This session traditionally provides a forum for the discussion of all aspects of solar and heliospheric physics. Popular topics have included solar cycle dependencies of the Sun, solar wind and heliosphere, Coronal Mass Ejection research, studies of energetic particles throughout the heliosphere, and the outer boundaries of the heliosphere. We encourage contributions related to all ongoing and planned space missions, to ground-based experiments and to theoretical research. Papers presenting ideas for future space missions and experiments are very welcome in this session. The session will consist of both oral and poster presentations.

The Solar Orbiter mission, an international cooperation between ESA and NASA, is currently orbiting the Sun at heliocentric distances ranging from 0.95 to 0.29 au. Solar Orbiter now has an orbital inclination of 17 degrees and recently completed its first perihelion with this new perspective of the Sun’s poles in March 2025. As the mission continues towards an inclination of approximately 33 degrees, it is an exciting time to study dynamics within the inner heliosphere.

The overall goal of Solar Orbiter is to understand how the Sun creates and controls the heliosphere. The mission provides unprecedented imaging of the Sun’s photosphere, chromosphere, and corona, enabling studies of the origin and evolution of the Sun’s atmosphere, the solar wind, solar eruptions, and energetic particle events. The combination of high-resolution imaging and simultaneous in-situ measurements from Solar Orbiter’s inner-heliospheric vantage point offers a unique opportunity to link solar sources directly to their heliospheric impacts.

This session invites contributions that address the Solar Orbiter science objectives, exploit multi-mission data sets, and studies of the connections between the Sun and the heliosphere. We also welcome Solar Orbiter-related contributions in the fields of theory and numerical simulations that contribute to a better understanding of the solar origins of heliospheric variability and space weather.

The Sun’s atmosphere is the birthplace of multi-scale magnetic activity, e.g., flares, CMEs, jets, waves, and radio emissions, that drive a variety of solar physics phenomena such as the heating and acceleration of the coronal and solar wind plasma, particle energization and transport, and space weather throughout the whole heliosphere. For the first time in solar physics, the full extent of the solar corona can be systematically observed using a combination of space- and ground-based instruments from Parker Solar Probe, PROBA 3, SOHO, SDO, Solar Orbiter, PUNCH and Aditya-L1, complemented by ground-based observations, such as from DKIST and BBSO. By bringing together results from multiple instruments and approaches, the session aims to provide a comprehensive overview of how today’s coronal observations are advancing our understanding of coronal structure, dynamics, and magnetic fields, and can also serve as a forum to discuss future synergies and observational strategies. We welcome contributions to all aspects of research addressed to exploring the inner heliosphere and solar corona, with a particular focus on the new observations, such as from PSP’s closest approaches and Proba 3.

Coronal mass ejections (CMEs) can be listed amongst the most extreme manifestations of the Sun’s dynamic activity and are prominent drivers of space weather disturbances at Earth as well as other solar system bodies. Over the past few decades, remarkable advances through remote-sensing and in-situ measurements combined with analytical and MHD modeling have been made, but many fundamental questions remain regarding CME formation and eruption mechanisms, early coronal evolution, 3D interplanetary configuration, and interactions with the structured solar wind and other transients. As we pass the maximum of Solar Cycle 25, it is important to reassess our current knowledge and identify promising avenues to advance CME observation, analysis, modeling, and forecasting capabilities.

This session encourages contributions that advance CME science across a wide range of approaches, taking advantage of the wealth of currently available observational data and models. We welcome presentations employing remote-sensing and/or in-situ observations, multi-spacecraft studies, modeling efforts focusing on CME eruption and/or propagation, and mission concepts that can significantly advance fundamental research while addressing remaining observational and knowledge gaps. Particular emphasis will be given to contributions employing novel theories, measurements, and techniques.

Collisionless shocks are ubiquitous in the universe, occurring in diverse astrophysical environments, from planets to galaxy clusters. Significant efforts have been made to understand their rich dynamics and their effects on the surrounding environment, including particle thermalization and acceleration, turbulence generation, and the evolution of various transient phenomena.

Heliospheric shocks offer the unique advantage of being directly accessible by in situ measurements. Missions, such as Solar Orbiter, STEREO, and Parker Solar Probe, have deepened our knowledge of interplanetary shocks and the associated regions, while MMS, Cluster, THEMIS, Cassini, Maven, and others have similarly enhanced our knowledge of planetary bow shocks.

High-performance computing has also played a critical role in filling key knowledge gaps, enabling global and local simulations to provide insights into the nature of collisionless shocks.

Despite these efforts, many questions remain open. In particular, we still do not fully understand the mechanisms associated with certain aspects of particle heating and acceleration, wave generation, wave-particle interaction, and energy redistribution at shocks. The interplay of collisionless shocks and pre-existing plasma turbulence also remains poorly understood. Additionally, details about the formation and impact of transient structures, such as hot flow anomalies, foreshock bubbles, cavitons, spontaneous hot flow anomalies, magnetosheath jets, etc., are still unknown.

We thus welcome observational, numerical, and theoretical works that explore plasma processes at collisionless shocks and surrounding regions.

The heliosphere is permeated by several species of suprathermal and energetic particles (protons, electrons, heavy ions), exhibiting a diverse range of energy spectra and originating at different heliospheric and interstellar locations. Such energetic particles are of paramount importance to address many unconstrained aspects of energy conversion in astrophysical systems, as well as being impactful to society as they can pose a hazard to both human activities and technological systems in space. Suprathermal particles, in particular, are a key population that bridges the low-energy (1 keV in the heliosphere) plasma and high-energy (> 1 MeV) population, often treated independently.

The dynamics of suprathermal and energetic particles in the heliosphere encompass various processes, from the acceleration of solar wind electrons/ions to solar energetic particle events related to solar eruptive phenomena. Despite decades of research, several aspects of suprathermal and energetic particle production remain unknown, with the main candidate production mechanisms being magnetic reconnection, collisionless shocks and several categories of wave-particle interactions. How suprathermal and energetic particles are transported through the heliosphere is also object of active debate, and largely unconstrained. Recent missions, such as Solar Orbiter and Parker Solar Probe, have delivered excellent observations from the inner heliosphere, both remotely and in situ. When combined with data from missions like ACE, SOHO, Wind, and STEREO at 1 AU, these observations across varying radial distances offer an unprecedented opportunity to characterize the sources and transport mechanisms of suprathermal and energetic particles in the heliosphere.

This session invites contributions that explore space-borne and ground-based observations, as well as theoretical and modelling approaches, to deepen our understanding of the acceleration and transport of suprathermal and energetic particles in the heliosphere. We encourage submissions that provide new insights, propose innovative methodologies, or synthesize data across multiple missions to address these critical scientific challenges.

The heliosphere is a unique astrophysical system and example astrosphere that can be explored directly with spacecraft, providing a natural laboratory for studying the fundamental processes that shape the observable Universe. Key challenges include understanding how variability in the solar wind drives heliospheric dynamics, how particles are accelerated across different heliocentric distances, and how the heliosphere couples to the local interstellar medium.
NASA’s Interstellar Mapping and Acceleration Probe (IMAP), scheduled for launch in September 2025 to a deep-space orbit around the Earth–Sun L1 point, will open a new observational window on particle acceleration throughout the heliosphere and on the connections between the Sun, the heliosphere, and the local interstellar environment. IMAP will also complement the existing fleet of near-Earth spacecraft, enabling coordinated multi-mission investigations with unprecedented detail.
For this session, we invite contributions from across the heliophysics and astrophysics communities, including theoretical studies, modelling efforts, and data analyses from both current and past missions. We particularly encourage work addressing particle acceleration from 1 au to the heliopause, sampling of interstellar material, and the dynamics of the heliospheric boundary regions. New results on Sun–heliosphere–interstellar coupling, multi-mission studies in near-Earth space, and early IMAP science findings are especially welcome.

The session solicits contributions that report on nonthermal solar and planetary radio emissions. Coordinated multi-point observations from ground radio telescopes (e.g., LOFAR, LOIS, LWA1, URAN-2, UTR-2) and spacecraft plasma/wave experiments (e.g., BepiColombo, Solar Orbiter, Parker Solar Probe, UVSQ-Sat, Inspire-Sat 7, Cassini, Cluster, Demeter, Galileo, Juno, Stereo, Ulysses and Wind) are especially encouraged. Presentations should focus on radiophysics techniques used and developed to investigate the remote magnetic field and the electron density in solar system regions, like the solar corona, the interplanetary medium and the magnetized auroral regions. Interest also extends to laboratory and experimental studies devoted to the comprehension of the generation mechanisms (e.g., cyclotron maser instability) and the acceleration processes (e.g., Alfven waves). Further preparations, evaluations, investigations, analyses of forthcoming space missions or nanosatellites (like Juice, SunRISE, UVSQ-Sat NG…) are also welcome.

This session focuses on the non-linear processes taking place in space, laboratory, and astrophysical plasma. In many cases, these processes are not separated but appear interlinked. For instance, magnetic reconnection is an established ingredient of the turbulence cascade, and it is also responsible for the production of turbulence in reconnection outflows; shocks can be accountable for turbulence formation, for example, in the turbulent magnetosheath, or can be efficient particle accelerators through their interaction with the ambient turbulence.

The study of these processes has seen significant progress in recent years thanks to a synergistic approach based on simulations and observations. On the one hand, simulations can deliver output in a temporal and spatial range of scales, going from fluid to electron kinetic. That is partially also due to the advent of GPU facilities that contribute to increasing computational algorithms' power in plasma physics. On the observational side, high cadence measurements of particles and fields and high-resolution 3D measurements of particle distribution functions are currently provided by the missions MMS, Parker Solar Probe, and Solar Orbiter, opening new research scenarios in heliophysics and providing a consistent amount of new data to be analysed. Furthermore, other present and future missions that will give unique plasma measurements around solar system compact objects, such as Bepi Colombo, Juice, Comet Interceptor, and HelioSwarm are demanding the development of new numerical tools for a successful interpretation of the observations.

This session welcomes simulation, observational, and theoretical works relevant to studying the abovementioned processes. We also encourage papers proposing new methods in simulation techniques and data analysis, for example, those rooted in Artificial Intelligence or those based on multi-point satellite observations.

Space and astrophysical plasmas are typically in a turbulent state, exhibiting strong fluctuations of various quantities over a broad range of scales. These fluctuations are non-linearly coupled, and this coupling leads to the transfer of energy (and other quantities, such as cross helicity and magnetic helicity) from large to small scales and to dissipation. Turbulent processes are relevant for the heating of the solar wind and the corona, and the acceleration of energetic particles. In these environments, many aspects of turbulence are not well understood, in particular, the injection and onset of the cascade, the cascade itself, the dissipation mechanisms, as well as the role of coherent structures and waves. Specific phenomena such as magnetic reconnection, shock waves, solar wind expansion, plasma instabilities, wave activity and their relationship with the turbulent cascade and dissipation are under debate. The session will explore these open questions through observational, theoretical, numerical, and laboratory studies, aiming to advance our understanding of these processes. For observational studies, we welcome contributions utilizing data from a wide range of relevant spacecraft missions, including WIND, CLUSTER, MMS, STEREO, THEMIS, Van Allen Probes, and DSCOVR, with particular emphasis on recent findings from Solar Orbiter and Parker Solar Probe.

Are you unsure about how to bring order in the extensive program of the General Assembly? Are you wondering how to tackle this week of science? Are you curious about what EGU and the General Assembly have to offer? Then this is the short course for you!

During this course, we will provide you with tips and tricks on how to handle this large conference and how to make the most out of your week at this year's General Assembly. We'll explain the EGU structure, the difference between EGU and the General Assembly, we will dive into the program groups and we will introduce some key persons that help the Union function.

This is a useful short course for first-time attendees, those who have previously only joined us online, and those who haven’t been to Vienna for a while!

This open session traditionally invites presentations on all aspects of the Earth’s magnetospheric physics, including the magnetosphere and its boundary layers, magnetosheath, bow shock and foreshock as well as solar wind-magnetosphere-ionosphere coupling. We welcome contributions on various aspects of magnetospheric observations, remote sensing of the magnetosphere’s processes, modelling and theoretical research. The presentations related to the current and planned space missions and to the value-added data services are also encouraged. The comparative studies of the processes in the Earth’s and other planets’ magnetospheres are welcomed. This session is particularly suitable for any contribution which does not fit more naturally into one of the specialised sessions and for contributions of wide scientific interest.

Understanding plasma energisation and energy transport is one of the major challenges in the field of space plasma physics. Key regions where fundamental processes such as plasma heating, shock formation and re-formation, magnetic reconnection, turbulence, wave-particle interactions, plasma jets braking, and combinations of these initiate and govern particle energisation and energy transport include the solar atmosphere, the solar wind and the Earth's foreshock, bow shock, magnetosheath, magnetopause, magnetotail current sheet, and transition region.

Due to their proximity, these regions provide excellent laboratories in which to study such processes. Near Earth, the ESA/Cluster and NASA/MMS four-point constellations, as well as the large-scale multipoint NASA/THEMIS mission, have greatly improved our understanding of these plasma processes compared to earlier single-point measurements. However, these missions have also revealed that these processes operate across multiple scales, ranging from large fluid scales to smaller kinetic scales. This implies that multi-scale in situ observations are critical. To resolve scale coupling and ultimately fully understand plasma energisation and energy transport processes, simultaneous measurements at both fluid and kinetic scales are required. Building on previous single-scale missions, the Plasma Observatory (PO) mission represents the next generation of space plasma physics investigations. PO is a seven-spacecraft, multi-scale mission concept designed to study plasma energisation and energy transport in the Earth's magnetosphere simultaneously at fluid and ion scales. These are the scales at which the largest amount of electromagnetic energy is converted into energised particles and energy is transported. Any modelling approach, from global to kinetic, can be applied here.

We particularly welcome studies integrating numerical modeling, theoretical investigations and in-situ measurements/remote observations from past, current and future space missions such as Cluster, MMS, PO, Parker Solar Probe, Solar Orbiter, Bepi Colombo, SMILE, HelioSwarm, SPO...

Magnetic reconnection and the Kelvin–Helmholtz instability (KHI) are two fundamental plasma processes that govern magnetic topology changes and plasma transport in a wide range of space and astrophysical environments. Magnetic reconnection is responsible for many explosive phenomena in space, while KHI occurs from the MHD scale to the electron kinetic scale. Magnetic reconnection can trigger the KHI and can be triggered in the process of KHI. Both of them play a dominant role at the boundaries between the solar wind and planetary magnetospheres, such as those of Earth, Mercury, Jupiter, and Saturn. Recent advances driven by high-resolution in situ measurements from spacecraft missions (e.g., MMS, Cluster, THEMIS, JUNO, MAVEN, Parker Solar Probe) and by state-of-the-art numerical simulations have led to significant progress in understanding these processes over the past several years.

Despite the advances, many key issues remain unresolved. In reconnection, the triggering mechanisms, quantitative aspects of the energy conversions, identification of the electron diffusion/dissipation region, and coupling across multiple scales remain unsolved. In KHI, plasma mixing across the boundary, an energy cascade from the large-scale vortices to kinetic scales, and the nonlinear evolution of the secondary modes are central issues. Furthermore, the interplay between reconnection and KHI introduces many new challenges. This joint session invites presentations on all of the aspects associated with magnetic reconnection and KHI from the spacecraft measurements, theoretical analysis, numerical simulations, and laboratory experiments.

In the collisionless space plasmas of magnetospheres and the solar wind, energy and momentum transfer between charged particles is mediated by waves. Wave-particle interactions govern the generation of waves through linear and nonlinear resonance and their damping or amplification along propagation paths, as well as the formation of high-energy tails in particle distributions and the heating of cold particle populations. Progress in understanding these processes and their impact on both microscopic and macroscopic plasma kinetics is driven by a combination of simulation studies and in-situ measurements from past missions (Van Allen Probes, Cluster, Cassini) and ongoing missions (Arase, MMS, THEMIS, MAVEN, Juno, Parker Solar Probe, Solar Orbiter), as well as multiple CubeSat missions (ELFIN, FY, CIRBE) that provide high-resolution observations of particle precipitation. These observations reveal both similarities and differences in wave-particle interactions across the solar wind, Earth’s radiation belts, and planetary magnetospheres, motivating rapid development of new theoretical frameworks, including effects of nonlinear and non-resonant interactions and their incorporation into traditional quasilinear diffusion models. The aim of this session is to bring together experts in wave-particle interaction theory, specialists on spacecraft observations of plasma waves and particles, and developers of next-generation computational models.

This session is formed by merging ST2.6 and ST2.7, bringing together perspectives on multiscale and global coupling in the solar wind–magnetosphere–ionosphere system. The solar wind supplies energy, momentum, and mass to geospacer, driving interconnected processes that link the bow shock, magnetosheath, magnetopause, magnetotail, inner magnetosphere, ionosphere. At the global scale, we aim to explore how solar wind energy input and reconnection-driven convection control the development geomagnetic storms and substorms.At regional and mesoscale levels, we welcome studies on plasma flows, magnetosphere–ionosphere current systems, magnetic reconnection, boundary layer instabilities (e.g., Kelvin–Helmholtz), flux transfer events, ULF waves, ionospheric convection, auroral arcs, and related phenomena. Emphasis is placed on linking these processes to specific solar wind conditions and elucidating their roles in system-level responses. We invite contributions that integrate data from space missions (e.g., THEMIS, Cluster, MMS, RBSP), ground-based observatories (e.g., SuperDARN, magnetometers, optical networks), and numerical or machine learning models. This session supports the upcoming SMILE mission by promoting studies aligned with its science goals on solar wind–magnetosphere–ionosphere coupling.

The Earth’s inner magnetosphere hosts diverse charged particle populations, including the Van Allen belts, ring current, and plasmaspheric particles, with energies from eV to MeV. Interactions among these populations provide feedback mechanisms that shape magnetospheric dynamics. For example, ring current particles generate EMIC and chorus waves, which regulate radiation belt evolution through wave–particle interactions. Ring current electrons may be accelerated to relativistic energies, while the plasmasphere modulates these processes. Coupling extends beyond the magnetosphere: precipitation affects the ionosphere, while ionospheric upflows supply plasma back into the magnetosphere. Understanding these processes is vital for fundamental science and for improving space weather forecasting.

Particle precipitation into planetary atmospheres is a key heliophysical process, controlled by solar wind, magnetospheric, and ionospheric interactions. At Earth, precipitation channels energy into the upper atmosphere, producing aurora, ionospheric currents, and enhanced satellite drag. These processes demonstrate the coupling of plasma regimes and their consequences for both natural variability and technological systems. This session emphasizes a system-science perspective on precipitation across a wide range of energies and impacts. We invite studies on the roles of different drivers, the spatiotemporal dynamics of solar wind structures and geomagnetic storms, and the effects on ionospheric conductivity, atmospheric chemistry, and dynamics.

Comparative studies of outer planet magnetospheres, shaped by unique but related drivers, further highlight universal coupling processes. We welcome theoretical, modeling, and observational contributions on the dynamics of inner magnetospheres at Earth and other planets, including magnetosphere–ionosphere coupling and responses to solar wind disturbances. Relevant datasets include MMS, THEMIS, Van Allen Probes, Arase, Cluster, LEO satellites, CubeSats, Juno, SuperDARN, magnetometers, optical imagers, incoherent scatter radars, and ground-based VLF measurements.

Cosmic rays carry information about space and solar activity, and, once near the Earth, they produce isotopes, influence genetic information, and are extraordinarily sensitive to water. Given the vast spectrum of interactions of cosmic rays with matter in different parts of the Earth and other planets, cosmic-ray research ranges from studies of the solar system to the history of the Earth, and from health and security issues to hydrology, agriculture, and climate change.
Although research on cosmic-ray particles is connected to a variety of disciplines and applications, they all share similar questions and challenges regarding the physics of detection, modeling, and the influence of environmental factors.

The session brings together scientists from all fields of research that are related to monitoring and modeling of cosmogenic radiation. It will allow the sharing of expertise amongst international researchers as well as showcase recent advancements in their field. The session aims to stimulate discussions about how individual disciplines can share their knowledge and benefit from each other.

We solicit contributions related but not limited to:
- Health, security, and radiation protection: cosmic-ray dosimetry on Earth and its dependence on environmental and atmospheric factors
- Planetary space science: satellite and ground-based neutron and gamma-ray sensors to detect water and soil constituents
- Neutron and Muon monitors: detection of high-energy cosmic-ray variations and its dependence on local, atmospheric, and magnetospheric factors
- Hydrology and climate change: low-energy neutron sensing to measure water in reservoirs at and near the land surface, such as soil, snowpack, and vegetation
- Cosmogenic nuclides: as tracers of atmospheric circulation and mixing; as a tool in archaeology or glaciology for dating of ice and measuring ablation rates; and as a tool for surface exposure dating and measuring rates of surficial geological processes
- Detector design: technological advancements in the detection of cosmic rays and cosmogenic particles
- Cosmic-ray modeling: advances in modeling of the cosmic-ray propagation through the magnetosphere and atmosphere, and their response to the Earth's surface
- Impact modeling: How can cosmic-ray monitoring support environmental models, weather and climate forecasting, agricultural and irrigation management, and the assessment of natural hazards

The importance of ionospheric research is on the rise with the development of modern terrestrial and space-based technologies, as the ionosphere reflects and modifies the radio waves used for communication and navigation. Coupling processes are crucial to our understanding of ionospheric dynamics and variability. The ionosphere is influenced from above by various solar and magnetospheric processes. The strongest of these are well-developed magnetic storms, but many others remain insufficiently explored. Conversely, the ionosphere is primarily (though not exclusively) forced from below by atmospheric waves such as planetary, tidal and acoustic-gravity waves. This symposium invites observational, simulation and modelling studies that address ionospheric dynamics with an emphasis on magnetospheric and lower atmospheric forcing, as well as the associated feedback on ionospheric behaviour.
New results focusing on the comparison of the latitudinal, seasonal and hemispherical effects of magnetic storms and substorms on the ionosphere are particularly welcome. Regarding atmospheric forcing, contributions focusing on atmospheric waves, wave-wave interactions, wave-mean flow interactions, atmospheric electricity, and electrodynamic coupling processes are sought. Contributions focusing on ionospheric effects from other sources, such as the solar terminator, solar eclipses, seismic activity or human-made explosions, are also welcome.

Machine learning approaches have shown remarkable results for the thermosphere, ionosphere, plasmasphere, and magnetosphere. This session also welcomes innovative approaches that include data assimilation, machine learning, empirical or numerical modeling to disclose interconnections and feedback within these complex systems.

The Earth's middle atmosphere, mesosphere, and lower thermosphere (MLT) region provide a great platform for studying ionospheric dynamics, disturbances, eddy mixing, atmospheric drag effects, and space debris tracking. The thermal structure of these regions is influenced by numerous energy sources such as solar radiation, chemical, and dynamical processes, as well as forces from both above (e.g., solar and magnetospheric inputs) and below (e.g., gravity waves and atmospheric tides). Solar atmospheric tides, related to global-scale variations of temperature, density, pressure, and wind waves, are responsible for coupling the lower and upper layers of the atmosphere and significantly impact their vertical profiles in the upper atmosphere. With evidence of climate change impacts on the middle and upper atmosphere, monitoring and understanding trends through observational data is critical. There has been a contraction of the stratosphere and a decrease in the density of the upper atmosphere, which could impact the accumulation of space debris. This session invites presentations on scientific work related to various experimental/observational techniques, numerical and empirical modeling, and theoretical analyses on the dynamics, chemistry, and coupling processes in the altitude range of ~ 20 km to 180 km of the middle atmosphere and MLT regions, including long-term climatic changes.

Low-Earth-orbit (LEO) satellites provide unique opportunities to characterize the Earth's magnetic field, ionospheric currents and plasma parameters, and thermosphere density and winds across a wide spectrum of time and spatial scales, and for a large range of solar and geomagnetic activities. At the forefront of this advance are the three ESA Earth Explorer Swarm satellites, which have been providing high-accuracy measurements of the Earth's magnetic field, electric field, plasma parameters, precise-orbit determination, and accelerometer observations since their launch in November 2013. They have proven very valuable for studying the near-Earth magnetic field and the coupled ionospheric-thermospheric environment, and enabled the development and implementation of advanced models and operational space weather services. The scientific potential of the polar-orbiting Swarm satellites is today augmented by newly available data, especially those collected by the low-inclination Macau Science Satellite 1 and CSES satellites.
In addition, the ESA Scout NanoMagSat constellation, consisting of one near-polar and two 60° inclination satellites, is scheduled to launch near the end of 2027, with full operation planned for 2028. It will acquire high-accuracy magnetic vector and scalar data, electron density, and electron temperature
data, navigation data, and collect ionospheric radio-occultation profiles. All these data are also complemented by increasingly available platform-magnetometer data, such as from the CryoSat-2, GRACE, GRACE-FO, GOCE, and E-POP satellites. The new abundance of satellite data provides unprecedented space-time data coverage at LEO satellite altitudes, opening the way for new scientific opportunities.

The Earth’s atmosphere and ionosphere are subject to significant variability associated with solar and space forcing. While this is predominantly relevant at high latitudes, midlatitudes can also be affected as observed during severe geomagnetic storms that occurred e.g. in 2024–2025. While in situ observations of the ionosphere and mesosphere–lower-thermosphere are only possible with spacecraft and sounding rockets, a wealth of information is obtained thanks to remote sensing techniques using ground-based instruments.
For instance, ground-based magnetometers, used in dense networks, routinely enable the derivation of ionospheric currents and geomagnetic indices. Optical instruments not only encompass imagers observing auroral and airglow emissions, but also consist of scanning Doppler imagers, Fabry-Perot interferometers, and lidars which measure upper atmospheric winds and temperatures, in particular in the thermosphere and mesosphere. Besides, visible spectrometers disentangle the spectral signatures of different auroral processes, enabling discrimination between precipitation-driven emissions and signatures of thermospheric heating. Ionospheric parameters can also be measured with radars, spanning a wide range of active (ionosondes, meteor radars, coherent and incoherent scatter radars, VLF transmitters) and passive (riometers, VLF receivers, GNSS receivers) systems. With increased interest in understanding space weather and atmosphere coupling as a system, polar atmospheric composition measurements of the middle atmosphere are also valuable. Finally, citizen science data such as images taken by aurora chasers are increasingly used to complement observations from instruments.
Combining ground-based observations from various instruments enables the development of novel data analysis methodologies that can provide access to physical quantities previously difficult to quantify, such as Joule heating. Ground-based measurements are also increasingly valuable for data assimilation into numerical models, thanks to which we can both enhance our understanding of the underlying physics of ionosphere–atmosphere processes and improve our space weather forecasting capability.
In this session, we invite contributions featuring the use of ground-based instruments in studies of the ionosphere–atmosphere system at polar and mid-latitudes. We welcome contributions of space weather and ionospheric–atmospheric physics processes of various time and spatial scales.

This session invites contributions on the latest developments and results in lidar remote sensing of the atmosphere, covering • new lidar techniques as well as applications of lidar data for model verification and assimilation, • ground-based, airborne, and space-borne lidar systems, • unique research systems as well as networks of instruments, • lidar observations of aerosols and clouds, thermodynamic parameters and wind, and trace-gases. Atmospheric lidar technologies have shown significant progress in recent years. While, some years ago, there were only a few research systems, mostly quite complex and difficult to operate on a longer-term basis because a team of experts was continuously required for their operation, advancements in laser transmitter and receiver technologies have resulted in much more rugged systems nowadays, many of which are already operated routinely in networks and several even being fully automated and commercially available. Consequently, also more and more data sets with very high resolution in range and time are becoming available for atmospheric science, which makes it attractive to consider lidar data not only for case studies but also for extended model comparison statistics and data assimilation. Here, ceilometers provide not only information on the cloud bottom height but also profiles of aerosol and cloud backscatter signals. Scanning Doppler lidars extend the data to horizontal and vertical wind profiles. Raman lidars and high-spectral resolution lidars provide more details than ceilometers and measure particle extinction and backscatter coefficients at multiple wavelengths. Other Raman lidars measure water vapor mixing ratio and temperature profiles. Differential absorption lidars give profiles of absolute humidity or other trace gases (like ozone, NOx, SO2, CO2, methane etc.). Depolarization lidars provide information on the shapes of aerosol and cloud particles. In addition to instruments on the ground, lidars are operated from airborne platforms in different altitudes. Even the first space-borne missions are now in orbit while more are currently in preparation. All these aspects of lidar remote sensing in the atmosphere will be part of this session.

This open session provided an in-depth exploration of Space Weather and Space Climate phenomena, focusing on the dynamic processes occurring from the Sun to Earth. Key topics included solar activity, such as solar flares and coronal mass ejections, and their interactions with Earth's magnetosphere, ionosphere, and thermosphere. Discussions also highlighted the impacts of these processes on satellite operations, communication systems, power grids, and Earth's climate, emphasising both immediate space weather effects and longer-term space climate influences on technological and natural systems.

Space weather and space climate encompass the dynamic interactions between the Sun and Earth, occurring across timescales from minutes to decades. These interactions involve processes occurring at the Sun, in the heliosphere, magnetosphere, ionosphere, thermosphere, and lower atmosphere. Key drivers include coronal mass ejections (CMEs), interplanetary shocks, and solar energetic particle (SEP) events. Predicting extreme space weather events and developing mitigation strategies is essential because space assets and critical infrastructures, such as satellite systems, communication and navigation networks, power grids, and aviation operations, are highly sensitive to the space environment. Conducting post-event analyses is crucial for improving and maintaining numerical models that can predict extreme space weather events and prevent the failure of critical infrastructures.

This session focuses on the current state of space weather products and explores new ideas and developments that can improve our understanding of space weather and space climate and their impact on critical infrastructure. We invite contributions on topics including, but not limited to: forecasting and nowcasting tools and services; satellite observations and data assimilation techniques; numerical model development, validation, and verification; machine learning applications in space weather prediction; generation and refinement of solar, geomagnetic, and ionospheric indices. We particularly welcome interdisciplinary and collaborative approaches that bridge research and operational communities. Contributions that address the drivers and the real-world impacts of space weather on systems such as aviation, pipelines, power distribution, human spaceflight, and auroral tourism are strongly encouraged.

Extreme space weather events, including major solar flares, solar energetic particle events, and severe geomagnetic storms, pose significant risks to space‑ and ground‑based infrastructure. Their rarity but potentially high impact highlights the limitations of current monitoring, modelling, and forecasting capabilities, especially for extreme or poorly observed scenarios. Strengthening resilience requires advanced modelling approaches supported by sustained, near‑real‑time observations across the near‑Earth environment.

This session focuses on the combined use of space weather missions, instrumentation, and models to observe, understand, and predict extreme events and their effects on the heliosphere, magnetosphere, ionosphere, thermosphere, auroral regions, and radiation belts. Continuous and timely measurements are essential to capture event initiation and evolution, quantify environmental impacts, and provide robust boundary conditions and validation data for physics‑based and data‑driven models.

We have welcomed contributions showcasing the capabilities of current and upcoming missions and instruments measuring plasma properties, electromagnetic fields, radiation, and atmospheric response. Particular emphasis is placed on how these observations enable near‑real‑time situational awareness, support data assimilation, and help close critical observational gaps during severe events through coordinated multi‑mission strategies and hosted payloads.

The session also addresses advances in space weather modelling and forecasting, including physics‑based modelling, machine‑learning approaches, and hybrid techniques. We promote contributions evaluating model performance during extreme events, identifying key physical and observational limitations, and proposing paths to improved predictive skill. Topics include uncertainty quantification, extreme‑event benchmarks, and translating model outputs into actionable information for operational and pre‑operational services.

By bringing together instrument developers, mission teams, modellers, and forecasters, this session aims to strengthen the connection between observations and models and to advance end‑to‑end capabilities for monitoring and forecasting extreme space weather.

The ionospheres and (induced) magnetospheres of unmagnetized and weakly magnetized bodies with (substantial) atmospheres (e.g. Mars, Venus, Titan, Pluto and comets) are subject to disturbances due to solar activity, interplanetary conditions (e.g. solar flares, coronal mass ejections and solar energetic particles), or for moons, parent magnetospheric activity. These objects interact similarly as their magnetized counterparts but with scientifically important differences.
As an integral part of planetary atmospheres, ionospheres are tightly coupled with the neutral atmosphere, exosphere and surrounding plasma environment, possessing rich compositional, density, and temperature structures. The interaction among neutral and charged components affects atmospheric loss, neutral winds, photochemistry, and energy balance within ionospheres.
This session invites abstracts concerning remote and in-situ data analysis, modelling studies, comparative studies, instrumentation and mission concepts for unmagnetized and weakly magnetized solar system bodies.

Rocket launches and re-entries of reusable and discarded objects adds familiar and exotic anthropogenic trace gases and aerosols to all layers of the atmosphere. The space sector is the only anthropogenic source released directly to the middle and upper layers of the atmosphere. Once emitted to these layers, pollutants persist for years, leaving a long legacy of atmospheric pollution. These pollutants are increasingly ubiquitous due to recent exponential space sector growth, yet there are no regulatory controls targeting these emissions. Quantification of the complex and unique effects on the atmosphere is hindered by many uncertainties and data gaps, such as the chemical composition of exhaust from novel propellants, the resultant evolution during plume afterburning, the locations and trajectories of ablative re-entry, the radiative and chemical kinetic properties of the pollutants, and the physical and chemical evolution of controlled and uncontrolled re-entry. Lack of openly-available modelling tools is compounded by a scarcity of real-world experiments and observations, and future scenarios are hindered by a lack of commercial space activity data or well-supported growth projections. This session invites submissions across all geophysical and related disciplines in and beyond academia to share planned, current, or ongoing research that provides new knowledge in this area, explores and devises new open-source modelling techniques, or exposes methodological gaps that need to be resolved to inform sustainability initiatives and global regulation. We are also interested in innovative methods adopted by researchers in other domains that could be applied to advance understanding of environmental harm from the space sector. These include related topics such as geoengineering, space weather, space engineering, upper atmosphere circulation and chemistry, and meteors.

The rapid growth of missions, observatories, and monitoring systems in the heliosphere, across the Solar System and from terrestrial or airborne facilities has created an unprecedented volume and diversity of data. Making sense of these observations requires methods that can both process large datasets efficiently and extract meaningful physical insight. Machine learning has become an important tool in this effort, complementing established physics-based approaches by enabling new ways of discovering patterns, building predictive models, and working with complex or incomplete measurements.

In recent years, increasing attention has been given to hybrid methods that combine machine learning with physical models. These approaches are now being applied across planetary and heliophysical domains, from forecasting solar eruptions and solar wind conditions, to automating the analysis of planetary surfaces or improving on-board data handling. They demonstrate how data-driven methods can benefit from physical knowledge, while physics-based models can be improved through modern data analysis techniques.

This session aims to provide an inclusive and interdisciplinary forum for researchers applying machine learning in planetary sciences and heliophysics, as well as those developing methods at the intersection between data-driven and physics-based approaches. We particularly encourage contributions that illustrate the wide range of applications, encourage exchange between disciplines and showcase the transition from research to operations.