HENON (Heliospheric pioneer for solar and interplanetary threats defence) is a new European CubeSat technology demonstration mission conceived to address the widely recognized space weather need for longer lead-time measurements of the solar wind upstream of the Earth. To do this, HENON will occupy a distant retrograde orbit in the Sun-Earth system, ‘orbiting’ the Earth once per year and spending a significant period of time upstream of the Earth at 0.1 AU distance, x10 that of the L1 point. Planned for launch in early 2027, HENON will carry a miniaturised space weather payload as a pathfinder to demonstrate increased warning times for space weather conditions at Earth. This payload includes a radiation monitor, a solar wind instrument, and a magnetometer, MAGIC.In this contribution we present the MAGIC instrument that is being developed for HENON. MAGIC is highly miniaturised and based on magneto-resistive technology, making it a suitable instrument solution given the limited resource envelope on HENON. MAGIC’s flight heritage includes the CINEMA and RadCube CubeSats in low-Earth orbit, with a further version now delivered for flight as part of the ERSA payload planned for the Lunar Gateway. Here we describe the instrument concept and design, as well as the main technical developments arising from the implementation of MAGIC on HENON, most specifically in efforts to improve radiation hardness assurance.Although HENON is conceived in the context of space weather monitoring, by measuring the solar wind magnetic field HENON-MAGIC will help advance our understanding of the solar wind and heliophysics more generally. We review key outstanding scientific questions relating to the solar wind that HENON will provide insight into, and summarise some previous observations that help inform the HENON science goals.

Magnetic reconnection powers explosive releases of magnetic energy, heating and particle acceleration throughout the plasma universe. Knowledge of this universal process is vital to understanding the Heliosphere, as it plays a key role in solar flares, coronal mass ejections, coronal heating, solar wind acceleration, geomagnetic storms, and interactions between the solar wind and planetary magnetospheres. As such, reconnection underpins multiple science objectives of multiple future space missions. The UK plays a leading role in this international field, through a combination of in situ measurements from Earth's magnetosphere and the solar wind, observations of the solar corona and chromosphere, and world-class numerical simulations and theory. This white paper identifies: Nine priority science objectives for reconnection research in the next decade; Recommendations to guide investment in theory, simulations and infrastructure; Mission priorities and required measurements to ensure the UK maintains and improves its world-class credentials in reconnection science.

Magnetic reconnection is a fundamental process in astrophysical plasma, as it enables the dissipation of energy at kinetic scales as well as large-scale reconfiguration of the magnetic topology. In the solar wind, its quantitative role in plasma dynamics and particle energization remains an open question that is starting to come into focus as more missions now probe the inner heliosphere. To more efficiently detect magnetic reconnection in-situ using automated and modern methods is one of the challenges that can bring us closer to understanding the impact of magnetic reconnection on its surrounding magnetized environment. In this presentation, we make use of existing databases to focus on the evolution of magnetic reconnection properties through the heliosphere, using several space missions such as Parker Solar Probe (PSP), Solar Orbiter and Wind. We investigate the properties of small-scale reconnecting current sheets found in the turbulent solar wind as a function of radial distance and plasma source. In parallel, we also make use of PSP-Solar Orbiter alignments to study how the large-scale and high-shear reconnection occurring at the heliospheric current sheet evolves as it propagates in the solar wind. Finally, we emphasize how reconnection has a high impact on coherent structure evolution such as coronal mass ejection erosion or merging. Collectively, these results show that magnetic reconnection is ubiquitous in the solar wind and occurs in a wide variety of settings, with a high impact on its surrounding environment. We discuss how the recent growth of available in-situ spacecraft mission data inside the Earth orbit promises further substantial progress in our understanding of magnetic reconnection occurrence, properties and impact in the solar wind.

Magnetic reconnection is a fundamentally important process in space plasmas due to the release and repartition of the magnetic energy stored within the reconnecting field. As this energy transfer significantly impacts magnetospheric dynamics, understanding the partition of this energy and how this varies across the reconnection site can provide further insight into other magnetospheric processes. Although in situ spacecraft data provide direct measurements of relevant plasma properties, it can be difficult to establish the location of spacecraft relative to the reconnection site. This frustrates efforts to evaluate the way in which energy fluxes change with distance from the central reconnection X-line. Under certain circumstances, reconstruction techniques can be used to estimate the spacecraft trajectory through individual events, but these may rely on simplifying assumptions limiting their use. This motivates new approaches to determining where a spacecraft is relative to the reconnection structure. By utilising forefront machine learning techniques, we can more accurately study individual regions associated with the reconnection process and thus understand how they individually contribute to repartitioning the overall energy budget. In this context, we present these new applications of machine learning techniques to identify the regions in both simulation and spacecraft data. Firstly, we present the results of a robust method which utilises k-means clustering to identify different regions encountered within the overall reconnection X-line structure. This uses plasma fluid and field variables output by a 2.5-D PIC simulation with a geometry comparable to that of reconnection in Earth’s magnetotail. We then translate this model for use in spacecraft data by implementing an approach based on a recurrent neural network to account for the temporal context of the observations. We demonstrate the use of this model on MMS observations of reconnection in the Earth’s magnetotail, examining the properties of the plasma energy flux in different regions. We conclude by discussing how this approach may find use in other contexts where reconnection is observed in space plasmas.

In order to better safeguard society and infrastructure from space weather hazards, improved forecasting capabilities are required. To maximise the efficiency of mitigation strategies, forecasting products must not only be accurate, but also timely and tailored to end-user needs. For understanding and predicting the behaviour of the near-Earth space environment in changing solar wind conditions, physics-based modelling is extremely powerful, though often comes at considerable computational expense. The Bergen-Imperial Global Geospace (BIGG) project is an ongoing collaborative effort to provide new space weather forecasting capabilities to the ESA space weather service network via the use of two 3D magnetohydrodynamic (MHD) magnetosphere models, GorgonOps and the Space Weather Modelling Framework (SWMF). Solar wind observations as measured in situ at L1 will be continuously and automatically ingested as simulation inputs, with minimal human intervention. Both models have been optimised such that they are able to run in faster than real time, using only modest computational resources, delivering bespoke forecasting products to the end-user community via a web portal and API in a timely fashion. This multi-model approach will provide forecast diversity and redundancy to ensure continuous and reliable service provision to Europe and beyond.

Field-particle energy exchange is important to the magnetic reconnection process, but uncertainties regarding the time evolution of this exchange remain. We investigate the temporal dynamics of field-particle energy exchange during magnetic reconnection, using Magnetospheric Multiscale mission observations of an electron-only reconnection event in the magnetosheath. The electron energy is in local minimum at the x-line due to a density depletion, while the magnetic energy is in local maximum due to a guide field enhancement. The electromagnetic energy transport comes almost entirely from guide field contributions and is confined within the reconnection plane, while the most significant contribution to electron energy transport is independent of the drift velocity with additional out-of-plane signatures. Multi-spacecraft analysis suggests that the guide field energy is decreasing while the electron density is increasing, both evolving such that the system is moving toward a more uniform distribution of magnetic and thermal energy. The exchange of electromagnetic and thermal energy in collisionless plasmas is an important area of study to understand many space physics processes. The authors use in-situ, high resolution measurements from the MMS mission to examine the spatiotemporal evolution of the electron thermal and electromagnetic energy landscape during an encounter with a magnetic reconnection site in the Earth’s magnetosphere.

The electron diffusion region (EDR) is believed to be a key region for the conversion of energy associated with magnetic reconnection from magnetic to kinetic and thermal, but the nature of energy transport and conversion in EDRs is still not well understood. In this work, we capitalise on recent studies that have increased the number of referenced EDRs observed by MMS and perform a statistical study of 80 near X-line events previously identified in the literature. Upon detailed analysis, MMS was found to be located within the inner EDR for 45 of these events, while others correspond to outer EDR or IDR crossings.We investigate energy partition in their vicinity and find that the electron enthalpy flux dominates within the EDRs compared to the bulk kinetic and heat fluxes. We then evaluate the stationary terms of the energy conservation equation and find that large fluctuations of the electron enthalpy flux divergence tend to occur in the EDRs, suggestive of a complex energy transfer process dominated by the internal energy flux contribution. We also examine the possible role of magnetic shear/guide field, but this is somewhat limited by the fact that many events occur at relatively high shear and low guide field conditions. We conclude with considering how in future work, comparing these results to magnetotail- (symmetric) and magnetosheath- (low shear) EDR may bring further insight into how the regime in which magnetic reconnection occurs can impact the energy conversion and transport.

Magnetic reconnection is a ubiquitous plasma process that transforms magnetic energy into particle energy during eruptive events throughout the universe. Reconnection not only converts energy during solar flares and geomagnetic substorms that drive space weather near Earth, but it may also play critical roles in the high energy emissions from the magnetospheres of neutron stars and black holes. In this review article, we focus on collisionless plasmas that are most relevant to reconnection in many space and astrophysical plasmas. Guided by first-principles kinetic simulations and spaceborne in-situ observations, we highlight the most recent progress in understanding this fundamental plasma process. We start by discussing the non-ideal electric field in the generalized Ohm’s law that breaks the frozen-in flux condition in ideal magnetohydrodynamics and allows magnetic reconnection to occur. We point out that this same reconnection electric field also plays an important role in sustaining the current and pressure in the current sheet and then discuss the determination of its magnitude (i.e., the reconnection rate), based on force balance and energy conservation. This approach to determining the reconnection rate is applied to kinetic current sheets with a wide variety of magnetic geometries, parameters, and background conditions. We also briefly review the key diagnostics and modeling of energy conversion around the reconnection diffusion region, seeking insights from recently developed theories. Finally, future prospects and open questions are discussed.

Recent multi-point measurements, in particular from the Magnetospheric Multiscale (MMS) spacecraft, have advanced the understanding of micro-scale aspects of magnetic reconnection. In addition, the MMS mission, as part of the Heliospheric System Observatory, combined with recent advances in global magnetospheric modeling, have furthered the understanding of meso- and global-scale structure and consequences of reconnection. Magnetic reconnection at the dayside magnetopause and in the magnetotail are the drivers of the global Dungey cycle, a classical picture of global magnetospheric circulation. Some recent advances in the global structure and consequences of reconnection that are addressed here include a detailed understanding of the location and steadiness of reconnection at the dayside magnetopause, the importance of multiple plasma sources in the global circulation, and reconnection consequences in the magnetotail. These advances notwithstanding, there are important questions about global reconnection that remain. These questions focus on how multiple reconnection and reconnection variability fit into and complicate the Dungey Cycle picture of global magnetospheric circulation.

Severe space weather has the potential to cause significant socio‐economic impact and it is widely accepted that mitigating this risk requires more comprehensive observations of the Sun and heliosphere, enabling more accurate forecasting of significant events with longer lead‐times. In this context, it is now recognized that observations from the L5 Sun‐Earth Lagrange point (both remote and in situ) would offer considerable improvements in our ability to monitor and forecast space weather. Remote sensing from L5 allows for the observation of solar features earlier than at L1, providing early monitoring of active region development, as well as tracking of interplanetary coronal mass ejections through the inner heliosphere. In situ measurements at L5 characterize the solar wind's geoeffectiveness (particularly stream interaction regions), and can also be ingested into heliospheric models, improving their performance. The Vigil space weather mission is part of the ESA Space Safety Program and will provide a real‐time data stream for space weather services from L5 following its anticipated launch in the early 2030s. The interplanetary magnetic field is a key observational parameter, and here we describe the development of the Vigil magnetometer instrument for operational space weather monitoring at the L5 point. We summarize the baseline instrument capabilities, demonstrating how heritage from science missions has been leveraged to develop a low‐risk, high‐heritage instrument concept.

Understanding of Earth’s geomagnetic environment is critical to mitigating the space weather impacts caused by disruptive geoelectric fields in power lines and other conductors on Earth’s surface. These impacts are the result of a chain of processes driven by the solar wind and linking Earth’s magnetosphere, ionosphere, thermosphere and Earth’s surface. Tremendous progress has been made over the last two decades in understanding the solar wind driving mechanisms, the coupling mechanisms connecting the magnetically controlled regions of near-Earth space, and the impacts of these collective processes on human technologies on Earth’s surface. Studies of solar wind drivers have been focused on understanding the responses of the geomagnetic environment to spatial and temporal variations in the solar wind associated with Coronal Mass Ejections, Corotating Interaction Regions, Interplanetary Shocks, High-Speed Streams, and other interplanetary magnetic field structures. Increasingly sophisticated numerical models are able to simulate the magnetospheric response to the solar wind forcing associated with these structures. Magnetosphere-ionosphere-thermosphere coupling remains a great challenge, although new observations and sophisticated models that can assimilate disparate data sets have improved the ability to specify the electrodynamic properties of the high latitude ionosphere. The temporal and spatial resolution needed to predict the electric fields, conductivities, and currents in the ionosphere is driving the need for further advances. These parameters are intricately tied to auroral phenomena—energy deposition due to Joule heating and precipitating particles, motions of the auroral boundary, and ion outflow. A new view of these auroral processes is emerging that focuses on small-scale structures in the magnetosphere and their ionospheric effects, which may include the rapid variations in current associated with geomagnetically induced currents and the resulting perturbations to geoelectric fields on Earth’s surface. Improvements in model development have paralleled the advancements in understanding, yielding coupled models that better replicate the spatial and temporal scales needed to simulate the interconnected domains. Many realizations of such multi-component systems are under development, each with its own limitations and advantages. Challenges remain in the ability of models to quantify uncertainties introduced by propagation of solar wind parameters, to account for numerical effects in model codes, and to handle the special conditions occurring during extreme events. The impacts to technical systems on the ground are highly sensitive to the local electric properties of Earth’s surface, as well as to the specific technology at risk. Current research is focused on understanding the characteristics of geomagnetic disturbances that are important for geomagnetically induced currents, the development of earth conductivity models, the calculation of geoelectric fields, and the modeling of induced currents in the different affected systems. Assessing and mitigating the risks to technical systems requires quantitative knowledge of the range of values to be expected under all possible geomagnetic and technical conditions. Considering the progress that has been made in studying the chain of events leading to hazardous geomagnetic disturbances, the path forward will require concerted efforts to reveal missing physics, improve modeling capabilities, and deploy new observational assets. New understanding should be targeted to accurately quantify solar wind driving, magnetosphere-ionosphere-thermosphere coupling, and the impacts on specific technologies. The research, modeling, and observations highlighted here provide a framework for constructing a plan by which the international science community can comprehensively address the growing threat to human technologies caused by geomagnetic disturbances.

Magnetic reconnection is a fundamental plasma process which facilitates the conversion of magnetic energy to particle energies. This local process both contributes to and is affected by a larger system, being dependent on plasma conditions and transporting energy around the system, such as Earth's magnetosphere. When studying the reconnection process with in situ spacecraft data, it can be difficult to determine where spacecraft are in relation to the reconnection structure. In this work, we use k-means clustering, an unsupervised machine learning technique, to identify regions in a 2.5-D PIC simulation of symmetric magnetic reconnection with conditions comparable to those observed in Earth's magnetotail. This allows energy flux densities to be attributed to these regions. The ion enthalpy flux density is the most dominant form of energy flux density in the outflows, agreeing with previous studies. 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. The proportion of outflowing particle energy flux decreases as guide field increases. We find that k-means is beneficial for analyzing data and comparing between simulations and in situ data. 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.

The electron diffusion region (EDR) is a key region for magnetic reconnection, but the typical energy transport and conversion in EDRs is still not well understood. In this work, we perform a statistical study of 80 previously published near X-line events identified at the dayside magnetopause in Magnetospheric Multiscale data. We find 44 events that clearly present all commonly accepted EDR signatures and use this database to investigate energy flux partition and energy conversion. We find that energy partition is changed inside EDRs, with a 71%-29% allocation of particle energy flux density between electrons and ions respectively. The electron enthalpy flux density is found to dominate locally at all EDRs and is predominantly oriented in the out-of-plane direction, perpendicular to the reconnecting magnetic field. We also examine the transition from electron- to ion-dominated energy flux partition further from the EDR, finding this typically occurs at scales of the order of the ion inertial length, larger than the typical EDR size. We then investigate energy conversion and transport and highlight complex processes, with potential non-steady-state energy accumulation and release near the EDR. We discuss the implications of our results for reconnection energy conversion, and for magnetopause dynamics in general. Magnetic reconnection is a key plasma phenomenon that occurs in many astrophysical systems, such as in the atmosphere of stars and in the vicinity of magnetized planets like the Earth. It enables rapid conversion of energy as particles gain energy from the magnetic field and are accelerated and heated. In 2015, the 4-satellite Magnetospheric Multi-Scale (MMS) mission launched to specifically probe magnetic reconnection close to the Earth. Here we analyze MMS data, first reviewing all previously reported measurements of the very heart of the reconnection region by MMS, and cross-analyzing them to provide a catalog of 44 confirmed events. We use this catalog to understand how energy is changing during reconnection, finding that energy is mostly deposited to electrons at the heart of the reconnection region. The transport of thermal energy is most important there, and this energy is flowing out of the reconnection region in a direction transverse to the magnetic field. We find that the transfer of energy between field and particles is complex, with temporal effects at play near the reconnection region. These findings bring new insight into the physics of reconnection energetics and have wide implications for wherever reconnection is observed. We provide the first comparative statistical study of all previously reported MMS dayside magnetopause EDRs and confirm 44 clear encounters Energy flux partition changes at the EDR, it is locally dominated by the electron enthalpy flux oriented in the out-of-plane direction We highlight complex field-particle energy exchange near the EDR where temporal and non linear effects seem play a role

The Kelvin-Helmholtz Instability (KHI), arising from velocity shear across the magnetopause, plays a significant role in the viscous-like transfer of mass, momentum, and energy from the shocked solar wind into the magnetosphere. While the KHI leads to growth of surface waves and vortices, suitable detection methods for these applicable to magnetohydrodynamics (MHD) are currently lacking. A novel method is derived based on the well-established λ-family of hydrodynamic vortex identification techniques, which define a vortex as a local minimum in an adapted pressure field. The J×B Lorentz force is incorporated into this method by using an effective total pressure in MHD, including both magnetic pressure and a pressure-like part of the magnetic tension derived from a Helmholtz decomposition. The λMHD method is shown to comprise of four physical effects: vortical momentum, density gradients, fluid compressibility, and the rotational part of the magnetic tension. A local three-dimensional MHD simulation representative of near-flank magnetopause conditions (plasma β’s 0.5–5 and convective Mach numbers Mf∼0.4) under northward interplanetary magnetic field (IMF) is used to validate λMHD. Analysis shows it correlates well with hydrodynamic vortex definitions, though the level of correlation decreases with vortex evolution. Overall, vortical momentum dominates λMHD at all times. During the linear growth phase, density gradients act to oppose vortex formation. By the highly nonlinear stage, the formation of small-scale structures leads to a rising importance of the magnetic tension. Compressibility was found to be insignificant throughout. Finally, a demonstration of this method adapted to tetrahedral spacecraft observations is performed.

The HEliospheric pioNeer for sOlar and interplanetary threats defeNce (HENON) is a new mission concept conceived to address the widely recognized need to make a leap forward in the Space Weather (SWE) forecasting and science. The HENON baseline foresees one 12U CubeSat orbiting along a Distant Retrograde Orbit (DRO) of the Sun-Earth system, so that the HENON CubeSat will stay for a long period of time very far upstream of the Earth (well beyond L1 at least ~ 0.1 AU). HENON will embark a state of the art radiation monitor, which will provide high-resolution measurements of energetic particle spectra, making HENON the first mission ever providing a real time monitoring of the particle radiation environment in the deep space. This will enable the insight into the near-Earth spatial variations of SEP events giving rise to better boundary conditions for forecasting and nowcasting tools. The HENON mission also aims to embark payloads tailored for SWE observations, in order to pave the way for a significant improvement (several hours) of the forecasting horizons of geo-effective interplanetary structures (ICMEs, HSSs). HENON has important technological objectives including demonstration of the capability of the CubeSat technologies in deep space to reach both scientific and operational goals through the first ever operation in unexplored DRO orbits, thus paving the way for a future fleet of such CubeSats equally spaced along the DRO, which could provide continuous near real-time measurements for space weather forecasting. HENON is in the A/B study phase that is being developed in the framework of the ESA General Support Technology Program (GSTP). HENON is funded by the Italian Space Agency as part of the ALCOR programme.

A new Roadmap for Solar System Research in the UK has been published, and the Solar System Advisory Panel report on the processes involved in updating the previous iteration

EDITORIAL article Front. Astron. Space Sci., 19 July 2023Sec. Space Physics Volume 10 - 2023 | https://doi.org/10.3389/fspas.2023.1254235

Various physical processes in association with magnetic reconnection occur over multiple scales from the microscopic to macroscopic scale lengths. This paper reviews multi-scale and cross-scale aspects of magnetic reconnection revealed in the near-Earth space beyond the general global-scale features and magnetospheric circulation organized by the Dungey Cycle. Significant and novel advancements recently reported, in particular, since the launch of the Magnetospheric Multi-scale mission (MMS), are highlighted being categorized into different locations with different magnetic topologies. These potentially paradigm-shifting findings include shock and foreshock transient driven reconnection, magnetosheath turbulent reconnection, flow shear driven reconnection, multiple X-line structures generated in the dayside/flankside/nightside magnetospheric current sheets, development and evolution of reconnection-driven structures such as flux transfer events, flux ropes, and dipolarization fronts, and their interactions with ambient plasmas. The paper emphasizes key aspects of kinetic processes leading to multi-scale structures and bringing large-scale impacts of magnetic reconnection as discovered in the geospace environment. These key features can be relevant and applicable to understanding other heliospheric and astrophysical systems.

Auroral zones are regions where, in an average sense, aurorae due to solar activity are most likely spotted. Their shape and, similarly, the geographical locations most vulnerable to extreme space weather events (which we term ‘danger zones’) are modulated by Earth’s time-dependent internal magnetic field whose structure changes on yearly to decadal timescales. Strategies for mitigating ground-based space weather impacts over the next few decades can benefit from accurate forecasts of this evolution. Existing auroral zone forecasts use simplified assumptions of geomagnetic field variations. By harnessing the capability of modern geomagnetic field forecasts based on the dynamics of Earth’s core we estimate the evolution of the auroral zones and of the danger zones over the next 50 years. Our results predict that space-weather related risk will not change significantly in Europe, Australia and New Zealand. Mid-to-high latitude cities such as Edinburgh, Copenhagen and Dunedin will remain in high-risk regions. However, northward change of the auroral and danger zones over North America will likely cause urban centres such as Edmonton and Labrador City to be exposed by 2070 to the potential impact of severe solar activity.