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Journal articleDavies EE, Weiler E, M枚stl C, et al., 2026, , Space Weather, Vol: 24
We present the first real-time predictions of coronal mass ejection (CME) magnetic structure and resulting geomagnetic impact at Earth for two events using far-upstream observations from Solar Orbiter during March 2024. While our approach assumes idealized conditions for CME propagation and scaling, in situ magnetic field data from upstream monitors still produced realistic predictions despite the large heliocentric distance between Solar Orbiter and L1 (0.53 and 0.60 au). Geomagnetic index predictions were made 15.3 and 4.3 hr before the CME shock arrival at L1, and 33.9 and 10.3 hr ahead of peak storm time; a large improvement over current L1-based nowcasting capabilities. We find that observationally constraining the simple drag-based models using the upstream in situ observations improved arrival time estimates for the two events in this study, although arrival time errors of several hours still remain. Our results show that good predictions of CME magnetic structure and geomagnetic indices with actionable lead-times can be made with far upstream spacecraft, even with longitudinal separations up to 10 (Formula presented.) from the Sun-Earth line, over heliocentric distance ranges where radial evolution effects dominate over longitudinal effects. Limitations include different expansion behaviors for individual CMEs and regions within. Future missions providing continuous data, including solar wind plasma parameters alongside magnetic field measurements, could account for preexisting disturbed conditions and improve geomagnetic prediction accuracy. Our findings demonstrate the substantial value of real-time upstream solar wind measurements for enhancing geomagnetic forecasting accuracy at Earth and provide critical validation for future dedicated upstream space weather missions.
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Journal articleMallet A, Shi C, Tenerani A, et al., 2026, , Space Science Reviews, Vol: 222, ISSN: 0038-6308
Magnetic switchbacks are large-amplitude fluctuations in the interplanetary magnetic field, and appear frequently in the near-Sun solar wind explored recently by Parker Solar Probe: these new observations have prompted many new studies into their properties and origins. Here, we first review what is known about how switchbacks evolve as they travel away from the Sun: both in terms of their expansion-driven growth and their decay due to various processes like turbulence, reconnection, dispersion, parametric instability, and interaction with interplanetary shocks. We then review the current state of knowledge on how switchbacks impact the physics of the solar wind as a whole: in terms of the turbulent cascade, acceleration and heating of the wind, modification of the open solar flux and scattering of energetic particles. Finally, we suggest future studies to further our understanding of switchback evolution and impacts on the heliosphere.
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Journal articleYousuf F, Li Z, Bale SD, et al., 2026, , Astronomical Journal, Vol: 172, ISSN: 0004-6256
The Lunar Surface Electromagnetics Experiment (LuSEE-Night) is a joint NASA-DOE-ESA low-frequency radio telescope that will reach the lunar far side in 2027. The unknown dielectric properties of the subsurface at the LuSEE-Night landing site impose the most significant limitation for precision instrument calibration, as reflections from the lunar subsurface can change the primary beam at the 10%–20% level. Simulations of these effects have provided insight and concern, showing that the lunar subsurface modeled as a lossy dielectric can absorb a large amount of the power of the sky signal. While this absorption may not strongly impact the signal-to-noise ratio in a sky noise-dominated regime, it could complicate the beam pattern and make the signal more difficult to model and interpret. We have simulated the far-field properties of the LuSEE-Night beam for varying dielectric profiles of the lunar subsurface. We find that varying the properties of the lunar subsurface has the most significant impact around the antenna resonance, impacting its amplitude, position, and width. Conversely, changing the properties of the foreground impacts the data across the band. We use a Bayesian inference pipeline to jointly estimate parameters of a Galactic foreground model and dielectric properties of the lunar subsurface around the LuSEE-Night landing site and find that parameters of both the galaxy and subsurface properties can be estimated jointly. While the modeling is somewhat idealized, we believe that the results are largely robust owing to the fact that spectral variations for plausible subsurface and galaxy models have very different spectral signatures.
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Journal articleLazzeri C, Forsyth C, Samsonov A, et al., 2026, , Journal of Geophysical Research: Space Physics, Vol: 131, ISSN: 2169-9380
We present a case study of large amplitude, compressional Pc5 waves observed by GOES 13 and 15 at geosynchronous orbit near noon. These waves were excited near the arrival time of two consecutive solar wind dynamic pressure spikes at the magnetopause, the second of which was associated with a large and rapid southward turning of the Interplanetary Magnetic Field (IMF). Magnetopause oscillations at a similar frequency were observed by the THEMIS spacecraft in the post-noon magnetosphere, however without clear signatures of compressional waves. The analysis of the ground response near the GOES foot-points, located close to the Churchill line of magnetometer stations, revealed an increase in wave power following each spike, with slight changes in polarizations. Following the second pressure spike's arrival at the magnetosphere, we found evidence of Field Line Resonances in the Northward component of the magnetic field, which suggests coupling with the compressional waves observed at GOES. We investigated potential Ultra Low Frequency drivers, and identified the most likely driving mechanism to be the drift-mirror instability; lack of appropriate measurements however prevented us from confirming this hypothesis.
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Journal articleGrimmich N, Constantinescu OD, Auster HU, et al., 2026, , Journal of Geophysical Research Space Physics, Vol: 131, ISSN: 2169-9380
During their 24 years mission of investigating the Earth's magnetosphere, the four Cluster satellites delivered high quality magnetic field data measured by the onboard fluxgate magnetometers (FGM). To achieve the accuracy required for scientific studies, the raw magnetic field data need to be calibrated on a regular basis. The calibration effort has been shared between the FGM team at the TU Braunschweig which performed the initial daily calibration necessary for the quick access to calibrated magnetic field data, and the FGM team at the Imperia(ICL) which performed the final calibration of the data. This work focusses on the in-flight daily calibration, the final calibration results are discussed in this issue in a complementary paper prepared by the ICL team. We provide a brief overview of the methods employed for the daily calibration, present a statistical analysis of the daily calibration parameters and investigate their long-term trends and their dependence on temperature.
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Journal articleMarjani S, Mehrdad S, Quaas J, 2026, , Atmospheric Chemistry and Physics, Vol: 26, Pages: 10695-10725, ISSN: 1680-7316
Persistent contrails are a major contributor to aviation-induced non-CO<inf>2</inf> climate forcing, yet the extent to which their development depends on background cloud properties remains unclear. In this study, we aim to investigate persistent contrail development in various cloudy backgrounds. We use the high-resolution ICON-LEM model with a horizontal resolution of 154 m. Eight distinct ice-cloud scenarios are simulated as control runs, each initialized with realistic meteorological forcing. For each control case, a corresponding perturbation run is conducted by introducing an identical contrail, allowing us to assess its evolution within the same cloudy, ice-supersaturated environment. We find that persistent contrails embedded within natural cirrus clouds not only survive but can also alter the humidity field, cloud microphysics, and potentially the radiative properties of the host cloud. The evolution of persistent contrails is highly sensitive to the microphysical and thermodynamic properties of the background ice-supersaturated regions, particularly the combination of supersaturated layer thickness below flight level and the temporal availability of excess water vapor, as the former alone is not sufficient to sustain contrail development. Although vertical growth through fall streaks is commonly expected, we suggest that in regions of high ice supersaturation and low atmospheric stability, contrails may also expand above the flight height due to latent heat release from deposition. Our findings indicate that threshold criteria alone are insufficient to predict the growth and climate relevance of persistent contrails, because time-varying background cloud and humidity conditions strongly influence how far contrails develop.
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Journal articleEastwood J, Archer M, Waters C, et al., 2026, , Scientific Reports, ISSN: 2045-2322
Geomagnetic storms are a key driver of space weather impacts. The enhancement of ionospheric currents during these events can produce geomagnetically induced currents (GICs) that may interfere with the operation of ground infrastructure such as power grids, pipelines, and railway networks. It is therefore critical to understand how, why, and when very intense GICs may occur during an extended geomagnetic storm interval. Supersubstorms are extremely intense substorms which may occur during the main or recovery phases of geomagnetic storms. These rare events bear special investigation because they may have a significant impact on GIC formation during extreme geomagnetic storms. Multiple supersubstorms were observed during the May 2024 geomagnetic storm, and here we report new observations of supersubstorm field aligned currents (FACs), observed in situ by the MAGnetometer from ImperiaCollege (MAGIC) instrument on the RadCube technology demonstration CubeSat. These measurements provide new insight into the detailed structure of supersubstorm FACs, complementing global FAC maps, and reveal an extended spatial region containing magnetic fluctuations across a broad range of spatial/temporal scales, including intense localised current spikes. As well as revealing new details about supersubstorm-related FACs, these observations illustrate the need for dense constellations of low-Earth-orbit satellite-based magnetometers for space weather monitoring.
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Journal articleZelinka MD, Myers TA, Qin Y, et al., 2026, , Communications Earth & Environment, Vol: 7, ISSN: 2662-4435
Earth’s energy imbalance has increased markedly over the past two decades, reaching a record in 2023. Both the long-term trend and year-to-year variations are linked to reduced reflection of sunlight by low-level clouds, which is pronounced over Northern Hemisphere oceans. However, the causes of these cloud changes and their implications for future Earth system evolution are unknown, raising concerns about a stronger-than-expected cloud feedback. Here we quantify the meteorological factors behind interannual cloud-radiative anomalies, several of which aligned to produce the extreme 2023 value. These meteorological variations are superposed on a background of declining sulfate aerosol concentrations, contributing to a sustained decrease in cloud reflection over the past 22 years. The resulting constraints on cloud feedback and aerosol forcing are consistent with previous studies, supporting an equilibrium climate sensitivity near 3鈭楥 (likely range 2.7–4.1鈭楥). Thus, recent observations do not indicate an emerging stronger cloud feedback or underestimated future warming.
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Journal articleDakeyo JB, Ervin T, Bale S, et al., 2026, , Astrophysical Journal, Vol: 1006, ISSN: 0004-637X
The properties of the solar wind, as measured in situ throughout the heliosphere, depend both on the characteristics of its coronal source and on the intrinsic processes governing its interplanetary evolution. Recently, radial and Parker spiral alignment techniques have been applied to Parker Solar Probe (PSP) and Solar Orbiter (SO) observations to investigate the radial evolution of the same solar wind parcel. These studies have shown that the solar wind can undergo significant acceleration even beyond its primary acceleration region (i.e., above 15 R<inf>鈯</inf>). However, such radial and Parker spiral alignments are rare in practice, which limits the statistical significance and general applicability of the results. We introduce a new source alignment technique designed to overcome these limitations. Using magnetic backmapping, we associate similar solar wind streams observed by the two spacecraft based on the proximity of their photospheric footpoints, combined with additional in situ stream similarity criteria. Applying the source alignment method to PSP and SO observations, we identify a total of 548 alignment intervals, each lasting 30 minutes. By constructing statistics over all alignments, we find that the solar wind speed increases by an average of 45% per radial decade (approximately 147 km s<sup>−1</sup>) between the two probes. This result demonstrates that solar wind acceleration in the inner heliosphere remains significant compared to that occurring below 15 R<inf>鈯</inf>. Among the different studied plasma parameters, the radial evolution of the electron temperature and plasma density shows the strongest anticorrelation with the increase in bulk velocity.
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Journal articleManolis AA, Manolis TA, Vouliotis A, et al., 2026, , Curr Vasc Pharmacol
Pericarditis is a common disease caused by various factors such as viral infections, systemic diseases, or drugs. A diagnosis of pericarditis is rendered in up to 5% of Emergency Room (ER) visits for non-ischemic chest pain. It is diagnosed when pleuritic chest pain is present, accentuated in the supine position, accompanied by ECG changes comprising new extensive ST-segment elevation and PR depression, a pericardial friction rub, and new or increased pericardial effusion on echocardiography. In North America and Western Europe, the most common causes of acute pericarditis are idiopathic or viral, followed by post-procedural (iatrogenic) pericarditis, radiation therapy, and cardiac surgery. Tuberculosis is the most common cause of pericarditis in endemic areas and is managed with antituberculosis therapy, with corticosteroids used when there is concurrent constrictive pericarditis. New diagnostic techniques have aided the sampling and analysis of pericardial fluid and in determining its cause. Treatment of pericarditis comprises high-dose Non-Steroidal AntiInflammatory Drugs (NSAIDs) for uncomplicated cases, with doses tapered when symptoms have subsided and C-reactive protein level has normalized, typically over several weeks. Colchicine (often a 3-6-month course) is needed to both alleviate symptoms and decrease recurrences, while glucocorticoids and newer therapies with interleukin-1 blockers are reserved for recurrences and/or failures of prior therapies. Integrated use of new imaging methods facilitates more precise detection and better management of complications such as pericardial effusion or constriction. The diagnostic yield of extensive laboratory evaluation and pericardiocentesis remains low; hence, invasive procedures should be limited mostly to patients in whom a therapeutic intervention is needed. The majority of pericardial effusions can be safely drained with an echo-guided percutaneous technique. Pericardiectomy remains the definitive treatment for
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Journal articleFredericks L, Rugenstein M, Thompson DWJ, et al., 2026, , Journal of Climate, Vol: 39, Pages: 4101-4116, ISSN: 0894-8755
Over the past decade, it has become clear that the radiative response to surface temperature change depends on the spatially varying structure in the temperature field, a phenomenon known as the “pattern effect.” The pattern effect is commonly estimated from dedicated climate model simulations forced with local surface temperature patches (Green’s function experiments). Green’s function experiments capture causal influences from temperature perturbations but are computationally expensive to run. Recently, however, several methods have been proposed that estimate the pattern effect through statistical means. These methods can accurately predict the radiative response to temperature variations in climate model simulations. The goal of this paper is to compare methods used to quantify the pattern effect. We apply each method to the same prediction task and discuss its advantages and disadvantages. Most methods indicate large negative feedbacks over the western Pacific. Over other regions, the methods frequently disagree on feedback sign and spatial homogeneity. While all methods yield similar predictions of the global radiative response to surface temperature variations driven by internal variability, they produce very different predictions from the patterns of surface temperature change in simulations forced with increasing carbon dioxide (CO2) concentrations. We discuss reasons for the discrepancies between methods and recommend paths toward using them in the future to enhance physical understanding of the pattern effect.
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Journal articlePugsley G, Gryspeerdt E, Nair V, 2026, , Proc Natl Acad Sci U S A, Vol: 123
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Journal articleBurne S, Boscoboinik G, Bertucci C, et al., 2026, , The Astrophysical Journal, Vol: 1005, ISSN: 0004-637X
The interaction between the supermagnetosonic solar wind and the atmosphere of the weakly magnetized planet Mars forms an induced magnetosphere preceded by a magnetic pileup boundary (MPB) and bow shock (BS). In situ measurements have shown that these boundaries are permanent and well-defined structures that exhibit significant variability driven by external (Sun, solar wind) and internal (planetary) factors. In this work, we used MAVEN observations from 2014 to 2019 to analyze the coupled behavior of the BS and MPB, focusing on their spatial correlation and variability under varying conditions. We examine contiguous BS-MPB spacecraft crossings and the magnetosheath region between them, and we explore the effects of various plasma parameters on the relative position of the boundaries and the thickness of the magnetosheath. We demonstrate a statistical correlation between the BS and MPB positions across multiple timescales, including sustained local solar wind and planetary conditions, seasonal changes, and solar cycle variations. These results support the interpretation that the MPB plays a key role as an electromagnetic obstacle to the solar wind, effectively controlling the formation of the bow shock. We also confirm the limited size of the Martian magnetosheath, both in absolute terms and relative to fundamental plasma scales, which has important implications for understanding the microscopic plasma processes responsible for solar wind thermalization. While acknowledging the limitations of single-spacecraft measurements, this study provides a foundation for future multipoint probing of the Martian environment and the magnetosphere as a system.
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Journal articleAuestad H, Shibu A, Ceppi P, et al., 2026, , npj Climate and Atmospheric Science, Vol: 9, ISSN: 2397-3722
Extratropical storms release latent heat as they transport warm, moist air poleward and upward. That latent heating feeds back on storms by intensifying individual cyclones and by altering the environmental conditions for the growth of storms, constituting a latent heating-dynamics feedback. As the climate warms, storm-track latent heating increases, but the role of this feedback in a future climate remains unclear. Using atmospheric general-circulation model experiments that separate the coupled heating-dynamics feedback from climatological changes in latent heating, we show that this feedback plays a leading-order role in intensifying storm tracks under +4 K warming. The feedback increases lower-tropospheric storm intensity, compensating for reduced baroclinicity, while its upper-tropospheric effect is seasonal: amplifying summer eddies but damping winter ones. The feedback is critical for storms that grow in moist environments, typical for summer and warmer climates, underscoring the need for accurate representation of moist processes in climate models.
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Journal articleKr盲mer E, Fatemi S, Gunell H, et al., 2026, , Monthly Notices of the Royal Astronomical Society, Vol: 550, ISSN: 0035-8711
<jats:title>ABSTRACT</jats:title> <jats:p>The magnetopause marks the boundary where the pressure of the magnetosheath balances the magnetic pressure of Earth’s magnetic field. Localized increases in magnetosheath pressure can therefore displace the magnetopause. One known plasma structure that exhibits such a local pressure increase is magnetosheath jets defined as transient dynamic pressure enhancements. These jets are particularly prominent downstream of the quasi-parallel bow shock, where they frequently interact with the magnetopause. To investigate the spatial and temporal characteristics of these interactions, we employ the 3D hybrid-kinetic plasma model Amitis with a steady plasma inflow. Our results show that jets downstream of the quasi-parallel bow shock can generate magnetopause surface waves that propagate flankward. Interestingly, while jets appear to have a similar velocity as the surface waves and continuously drive them, the jets’ apparent flankward motion does not align with the ion bulk velocity measured within the jets. This discrepancy may suggest ongoing jet generation at the bow shock, potentially linked to foreshock compressive structures.</jats:p>
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Journal articleHartinger MD, Shi X, Verkhoglyadova O, et al., 2026, , Journal of Geophysical Research: Space Physics, Vol: 131, ISSN: 2169-9380
<jats:title>Abstract</jats:title> <jats:p> Ionospheric Total Electron Content disturbances (dTEC) in the Ultra Low Frequency (ULF, timescales 10 min) range can be driven from below by processes at Earth's surface and lower atmosphere and from above by magnetospheric processes. Using magnetospheric satellite magnetometer, ground鈥恇ased magnetometer, and dTEC measurements in the auroral zone, Hartinger et al. (2025), <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.1029/2024ja033456">https://doi.org/10.1029/2024ja033456</jats:ext-link> showed that over much of the Pc3鈥5 band (∼2–50 mHz) ULF waves routinely drive dTEC perturbations correlated with magnetic field disturbances (dBground), suggesting dTEC could be used as a ULF wave diagnostic. Motivated by the significant differences expected for magnetosphere, ionosphere, atmosphere, and ground properties at a different latitude, we extend Hartinger et al. (2025), <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.1029/2024ja033456">https://doi.org/10.1029/2024ja033456</jats:ext-link> to examine mid鈥恖atitude ( degrees magnetic latitude) dTEC during conjunctions with the Van Allen Probes satellites, a ground magnetometer, and a Global Navigation Satellite System receiver. Consistent with the auroral zone, we find that dTEC often has a corresponding dBground signature, and that dTEC and dBground are well correlated with results dependent on the component of the magnetic field. We also find that dTEC amplitudes are lower (0.5 TECU) and tend to occur at higher frequencies than in the auroral zone, as expected for magnetospheric Pc3鈥5 wave latitude dependence. In contrast to the auroral zone, we find that dTEC power does not have
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Journal articleDasgupta B, Pandey S, Houweling S, et al., 2026, , Atmospheric Chemistry and Physics, Vol: 26, Pages: 8601-8616
<jats:p> Methane (CH <jats:sub>4</jats:sub> ) is a potent greenhouse gas; however, the causes of its growth since 2006 are a subject of debate. While measurements of CH <jats:sub>4</jats:sub> mole fraction and carbon isotopic composition ( <jats:italic>δ</jats:italic> <jats:sup>13</jats:sup> C-CH <jats:sub>4</jats:sub> ) have been extensively used to investigate the global CH <jats:sub>4</jats:sub> budget, the hydrogen isotopic composition ( <jats:italic>δ</jats:italic> D-CH <jats:sub>4</jats:sub> ) remains underutilised despite its unique sensitivity to source types and oxidation processes. Here, we assimilate a newly harmonised 35-year dataset of dual isotope measurements from high-latitude monitoring stations in both hemispheres within a two-box Bayesian inversion to quantify global CH <jats:sub>4</jats:sub> sources and sinks. The model integrates prior emissions from five source categories based on global bottom-up inventories. Methane removal processes are represented by sink-specific kinetic isotope effects as tropospheric and stratospheric loss, and soil uptake. We find that the inclusion of <jats:italic>δ</jats:italic> D-CH <jats:sub>4</jats:sub> improves the model's ability to constrain emission apportionment between biogenic and thermogenic sources, particularly for fossil fuel emissions during the late 1990s and early 2000s, which affects CH <jats:sub>4</jats:sub&g
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Journal articleTeixeira JCM, Burton C, Kelley DI, et al., 2026, , Earth System Dynamics, Vol: 17, Pages: 739-767, ISSN: 2190-4979
Fire schemes within Earth System Models capture long-term historical trends in burnt area, but they struggle to reproduce the pronounced decline observed over the past two decades. This study investigates whether the observed decline in global burnt area during 1998–2016 can be better represented in the JULES-INFERNO fire model by introducing a globally uniform dependence on the Human Development Index (HDI) as a proxy for socio-economic fire controls. This approach substantially reduces regional biases in annual burned area. In Temperate North America, model bias decreases from +735.57 % to +44.46 %, with similarly large reductions in Central America, Southern Hemisphere South America, Europe, and the Middle East. HDI also improves the representation of burned area trends in eight of the 14 GFED4s regions with significant negative trends in observations. However, correcting large positive regional biases removes compensating errors in the original model, leading to a stronger global negative bias, which shifts from −34.35 Mha in JULES-INFERNO to approximately −111 Mha in JULES-INFERNO with the HDI implementation. Overall, while HDI improves regional performance and better captures observed downward trends in some regions, it also reduces interannual variability and underestimates larger fires. This highlights both the potential and limitations of representing socio-economic influences within fire models using a simplified globally uniform formulation.
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Journal articleManolis AS, Manolis AA, Manolis TA, et al., 2026, , Curr Vasc Pharmacol
Work is a social determinant of Cardiovascular (CV) and general health and can both influence and be influenced by health. The type of work, working conditions, and work environment are fundamental social determinants of CV and general health status. Climate change presents an urgent and increasing threat to workers' health, via both direct exposure to environmental risks and the indirect worsening of social and health inequalities. Occupational health, which focuses on the promotion of mental and physical health and well-being of workers, and the avoidance of occupationrelated health risks, is a crucial but less discussed concern and component of human health. Relevant research at the intersection of climate change and occupational health remains scarce. Additionally, mitigation of climate change and adaptation efforts are driving forces for rapid transformations in the workplace, including shifts towards sustainability and circular economy models. These transitions are creating new occupational hazards, including those concerning renewable energy and the circular economy sectors. Investment in occupational health research and surveillance should be increased to address the evolving influences of both climate change and the green transition, to enhance and protect workers' CV and general health. Among the work-related factors that play an important role in patients with CVD, the following seem crucial: work participation, physical and mental work capability, appropriate work, support from and flexibility of the work environment, inter-personal communication, person-centered milieu, and interdisciplinary communication. A moderate leisure-time physical activity combined with moderate occupational physical activity may be a more plausible way to combine these two activities to sustain and/or improve CV health. Such an approach may be able to ameliorate workrelated outcomes in patients with CVD. Finally, lifestyle interventions targeting multiple behaviors are also mos
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Journal articleDong Y, Lu K, Hwang Y-T, et al., 2026, , Science Advances, Vol: 12, ISSN: 2375-2548
Observed sea-surface temperature (SST) trends over recent decades feature cooling in the tropical eastern Pacific and the Southern Ocean (SO). Growing evidence suggests that tropical cooling may partly stem from remote impacts of the SO. Using a hierarchy of multimodel simulations, we demonstrate that these teleconnections are robustly modulated by the mean-state intertropical convergence zone (ITCZ): Models with a more realistic ITCZ simulate a stronger tropical SST response to SO forcing via stronger wind-evaporation-SST feedback. When realistic Antarctic meltwater forcing is included, correcting a model’s tropical mean-state bias yields a stronger tropical cooling response to meltwater-driven SO cooling, improving the agreement between simulated and observed SST trends. Our results suggest that the SO’s contribution to tropical warming patterns is systematically underestimated due to model mean-state biases. Improving representations of the mean-state climate is therefore critical for accurately assessing large-scale climate responses associated with historical and future warming patterns.
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Journal articleMitchell DG, Lario D, Raouafi NE, et al., 2026, , Astrophysical Journal, Vol: 1003, ISSN: 0004-637X
Parker Solar Probe (PSP) observations of a small dispersive event on 2024 April 1 reveal highly enriched <sup>3</sup>He abundance in the suprathermal energy range (40–250 keV nucleon<sup>−1</sup>). Time dispersion observed in this impulsive solar energetic particle (SEP) event is consistent with an estimated onset time of 22:50 UT on 2024 March 31. The event occurred during an orbital segment as PSP moved from about 27 R<inf>s</inf> to about 29 R<inf>s</inf> while outbound in orbit 19. For this segment of the orbit, PSP’s motion in Carrington coordinates remains within about 1° of the same Carrington longitude. The <sup>3</sup>He content is much larger than the usual SEP abundances, especially in this energy range. Additionally, the <sup>3</sup>He energy spectrum is not power law in shape, unlike the H and <sup>4</sup>He spectra. Heavy ions (O, Fe) are also somewhat enhanced. These compositional signatures suggest that this is an example of resonant wave–particle acceleration, as hypothesized for generating the suprathermal seed particles required to account for the enrichment of various species above solar abundances in shock (or compression) acceleration models of SEP events. Like many previously reported impulsive <sup>3</sup>He-rich events, this event is associated with an energetic electron beam, type III radio emission, and a hard X-ray flare. However, associating the hard X-ray event with this SEP event requires significant (∼60°) prompt longitudinal propagation of energetic particles in the low corona before they access open magnetic flux, complicating its interpretation as part of the source process for this particular event.
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Journal articleWyper PF, Squire J, Pariat E, et al., 2026, , Space Science Reviews, Vol: 222, ISSN: 0038-6308
Magnetic switchbacks are large amplitude deflections of the magnetic field within the solar wind. They are Alfvénic in character and so are associated with a spike in velocity and a generally small variation in local plasma density. Early orbits of Parker Solar Probe revealed that the solar wind near the Sun is dominated by these structures, and therefore, they may be playing an important role in the energy budget and acceleration of the young solar wind. In this review, we present an overview of different mechanisms that have been proposed for how switchbacks could be formed. We group the mechanisms by whether they predominantly act in the low solar atmosphere or within the solar wind (in situ). We focus on mechanisms that can create reversals of the ambient magnetic field direction and, thus, account for the most extreme perturbations. The general consensus is that mechanisms in the lower solar atmosphere do not form such reversals on their own but provide the seed perturbations, flows, or particle beams necessary for in situ mechanisms to create switchbacks within the solar wind. Switchback observations thus likely contain an imprint of the coronal source of the seed perturbation or flow, which is evolved further locally by one of several plausible in situ mechanisms. We discuss the strengths and weaknesses of each mechanism and outline future observational and theoretical tests that could help differentiate between them.
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Journal articleSun W, Phan T, Huang J, et al., 2026, , Astrophysical Journal Letters, Vol: 1003, ISSN: 2041-8205
Magnetic reconnection is a fundamental physical process that can drive rapid conversion of magnetic energy into plasma bulk flows, thermal heating, and particle acceleration in space and astrophysical plasmas. Classical reconnection theory predicts that the Alfvénic reconnection exhausts are bounded by pairs of slow-mode shocks. However, identifying and characterizing these shocks through in situ spacecraft observations remains a challenge. Here, we report Parker Solar Probe observations of a reconnection exhaust embedded in the heliospheric current sheet at a heliocentric distance of 12.2 (Formula presented) R猕. The reconnection exhaust is bounded on both boundaries by compound magnetic structures rather than a pair of pure slow shocks. Each boundary consists of a rapidly evolving, steep, inner slow shock, whose Mach numbers and shock-normal angles change significantly within several minutes, and an outer, gradual compound structure that comprises a slow shock and a rotational discontinuity. These slow shocks are quasi-perpendicular and are accompanied by enhanced proton perpendicular heating. Deep within the reconnection exhaust, high perpendicular temperature together with large plasma (Formula presented) β trigger mirror instability and generate mirror-mode structures. These observations provide new insights into the structure of reconnection exhaust boundaries and their role in energy conversion in the near-Sun plasma.
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Journal articleAlconcel L, Brown P, Oddy T, et al., 2026, , Journal of Geophysical Research: Space Physics, Vol: 131, ISSN: 2169-9380
The calibration parameters of the Cluster mission's fluxgate magnetometer instruments have beendetermined and updated on a per鈥恛rbit basis throughout the 24 years of the mission. Since there is no absolute field reference for vector measurements in鈥恌light, various spacecraft鈥恡o鈥恠pacecraft and instrument鈥恡o鈥恑nstrument comparisons have been used to assess the accuracy of the measurements. Relative accuracy—consistency of the FGM measurements between spacecraft—is typically1%forfields up to 4,000nT,whichcoversmostof the key scientific regions visited by the Cluster spacecraft. Absolute accuracy is harder to quantify but may be as good as 2% over the same range. An analysis of long鈥恡erm trends in the calibration parameters shows variations on annual and mission鈥恖ength timescales, particularly for sensor offsets, while sensor gains and angles are remarkably stable. Offset variations are correlated with sensor temperature—for the Cluster 1 instrument in particular—and to a lesser extent with electronics temperature; coefficients are of the order 0.1 and 0.01 nT/ºC respectively. After correction for temperature effects, there is no clearly measurable offset drift over the mission lifetime. Statistics for all four spacecraft are presented. These data could be used to inform the design andimplementation of future missions employing fluxgate magnetometers. The spacecraft are found to bemagnetically “clean,” which allows in鈥恌light calibration techniques to be applied with confidence and precision,leading to consistently high鈥恞uality magnetic鈥恌ield data sets available through the Cluster Science Archive.
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Journal articleCanu P, Bouzid V, Piberne R, et al., 2026, , Journal of Geophysical Research: Space Physics, Vol: 131, ISSN: 2169-9380
The Spatio-Temporal Analysis of Field Fluctuations(STAFF) instruments onboard the Cluster satellites were designed to measure magnetic fluctuations in the 0.2–12 Hz and 0.2–180 Hz frequency ranges from the Search-Coil Magnetometer (SCM), as well as electromagnetic spectra from the Spectrum Analyzer (SA) in the 8–4000 Hz range. They provided a considerable amount of data throughout the 24-year mission. The production and calibration of these datasets were detailed in Robert et al. (2014), which demonstrated its excellent quality and good agreement with the FluxGate Magnetometer (FGM) measurements over their commonfrequency range. The Cluster's 24 years of operation, which far exceed the nominal two-year mission, represent the longest flight of search coil magnetometers and offer a unique opportunity to evaluate their performance over such a long period, as well as to compare the results of four initially identical instruments. The present work, based on data now archived at the Cluster Scientific Archive (CSA), examines the evolution of these products after the first 11 years in space, and until the end of the Cluster operations in September 2024. The quality of the measurements, calibration, sensitivities, and their agreement between spacecraft proved to be excellent and remained stable throughout the mission. Comparison of spectra derived from the calibrated waveforms of STAFF (CWF) and FGM shows a very good agreement until the end of operations, a further proof of the high quality of their respective calibrations.
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Journal articleSvenningsson I, Yordanova E, Khotyaintsev YV, et al., 2026, , Phys Rev E, Vol: 113
Despite heat flux's role in regulating energy conversion in collisionless plasmas, its properties and evolution in the magnetosheath downstream of the Earth's bow shock are scarcely explored. We use Magnetospheric Multiscale in situ measurements to quantify and characterize the electron heat flux in the magnetosheath. We find that the heat flux is shaped by the magnetosheath magnetic field as it drapes around the magnetosphere. While it is affected by solar wind upstream conditions and increases with magnetic field strength, it is not substantially changed by local magnetosheath processes. Also, the heat flux is limited by whistler instability thresholds.
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Journal articleKelly H, Archer M, Eastwood J, et al., 2026, , Geophysical Research Letters, Vol: 53, ISSN: 0094-8276
The Kelvin-Helmholtz instability (KHI) mediates the viscous-like solar-terrestrial interaction by generating magnetopause surface waves that quickly become non-linear. Basic theory predicts the locally most-unstable linear wave dominates. However, Kelvin-Helmholtz is a broad, convective instability that also amplifies waves originating upstream. We address this conundrum by applying dynamic mode decomposition to a Gorgon global magnetohydrodynamic simulation of the KHI. While distinct modes quickly grow at points along the magnetopause, signaling local generation, their energy continues to slowly grow downtail. Thus, a superposition is present along the magnetopause, where the dominant mode is not always the locally fastest-growing. Each mode's wavelength elongates downtail, correlating with the boundary layer flow speed due to the accelerating advective flow around the magnetosphere Doppler shifting the fixed-frequency waves. This may explain why longer wavelengths are observed in the tail than theory predicts and motivates further exploration of tangential inhomogeneities in basic Kelvin-Helmholtz theory.
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Journal articleWilson LB, Bale SD, Stevens ML, et al., 2026, , Astrophysical Journal, Vol: 1002, ISSN: 0004-637X
Between 2005 January 1 and 2017 November 25, the Wind spacecraft measured 3,996,051 electron velocity distribution functions (VDFs) in the near-Earth solar wind. The instrument was calibrated, and velocity moments were calculated up to the third moment (i.e., electron heat flux). The magnetic field and ion velocity moments have been interpolated to the midpoint time of the VDFs, where we have 3,947,607 finite electron velocity moments (most prior studies used <300,000 moments). The median values for the velocity moments are as follows: n<inf>e,int</inf> ∼ 5.43 cm<sup>−3</sup>, 鈭<inf>oe</inf>鈭 ∼ 421 km s<sup>−1</sup>, T<inf>e,tot</inf> ∼ 12.7 eV, and 鈭<inf>e,鈭</inf>鈭 ∼4.92 μW m<sup>−2</sup>. The median values for the electron-to-proton temperature ratio is (Formula presented) Te,tot/Tp,tot ∼2.55, the electron temperature anisotropy A<inf>e</inf> = (Formula presented) Te,⊥/Te,鈭 ∼ 0.89, total electron beta β<inf>e,tot</inf> ∼ 1.27, electron–electron collision frequency ν<inf>ee</inf>鈥嬧嬧嬧 ∼ 0.18 day<sup>−1</sup>, and electron–electron Knudsen number K<inf>n,ee</inf> ∼ 2.57. The results are mostly consistent with previous studies except that K<inf>n,ee</inf> is significantly larger than some other works, which implies that the near-Earth solar wind is less collisional than may have been inferred.
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Journal articleLewis H, Eastwood J, Phan T, et al., 2026, , The Astrophysical Journal (ApJ), Vol: 1002, Pages: 1-12, ISSN: 0004-637X
In situ observations by Parker Solar Probe (PSP) suggest that the heliospheric current sheet (HCS) undergoes near-continuous magnetic reconnection close to the Sun, in stark contrast to scarce observations of this phenomenon in the HCS at 1 AU. Situated at the boundary between sectors of opposite interplanetary magnetic field (IMF) polarity, reconnection in the HCS has important consequences for magnetic topology and plasma dynamics in the slow solar wind. We report observations of a reconnection outflow in theHCS near the Alfv´en transition region in PSP’s 17th solar encounter, featuring plasma jetting, proton temperature enhancement, and electron heat flux dropout. Embedded within the exhaust is a non-force-free flux rope plasmoid exhibiting counterstreaming strahl electrons, indicating connection at both ends to the Sun in an otherwise disconnected region of magnetic field. The flux rope features diminished isotropic protontemperature and lower bulk speed compared to the remainder of the HCS exhaust. Its oblique orientation and different plasma properties imply the flux rope originates from a different reconnection site to the HCS exhaust, suggesting PSP has intercepteda flux-rope-like streamer blob produced at the helmet streamer. Remote observations show several comparable blobs travelling in a distant coronal ray, demonstrating the possibility that the in situ flux rope is a streamer blob. The combination of in situ andremote observations demonstrate the role of magnetic reconnection in HCS dynamics, contributing to a growing understanding of this fundamental mechanism and its impact on the young solar wind.
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Journal articleHorbury T, OBrien HL, Greenaway C, et al., 2026,
The IMAP magnetometer
, Space Science Reviews, Vol: 222, ISSN: 0038-6308The magnetometer (MAG) is one of the ten scientific instruments on the Interstellar Mapping and Acceleration Probe (IMAP), which will take in situ and remote measurements from a Sun- Earth L1 halo orbit. MAG contributes to IMAP science goals of investigating the acceleration and propagation of energetic particles, as well as providing real-time space weather monitoringdata. The magnetometer is a conventional dual sensor fluxgate instrument with a noise floor under 10 pT at 1 Hz, taking science measurements continuously at 2 vectors/s as well as a burst mode of 64 vectors/s for at least 8 hours per day. It also provides a real-time space weathermonitoring product at 4 second cadence. We describe the requirements, design and performance of the instrument, including a novel lossless compression algorithm. Data products, processing and calibration plans are presented.
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