coupling and help define science priorities for future missions including TRACERS, SMILE, and Bepi Colombo.

Team Leaders: Martina Bramberger, NCAR, USA, and Corwin Wright, University of Bath, UK

Session: 11–15 May 2026

Abstract: For the last twenty years we have been able to monitor stratospheric dynamics in extraordinary detail, facilitated by an effective and comprehensive high-resolution global satellite measurement network. However, this network is aging and will likely be entirely gone by the late 2020s, with no current plans to replace it. This is a major problem for the continuing development of weather and climate models, an increasingly large fraction of which incorporate a resolved high-resolution stratosphere. While missions are currently under consideration by both NASA and ESA to fill this gap, they are yet to be approved and even if selected would not launch until the mid-2030s. In WAVE-GAP, the Team identifies and comprehensively assess a range of approaches to filling this data gap, including the use of lower-resolution satellites, ground-based and in-situ observations, dynamical modelling and ML/AI approaches. The researchers focus on the specific case of small-scale atmospheric gravity waves playing a key role in atmospheric dynamics, using these as a test bed to develop robust and adaptable solutions to the lack of observations. Building on this example, the Team further aims to produce broad recommendations which will be transferable to other atmospheric dynamical and chemical variables affected by the gap.

Team Leader: Jeremy Dargent, École Polytechnique, France

Session: 23–27 February 2026

Abstract: The Team investigates how ionospheric plasma is energised as it travels through the magnetosphere. Magnetospheric plasma originates from both the solar wind and the ionosphere, but ionospheric plasma starts at much lower energies and is often below instrument detection thresholds despite its significant density. To understand its global evolution, the Team members combine large scale magnetohydrodynamic simulations with local kinetic studies and spacecraft observations. Global models will identify regions where significant heating is expected, while kinetic simulations and measurements will characterise the responsible processes. Our goal is to provide, for each major ionospheric plasma source, a comprehensive description of its transport and energisation throughout the magnetosphere.

Team Leaders: Mark Gieles, ICREA & University of Barcelona, Spain, and Paolo Padoan, Dartmouth College & University of Barcelona, USA

Session: 13–17 April 2026

Abstract: Globular clusters (GCs) are dense stellar systems, with ages comparable to the age of the Universe, which are found in nearly all galaxies. Thanks to the revolutionary observations of the Hubble Space Telescope (HST) and follow-up spectroscopy from the ground, we discovered that most stars in GCs have anomalous abundances, in the form of increased helium abundances and variations in other light elements. These abundances are telltales of hydrogen burning at temperatures well in excess of the central temperatures of the stars themselves. All old GCs display these “multiple populations” (MPs), but they have remained elusive in young massive clusters and their origin is shrouded in mystery. A long-standing question that this proposal aims to address is: “What is the origin of these anomalous light-element abundances?” The Team investigates the scenario in which extremely massive stars (~103 solar masses) – that may have existed in GCs in the early Universe – polluted GCs during their formation. The novelty lies in the combination of hitherto disconnected approaches, using space- and ground-based observations, stellar evolution and nucleosynthesis calculations and direct modelling of GC formation. This project sheds light on the formation of GCs at high redshift and provide insights into fundamental problems in astrophysics, such as the stellar initial mass function (IMF) and star and galaxy formation at high redshift. Solving this problem now is timely given our ability to directly observe GC formation in the earliest phases of galaxy formation with the James Webb Space Telescope (JWST).

eam Leaders: Laurent Gizon, Max Planck Institute for Solar System Research, Germany, and Rhita-Maria Ouazzani, Observatoire de Paris, France

Session: 5–9 October 2026

Abstract: Recent advances in solar and stellar physics reveal that inertial modes, global oscillations driven by the Coriolis force, provide powerful probes of internal structure and rotation. In the Sun, long time series have identified rich spectra of inertial modes, including high latitude modes that help maintain the observed pole to equator temperature contrast. In intermediate mass stars, gravito-inertial and Rossby modes detected by Kepler constrain core rotation, stratification, and magnetic activity, while broader stellar samples show characteristic features linked to unresolved modes. These results establish inertial modes as key diagnostics of stellar interiors and convection. However, research in the solar and stellar communities has largely progressed separately. The Team unites experts from both fields to exchange methods, develop joint analyses, and advance a unified understanding of inertial modes across stars.

Team Leaders: Kseniia Golubenko, University of Oulu, Finland, and Hella Wittmann, GFZ Potsdam, Germany

Session: 26–30 January 2026

Abstract: Beryllium-10 is produced by cosmic rays in the atmosphere and preserved in ice cores, sediments, and soils, making it a key proxy for past solar activity, cosmic ray flux, geomagnetic changes, and extreme solar events. However, interpreting Beryllium-10 records is challenging because atmospheric transport, stratospheric circulation, and climate variability also influence its deposition, introducing uncertainties in reconstructions of solar cycles and extreme solar energetic particle events. The Team combines expertise in solar physics, atmospheric science, and isotope geochemistry to refine Beryllium-10 as a quantitative solar proxy. By integrating high resolution records with advanced atmospheric transport models, we will reassess known extreme events such as those in 774 CE and 993 CE and search for previously unidentified events. The project aims to improve reconstructions of past solar variability and better constrain the risks of future extreme solar activity.

Team Leader: Mario Guarcello, INAF, Italy

Session: 9–13 March 2026

Abstract: Star formation occurs in a wide variety of environments. The understanding of star formation in the solar neighbourhood is biased toward low-mass star-forming regions (typically hosting a few hundred to a few thousand members) with solar metallicity (i.e., an abundance of chemical elements heavier than hydrogen and helium similar to that of the Sun). This is unfortunate, as a significant fraction of stars form in massive star-forming regions, which host rich populations of massive stars. These stars regulate the formation of low-mass stars and their planets through their intense high-energy radiation and stellar winds. As a result, the outcomes of the star formation process and the early stellar evolution in massive environments can differ from those in low-mass regions. Additionally, the metallicity of the star-forming region is expected to play a crucial role. Exploring star formation at low metallicity is particularly important, as it provides insights into the products of star formation in the early epochs of cosmic evolution when metallicity was low and star formation was especially intense. The project aims to fully exploit the capabilities of the James Webb Space Telescope to determine the efficiency of very low-mass star formation and their early evolution in the most massive young stellar clusters in the Milky Way, as well as in low-metallicity environments in the Magellanic Clouds. The exceptional performance of JWST is essential, as both massive and low-metallicity star-forming environments are located at large distances from us and are typically affected by significant interstellar extinction (especially the former).

Team Leaders: Miroslav Hanzelka, GFZ Helmholtz Centre for Geosciences, Germany, and Oliver Allanson, University of Birmingham, UK

Session: 3–7 November 2025

Abstract: Advances in plasma theory during the 1950s and 1960s led to the development of comprehensive models of Earth’s radiation belts capable of describing and forecasting many observational phenomena. These early models, developed with sparse and technically limited wave and particle measurements, were based on quasi-linear theory, treating particle transport as purely diffusive. However, recent high-fidelity spacecraft data (collected by Cluster, THEMIS, Van Allen Probes, Arase, MMS, SAMPEX, POES, GPS, CubeSat missions, and others) have repeatedly challenged this modelling approach, revealing discrepancies that highlight the need to incorporate non-diffusive irreversible processes that take place on small timescales. Addressing these gaps requires tackling fundamental questions on nonlinear particle acceleration, transport, and loss. These advancements are critical not only for improving model accuracy but also for addressing societally important challenges, including forecasting radiation hazards in the near-Earth space environment and understanding the impact of energetic particle loss on the atmosphere. This project brings together a diverse team of leading international experts to: (i) unify current knowledge of relativistic particle dynamics in the radiation belts; (ii) investigate key processes beyond classical diffusion, such as radial advection and nonlinear wave-driven acceleration; and (iii) provide recommendations for future spacecraft missions to enable critical breakthroughs in radiation belt research.

Team Leaders: Laura Hayes, Dublin Institute for Advanced Studies, Ireland, and Hannah Collier, FHNW, Switzerland

Session: 20–24 April 2026

Abstract: Solar Orbiter’s Major Flare Solar Orbiter Observing Plan (SOOP) campaign has provided unprecedented datasets to investigate how solar flares release energy, accelerate particles, and heat plasma in the solar atmosphere. Successfully conducted in 2024, capturing over 22 flares, and with another campaign planned for 2025, these observations captured high-cadence, high-resolution flare data resolving rapid plasma evolution on fine spatial and temporal scales. The campaign leveraged extreme ultraviolet (EUV) imaging from the High-Resolution Imager (HRIEUV) on the Extreme-Ultraviolet Imager, which operated in short-exposure mode to provide 2-second-cadence, non-saturated EUV flare observations, offering an unparalleled view of flare ribbons and loop dynamics. Simultaneously, hard X-ray imaging spectroscopy from STIX provided continuous measurements of flare energy release and particle acceleration, enabling a multi-wavelength investigation of energy transport and reconnection processes. Additionally, SPICE captured spectroscopic flare plasma observations at multiple temperatures in selected events, further constraining energy deposition and the atmospheric response. This Team brings together an international group of experts to fully exploit these datasets, with three key aims:
(1) develop optimised data analysis techniques and create community resources, including catalogues, pre-processed datasets, and documentation;
(2) analyse high-cadence Solar Orbiter observations of flare ribbons and loop dynamics to investigate energy transport;
(3) and refine observing strategies for future Solar Orbiter campaigns and next-generation missions like MUSE and Solar-C.

By combining observational data-driven analysis and strategic planning, this team will maximise the scientific return of Solar Orbiter’s major flare campaigns, and address fundamental questions about how flares release energy, accelerate particles, and heat plasma in the solar atmosphere.

Team Leader: Daniel Hestroffer, Observatoire de Paris, France

Session: 16–20 February 2026

Abstract: Small bodies beyond Neptune – from Trans-Neptunian Objects to the Oort cloud – trace the formation and dynamical evolution of the outer Solar System. Their orbits reflect the combined influence of giant planets, stellar encounters, and the Galactic potential as the Solar System moves through the Milky Way. The Team aims to quantify how this stellar and galactic environment has shaped the Outermost Solar System over 4.5 Gyr. By combining new observational constraints (including Gaia and forthcoming Rubin/LSST surveys) with dedicated N-body simulations, we will model the long-term evolution of distant small bodies and compare predictions with observed orbital distributions. This interdisciplinary effort will provide new constraints on the Solar System’s birth environment and on the formation and structure of the Oort cloud.

Team Leaders: Allison Jaynes, University of Iowa, USA, and Lynn Harvey, LASP University of Colorado, USA

 Session: 23–27 March 2026

Abstract: Energetic auroral precipitation, particularly from pulsating aurora, produces nitric oxides (NOx) in the mesosphere and lower thermosphere. During polar night, NOx can descend into the stratosphere – enhanced by the polar vortex and modulated by planetary waves – where it catalytically destroys ozone, sometimes causing months-long depletion after a single strong event. However, the overlap between regional auroral NOx sources, planetary wave structure, and vortex dynamics remains poorly quantified. Current models underestimate NOx production and transport, although high-resolution WACCM-X simulations show that resolved gravity waves significantly enhance descent. Coarse-resolution models still miss this effect, limiting our understanding of Sun–Earth coupling. The project aims to determine how the atmospheric state controls the impact of energetic electron precipitation on ozone and middle-atmosphere chemistry.

Team Leaders: Larry Kepko, NASA, USA, and Sara Gasparini, University of Bergen, Norway

Session: 2–6 February 2026

Abstract: Earth’s magnetosphere couples to the ionosphere through field-aligned currents (FACs) and particle precipitation, shaping ionospheric conductivity and dynamics. While large-scale current systems are well known, mesoscale structures (tens to hundreds of kilometres, minutes in duration) remain poorly understood owing to observational limitations. The new EZIE mission will provide 2D maps of ionospheric currents, revealing the temporal evolution of mesoscale systems, but lacks in-situ measurements. Conversely, Swarm delivers precise FAC and convection data without the broader context of imaging. Combined with new high-resolution ground-based datasets (e.g., SuperDARN, TREx) and data-assimilation tools such as Lompe, there is now an unprecedented opportunity to resolve mesoscale auroral electrodynamics. The Team integrates space- and ground-based observations to advance understanding of mesoscale magnetosphere–ionosphere coupling.

Team Leaders: Amir Khan and Paolo Sossi, ETH Zurich, Switzerland

Session: 23–27 February 2026

Abstract: The structure and composition of planetary crusts, mantles, and cores provide key insights into their thermal state, chemistry, origin, and evolution. Recent advances, including improved seismic models suggesting a denser Earth outer core, machine-learning approaches to interior properties, and more precise laboratory measurements, offer new opportunities to refine models of terrestrial planet interiors, from Earth and Mars to the Moon and Vesta. The Team combines seismology, geophysics, mineral physics, and geo- and cosmochemistry to better constrain the structure and formation of rocky planets. Using data from ground- and space-based missions (e.g., LAGEOS, InSight, Apollo), the results will also support upcoming missions such as BepiColombo and the lunar Farside Seismic Suite, with implications extending to exoplanetary systems.

Team Leader: Solene Lejosne, University of California Berkeley, USA

Session: 16–20 March 2026

Abstract: Drift phase structures appear as organised peaks and valleys in radiation belt spectrograms and are now recognised as a common feature of planetary radiation belts. Although they are generally linked to radial transport, their origin remains debated. They may result from impulsive electric field perturbations, producing drift echoes, or from drift resonance with ultra-low-frequency waves. The relative importance and efficiency of these mechanisms are still unclear, as is their overall impact on global radiation belt dynamics. This project combines satellite observations with theoretical and numerical modelling to determine the dominant generation processes of drift phase structures. The researchers also quantify their role in radiation belt acceleration and validate model results against observations to improve current radiation belt paradigms.

Team Leaders: Zhaosheng Li, Xiangtan University, China, and Duncan Galloway, Monash University, Australia

Session: To be scheduled

Abstract: Thermonuclear X-ray bursts result from unstable nuclear burning of material accreted onto a neutron star from a companion via Roche lobe overflow. Renewed interest in these events is driven by new multi wavelength observations, discoveries of previously unknown burst behaviour, and data from recent missions such as NICER, Insight-HXMT, and NinjaSat. Different burning regimes produce short bursts, intermediate-duration bursts, and superbursts. Studying these events probes nuclear reaction physics and constrains neutron star masses, radii, and the equation of state. This project integrates multi wavelength observations, laboratory experiments, and numerical simulations to understand burst mechanisms, burst disk interactions, and their connection to jet production.

Team Leaders: Manuela Lippi, INAF, Italy, and Geronimo Villanueva, NASA Goddard Space Flight Center, USA

Session: 9–13 February 2026

Abstract: The relative abundance of nuclear spin configurations in multi-hydrogenated molecules such as H2O, H2, H2CO, and NH3 depends on formation temperature. Because spin states cannot easily change after formation, spin ratios have long been used as cosmogonic thermometers to infer formation conditions in the interstellar medium, protoplanetary disks, and comets. However, growing observational datasets and improved modelling have revealed discrepancies that question the reliability of spin temperatures. Nuclear spin conversion may occur in some environments, such as cometary comae or during ice processing in disks and the interstellar medium. The Team updates the spin temperature datasets, incorporate recent results including JWST observations, reassess laboratory and theoretical constraints, and clarify how spin ratios should be interpreted in the context of planet formation.

Team Leaders: Honghui Liu, University of Tübingen, Germany

Session: 20–24 April 2026

Abstract: Accreting black holes emit radiation across the electromagnetic spectrum, with X-rays arising from the innermost regions near the event horizon. X-ray spectroscopy and timing have greatly advanced our understanding of accretion processes, but model degeneracies and uncertain emission geometries limit our ability to answer key questions, such as the distribution of black hole spins. The launch of IXPE in 2021 reopened the X-ray polarimetry window, providing geometry-sensitive measurements that can break these degeneracies. While IXPE has already delivered important results for accreting black holes, a comprehensive framework integrating spectral, timing, and polarimetric data is still missing. This Team develops such a synergy framework and addresses new puzzles raised by IXPE, combining expertise in observations, theory, modelling, and simulations.

Team Leaders: Mihailo Martinovic, University of Arizona, USA, and Rodrigo Lopez, Research Center in the Intersection of Plasma Physics, Matter, and Complexity (P2mc), Chile

Session: 6–10 July 2026

Abstract: The solar wind is a natural laboratory for space plasma physics. In-situ measurements show that nonthermal features in particle velocity distribution functions, such as ion beams, are shaped by wave-particle interactions that drive the plasma toward quasi-steady non-equilibrium states. While linear, quasi-linear, and nonlinear theories describe many relevant processes, their relative importance in the evolving solar wind remains poorly constrained by observations. With high-resolution data from Parker Solar Probe and Solar Orbiter, including the former’s closest perihelion at 9.5 solar radii, we can now test these theories in the young solar wind. This project will unite experts in theory, simulations, and observations to determine how multiscale plasma models can explain solar wind evolution. The Team compares proton and alpha particle populations with linear and quasi-linear predictions, and use particles in cell and hybrid simulations to link small-scale kinetics with large-scale expansion effects, advancing multiscale models of the inner heliosphere.

Team Leaders: Christopher Piecuch, Woods Hole Oceanographic Institution, USA, and Julius Oelsmann, Tulane University, USA

Session: 19–23 January 2026

Abstract: Changes in the Atlantic meridional overturning circulation (AMOC) and sea level are major risks of global warming. A weakened AMOC could alter heat transport, storms, rainfall, and temperatures, while sea level rise threatens coasts. Because ocean circulation and sea level are closely linked, understanding their past relationship is essential for reliable future projections. Models suggest the AMOC may decline or even collapse this century, enhancing sea level rise along North Atlantic coasts. However, direct AMOC observations are short and sparse, leaving no robust benchmark to evaluate historical simulations and future projections. The Team combines observations, modelling, and theory to clarify the AMOC-sea level link and assess how satellite sea level data can improve ocean monitoring. This timely effort helps constrain past AMOC changes and refine projections of climate impacts.

Team Leaders: Marco Pinto, Laboratory fo Instrumentation and Experimental Particle Physics, Portugal, and Laura Rodríguez-García, European Space Agency, Spain

Session: 6–10 July 2026

Abstract: Solar energetic particles (SEPs) are intense bursts of protons, electrons, and ions accelerated in solar flares and coronal mass ejection shocks, reaching energies up to GeV. They pose serious risks to space exploration by damaging electronics, endangering astronauts, and disrupting planetary atmospheres. At Mars, SEPs can trigger global auroras and cause prolonged radio blackouts, threatening communication for future robotic and crewed missions. The mechanisms driving these disruptions, especially the role of different particle populations, remain unclear. The investigates how SEPs are accelerated and propagate from the Sun to Mars, and how they affect the Martian atmosphere and ionosphere. By combining expertise in particle physics, atmospheric science, instrumentation, and modelling, the Team aims to assess SEP impacts and improve space weather preparedness for Mars exploration.

Team Leaders: Francesco Pucci, CNR-ISTP, Italy, and Giulia Cozzani, LPC2E, CNRS, France

Session: 6–10 July 2026

Abstract: The heliosphere contains the turbulent solar wind, a plasma flow shaped by the Sun’s magnetic field. Turbulence plays a central role in energy dissipation, magnetic reconnection, particle acceleration, and shock dynamics. Yet, most global simulations of solar wind–planet interactions still treat the solar wind as laminar, despite clear observational evidence of its turbulent nature. A new 3D global kinetic code, Menura, now enables realistic simulations of the turbulent solar wind interacting with planetary magnetospheres. The Team combines such simulations with spacecraft observations to investigate how turbulence affects bow shocks, foreshock and magnetosheath regions, and overall magnetospheric dynamics in the Solar System and beyond. The project aims to constrain the role of turbulence in wind–planet interactions and advance both planetary and exoplanetary research.

Team Leaders: Nithin Sivadas, Catholic University of America, USA, and Maria-Theresia Walach, Lancaster University, UK

Session: 27 April–2 May 2026

Abstract: Geomagnetic indices, used to quantify solar-wind-driven geomagnetic activity, appear to saturate during extreme solar wind conditions. The cause of this nonlinear response is unclear and may reflect uncertainties in solar wind measurements rather than true physical saturation. If so, the geomagnetic impact of extreme space weather events could be underestimated. As solar maximum approaches and the likelihood of severe storms increases, the Team focuses on two key questions: what drives the observed nonlinear geomagnetic response, and how does geomagnetic activity respond to extreme solar wind parameters? By analysing a comprehensive database of solar wind data and geomagnetic indices, the researchers determine whether the apparent saturation is real or a statistical artifact. This work will improve understanding of extreme space weather and strengthen preparedness for future geomagnetic storms.

Team Leader: Alessio Spurio Mancini, Royal Holloway University of London, UK

Session: 19–22 January 2026

Abstract: Euclid is ESA’s flagship cosmology mission, launched in 2023 to map the distances, shapes, and positions of 1.5 billion galaxies over the past 10 billion years. A cornerstone of its science programme is the joint analysis of weak lensing and photometric galaxy clustering, known as the 3x2pt method, which enables precise tests of the standard cosmological model. To fully exploit Euclid Data Release 1, advanced modelling of systematics and improved inference methods are required. This project unites experts in data analysis, theory, statistics, and machine learning to develop optimised tools for the 3x2pt analysis. The initiative delivers high-impact publications, open software, and robust methodologies for future large scale surveys, maximising the scientific return of Euclid and strengthening the cosmology community.

Team Leader: Domenico Trotta, European Space Agency ESAC

Session: 13–17 July 2026

Abstract: Collisionless plasmas throughout the Universe contain suprathermal particle populations that extend beyond the thermal distribution. In the solar wind, electrons form four populations: a thermal core, an isotropic halo, a field aligned strahl up to about 2 keV, and a persistent higher-energy superhalo above about 2 keV whose origin remains unknown. Understanding the superhalo is key to explaining how electrons are injected into suprathermal energies and prepared for further acceleration. With new high-resolution measurements from Solar Orbiter, complemented by Parker Solar Probe and missions at 1 AU such as Wind and STEREO, we can now investigate this population in unprecedented detail. The Team combines observations and modelling to determine the origin of the electron superhalo and its evolution from the Sun to 1 AU.

Team Leaders: Sergey Tsygankov, University of Turku, Finland, and Roberto Taverna, University of Padova, Italy

Session: 9–13 February 2026

Abstract: Neutron stars are natural laboratories for extreme physics, where accretion, radiation, and strong magnetic fields interact. X-ray polarimetry was expected to clarify emission mechanisms and geometry, but recent observations from IXPE have revealed unexpected complexities that challenge current models. A major open issue is how to properly include quantum electrodynamics effects and radiation propagation in models of magnetar and X-ray pulsar atmospheres, where different approaches remain in disagreement. With next-generation X-ray polarimeters such as eXTP planned within the next five years, it is crucial to establish a robust theoretical and observational framework. This effort will help resolve current discrepancies and ensure accurate interpretation of future polarimetric data.

Team Leaders: Peter Wyper, Durham University, UK, and Joel Dahlin, University of Maryland, USA

Session: 11–15 May 2026

Abstract: Flare ribbons are chromospheric brightenings produced by energy deposition from particles accelerated during magnetic reconnection in solar flares. They display complex fine-scale structures that may provide key diagnostics of the reconnection process, yet their origin and interpretation remain unclear. This Team – combining observers and modellers – systematically characterises ribbon fine structure, assesses how well current models reproduce it, and determine what it reveals about coronal reconnection and energy release. The Team also defines new observational and modelling strategies to advance the field. This effort is timely given new high-resolution datasets from ground-based and space missions and increasingly realistic flare simulations that now reproduce ribbon fine structure.

Team Leaders: Mengyuan Xiao, University of Geneva, Switzerland, and Rohan Naidu, MIT, USA

Session: 2–6 February 2026

Abstract: The James Webb Space Telescope (JWST) has revealed a population of compact, red high-redshift sources known as Little Red Dots. These objects show broad Balmer lines, unusual V-shaped spectral energy distributions, and diverse properties that defy clear classification. They may represent the earliest growing black holes or extremely compact, massive galaxies, but no consensus has yet emerged. The Team combines multiwavelength observations, theoretical modelling, and JWST expertise to determine the nature of these sources. Using JWST archival data, dedicated programmes, and complementary observations from ALMA and Chandra, the researchers characterise their emission, environments, and possible active galactic nucleus signatures. Through focused meetings, the Team develops new analysis methods and refines models to clarify the role of Little Red Dots in early galaxy evolution and black hole growth.

Team Leaders: Andrzej Zdziarski, Nicolaus Copernicus Astronomical Center, Poland, and Alexandra Veledina, University of Turku, Finland

Session: 13–17 April 2026

Abstract: Black holes are defined by mass, charge, and spin, with spin ranging from zero to maximal rotation. Recent observations reveal a striking discrepancy: black holes in merging binaries detected by LIGO Virgo typically have low spins around 0.1, while those in accreting X-ray binaries often show high spins above 0.7, with many near maximal rotation. This tension challenges current models of black hole formation and evolution. The Team investigates three possible explanations: different formation channels for merging and accreting systems, systematic biases in X-ray spin measurements, and spin up through accretion during binary evolution. By bringing together experts in black hole formation, binary evolution, and accretion physics, the researchers analyse recent multi messenger data and refine theoretical models to establish reliable benchmarks for black hole spin estimates.