During geomagnetic storms, Joule heating is a major heating source of the upper atmosphere that is not well estimated, due to a lack of measurements. This leads to uncertainties in orbital calculations. We present simulations with commonly used physics-based models and empirical models that provide measurements of Joule heating. The results show great discrepancies, pointing to the need for measurements in the Earth's Lower Thermosphere-Ionosphere at altitudes where Joule heating maximizes.

Heliophysics spans a wide range of disciplines covering the study of the Sun and the different Solar System bodies, such as Earth and other planets, moons, comets, and asteroids, and their interactions with the Sun, focusing on plasma and atmospheric processes. A grass-roots effort has been recently started toward establishing a European Heliophysics Community (https://www.heliophysics.eu/). This white paper outlines the motivation, priorities, and a future vision of Heliophysics in Europe.

We applied machine learning to investigate how the solar wind and Earth's geomagnetic activity control the position of the magnetopause, the boundary layer of Earth's magnetic field. Our results demonstrate that geomagnetic activity strongly influences this boundary and should be incorporated in predictive models. Using data from multiple spacecraft, we developed a simple mathematical description of the magnetopause distance that improves understanding of solar wind–magnetosphere interactions.

The ionosphere is where Earth’s atmosphere overlaps with a gas of charged particles in space. There, collisions with neutral air and electromagnetic forces driven by the solar wind control plasma motion. We created a global model that includes magnetic induction, explaining how electric currents and fields change, offering a more accurate view of atmosphere–space coupling than conventional models based on electric circuits.

Space plasmas often deviate from the usual thermal pattern assumed in standard models. Using the modified Kappa distribution, we derived how this non-standard energy spread alters electrical flow, heat transfer, and particle motion. We found that stronger deviations increase collision rates and weaken transport coefficients, while normal behaviour returns in the thermal limit, improving our insight into space environments.

Key properties of the ionospheric electrodynamics are electric fields, currents, and conductances. They provide a window to the vast and distant near-Earth space, cause Joule heating that affect satellite orbits, and drive geomagnetically induced currents (GICs) in technological conductor networks. We have developed a new method for solving the key properties of ionospheric electrodynamics from ground-based magnetic field observations.

We studied how solar eclipses affect the electric field in the atmosphere and the movement of charged particles above Earth near the magnetic equator. Using ground-based instruments in Peru, we found that eclipses can lead to significant changes, depending on weather conditions. These results help us better understand how solar events influence the near-Earth environment and its connection to the upper atmosphere.

This study investigates the ionospheric signatures of a Bursty Bulk Flow in Earth’s magnetotail using a global 6D hybrid-Vlasov simulation coupled with an ionospheric model. The results show that a reconnection-driven Bursty Bulk Flow generates vortices that produce field-aligned currents, which map to the ionosphere with a distinct east–west orientation and exhibit a characteristic westward drift. Variations in ionospheric observables are identified as clear signatures of this flow.

Plasma convection is the movement of plasma that drags the magnetic field lines with it. Magnetic field in the solar wind interacts with the Earth's magnetic field and drags the dayside field lines of the Earth's magnetosphere toward nightside, causing the plasma inside the magnetosphere to circulate around the Earth in a process called the Dungey Cycle. Our simulation and methodology desribe this cycle in detail and find features in the convection that are not explained by fluid models.

This study uses images taken by the Swedish satellite MATS (Mesospheric Airglow Tomography and Spectroscopy) to conduct a statistical analysis of the molecular oxygen atmospheric band emissions in the aurora. This auroral emission can not be observed from the ground, making it one of the least understood auroral emissions. Our results provide a new dataset with information on the peak altitude, geomagnetic location, and auroral intensity of 378 events detected between February and April 2023.

Space weather can cause electric currents to flow through the ground at the Earth’s surface. These currents correspond closely to the rate of change of the magnetic field, following Faraday’s law of induction. The scientific community regularly uses two different methods to calculate the rate of change of the magnetic field for this purpose. We show that there is a large difference between the two methods, and highlight certain situations where this difference is potentially significant.

By using magnetic field recordings sampled at 50 Hz by Swarm A and C satellites around the quasi-coplanar orbit configuration, near 1 October 2021, we investigate the properties of kilometer-scale field-aligned currents (FACs) at auroral latitudes. The kilometer-scale (0.2-5 km) FACs exhibit short-lived (<1 s) randomly appearing large current density spikes (partly exceeding 100 µA m-2). Preferred occurrences are the noon to prenoon (nightside to dusk) sector around 80° (70°) MLat, respectively.

The lack of ground observation instruments and the vast ocean coverage make the Southwest Indian Ocean (SWIO) region difficult to access and poorly studied. For gathering ground-based camera information, satellite measurements have been used with the primary goal of characterizing both sites Saint-Denis of Reunion Island and Antananarivo Madagascar in terms of cloudiness. This study shows the particularity of each site and enhances our understanding of cloud properties, particularly in the SWIO.

The magnetic mirror force bends the orbits of electrons precipitating into the atmosphere. It has been suggested that relativistic electrons make much less ionization due to the force than if it did not exist, but the actual effectivity in the atmospheric electron density has not been revealed. We used conjugated observational data from the ELFIN (Electron Losses and Fields INvestigation) satellite and the EISCAT (European Incoherent SCATter scientific radar system) Tromsø radar to find that the electron density decreased by about 40 % at 80 km altitude because of the force.

This study addresses the design of next-generation incoherent scatter radar experiments used to study the ionosphere, particularly with systems that have multiple sites. We have developed a method to estimate uncertainties of measurements of plasma density, temperature, and ion drift. Our method is open-source, and helps to optimize radar configurations and assess the effectiveness of an experiment. This method ultimately serves to enhance our understanding of Earth's space environment.

Analysis of 10 years of continuous measurements provided MMARIA/SIMONe Norway and MMARIA/SIMONe Germany reveals that the divergent and vortical motions in the mesosphere and lower thermosphere exchange the dominant role depending on the height and the time of the year. At summer mesopause altitudes over middle latitudes, the horizontal divergence and the relative vorticity contribute approximately the same, indicating an energetic balance between mesoscale divergent and vortical motions.