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Journal articleSnodgrass C, Mazzotta Epifani E, Tubiana C, et al., 2026,
Considerations on the process of target selection for the Comet Interceptor mission
, Icarus, Vol: 447, ISSN: 0019-1035Comet Interceptor is an ESA science mission with payload contributions from ESA Member States and with an international participation by JAXA. It is the first mission that is being designed, built, and potentially launched before its target is known. This approach will enable the spacecraft to perform the first mission to a Long Period Comet from the Oort Cloud, as these comets have fleeting visits to the inner Solar System lasting only months to years from first discovery, too short for the usual process of mission development to be followed. In this paper we describe a number of factors that need to be considered in selecting a target for the mission, including scientific, orbital, spacecraft and instrument constraints, and discussion of different prioritisation strategies. We find that, in the case where we have a choice of targets, our decisions will mostly be driven by orbital information, which we will have relatively early on, with information on the activity level of the comet an important but secondary consideration. As cometary activity levels are notoriously hard to predict based on early observations alone, this prioritisation / decision approach based more on orbits gives us confidence that a good comet that is compatible with the spacecraft constraints will be selectable with sufficient warning time to allow the mission to intercept it.
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Journal articleSharan S, Pais A, Amit H, et al., 2025,
Fluid flow at the top of Jupiter's dynamo region
, Journal of Geophysical Research: Planets, ISSN: 2169-9097The magnetic main field (MF) and secular variation (SV) models for Jupiter can be used to gain insights about the internal dynamo and the flow that drives the field. We use two such models computed from Juno observations up to spherical harmonic degrees 16 and 8 for the MF and SV, respectively. We solve the radial magnetic induction equation in the frozen-flux approximation, at the dynamo region outer boundary assuming zero radial velocity for four large-scale physical flow assumptions- unconstrained, toroidal, tangentially geostrophic and columnar. We find flows with root mean square velocity varying between 100 and 400 km/yr (0.3-1.3 cm/s) when the dynamo region spherical boundary is taken at 0.83 Jupiter radius. Equatorially symmetric, toroidal and non-zonal velocity components are larger than the anti-symmetric, poloidal and zonal components, respectively, for almost all cases. Toroidal and tangentially geostrophic flows display similar velocity values and patterns, despite relying on different physical assumptions. The four inverted solutions indicate that the Jovian interior has dominant eastward flows nearthe Great Blue Spot, in agreement with previous studies. In addition, our more complex flow models shed light on some new features such as a large non-zonal component,meridional flows in the southern hemisphere and field-aligned flows in the north. Finally, our unconstrained flow solution suggests upwelling near the south pole, consistent withn thermal wind theory.
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Journal articleRiddell-Young B, Michel SE, Lan X, et al., 2025,
Microbial driver of 2006–2023 CH <sub>4</sub> growth indicated by trends in atmospheric δD–CH <sub>4</sub> and δ <sup>13</sup> C–CH <sub>4</sub>
, Proceedings of the National Academy of Sciences, Vol: 122, ISSN: 0027-8424<jats:p> Methane (CH <jats:sub>4</jats:sub> ) is the second most important greenhouse gas and has been rising following a brief period of stabilization from 1999 to 2006. Determining the cause of this rise is critical for reducing emissions and predicting future climate sensitivity. The carbon and hydrogen stable isotopic composition of atmospheric CH <jats:sub>4</jats:sub> is controlled by variability in isotopically distinguishable emission categories and fractionating sink processes. While most studies using atmospheric δ <jats:sup>13</jats:sup> C–CH <jats:sub>4</jats:sub> data suggest a dominantly microbial source for recent CH <jats:sub>4</jats:sub> growth, this understanding is not uniform, and uncertainties remain [S. Schwietzke <jats:italic toggle="yes">et al.</jats:italic> , <jats:italic toggle="yes">Nature</jats:italic> <jats:bold>538</jats:bold> , 88–91 (2016), S. Basu <jats:italic toggle="yes">et al.</jats:italic> , <jats:italic toggle="yes"> <jats:italic toggle="yes">Atmos. Chem. Phys.</jats:italic> </jats:italic> <jats:bold>22</jats:bold> , 15351–15377 (2022), J. Thanwerdas, M. Saunois, A. Berchet, I. Pison, P. Bousquet, <jats:italic toggle="yes">Atmos. Chem. Phys.</jats:italic> <jats:bold>24</jats:bold> , 2129&n
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Journal articleHall RJ, Jones JM, Fogt RL, et al., 2025,
Variability and Trends of the Amundsen Sea Low since the Early Twentieth Century from Seasonal-Station-Based Reconstructions
, Journal of Climate, Vol: 38, Pages: 7509-7527, ISSN: 0894-8755<jats:title>Abstract</jats:title> <jats:p>The Amundsen Sea is dominated by a quasi-stationary low-pressure region, the Amundsen Sea low (ASL). ASL variability impacts regional weather and the basal melting of ice shelves, an important contributor to sea level rise. To understand trends and variability of the ASL, it is important to have data for a long time period. However, the shortness of the satellite record starting in 1979 and the sparseness of Antarctic observational data prior to this make understanding variability on decadal scales challenging. Century-long reanalyses are available but have well-known pressure biases, meaning that trends cannot be reliably quantified. Other reconstructions are available at the annual resolution but mask important seasonal differences. Here, we reconstruct the ASL at seasonal resolution from 1905, using Southern Hemisphere weather station sea level pressure data, which takes advantage of well-known teleconnections between the tropics and Antarctica, although the strength of these is seasonally dependent and varies decadally. We compare our reconstructions with two centennial reanalyses and ERA5. Our reconstruction captures early twentieth-century variability associated with ice shelf melting and retreat and places recent ASL trends in a longer-term context. We find that the recent deepening of the ASL across all seasons is unprecedented since 1905, and there is increased uncertainty in the ASL index during the mid-twentieth century. We also assess the stationarity of the association between station data and the ASL by using data from a Pacific pacemaker climate model experiment. The stationarity assumption for our ASL reconstruction is valid, except for the austral autumn due to insufficient data availability.</jats:p> <jats:sec> <jats:title>Significance Statement</jats:title> <jats:p>Our study provides a no
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Journal articleWong HL, Palacios R, Gryspeerdt E, 2025,
rojak: A Python library and tool for aviation turbulence diagnostics
, Journal of Open Source Software, Vol: 10, ISSN: 2475-9066Aviation turbulence is atmospheric turbulence occurring at length scales large enough (ap proximately 100m to 1km) to affect an aircraft (Sharman, 2016). According to the National Transport Safety Board (NTSB), turbulence experienced whilst onboard an aircraft was theleading cause of accidents from 2009 to 2018 (NTSB, 2021). Clear air turbulence (CAT) is a form of aviation turbulence which cannot be detected by the onboard weather radar. Thus, pilots are unable to preemptively avoid such regions. In order to mitigate this safety risk, CAT diagnostics are used to forecast turbulent regions such that pilots are able to tactically avoidthem.rojak is a parallelised Python library and command-line tool for using meteorological data to forecast CAT and evaluating the effectiveness of CAT diagnostics against turbulence observations. Currently, it supports,1. Computing turbulence diagnostics on meteorological data from the European Centrefor Medium-Range Weather Forecasts’s (ECMWF) ERA5 reanalysis on pressure levels(Hersbach, 2023). Moreover, it is easily extendable through a software update to supportother types of meteorological data.2. Retrieving and processing turbulence observations from Aircraft Meteorological DataRelay (AMDAR) data archived at the National Oceanic and Atmospheric Administration(NOAA)(NCEP Meteorological Assimilation Data Ingest System (MADIS), 2024) andAMDAR data collected via the Met Office MetDB system (Met Office, 2008)3. Computing 27 different turbulence diagnostics, such as the three-dimensional fronto genesis equation (Bluestein, 1993), turbulence index 1 and 2 (Ellrod & Knapp, 1992),negative vorticity advection (Sharman et al., 2006), and Brown’s Richardson tendencyequation (Brown, 1973).4. Converting turbulence diagnostic values into the eddy dissipation rate (EDR) — the International Civil Aviation Organization’s (ICAO) official metric for reporting turbulence (Meteorological Service for International Air Navigati
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Journal articleWarwick L, Oetjen H, Murray J, et al., 2025,
In Situ Measurements of Ice and Snow Emissivity in the Far-Infrared
, Earth and Space Science, Vol: 12This paper describes the first field deployment of the Far INfrarEd Spectrometer for Surface Emissivity far-infrared Fourier transform spectrometer to an Arctic environment and shows retrievals of the emissivity of ice and snow in the wavenumber range 400–1,200 cm<sup>−1</sup> at viewing angles of 35° and 50°. The retrieved ice emissivity shows a variation of 0.05 between the peak value at around 950 cm<sup>−1</sup> and the minimum value at around 750 cm<sup>−1</sup>. The emissivity is also between 0.01 and 0.02 lower for the higher viewing angle. The emissivity of snow is higher and shows less variation with both viewing angle and wavenumber but it is 0.01 less than one below 900 cm<sup>−1</sup>. This has implications for remote sensing and climate modeling in this wavenumber range as it implies that both the spectral and angular variation of emissivity must be taken into account. The retrieved ice emissivity agrees well with the emissivity modeled using Fresnel equations. The retrieved snow emissivity agrees well with modeled snow emissivity but further independent measurements of the snow physical properties are needed to test the performance of the model in the far infrared.
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Journal articleBreul P, Ceppi P, Simpson IR, et al., 2025,
Seasonal and regional jet stream changes and drivers
, Nature Reviews Earth and Environment, Vol: 6, Pages: 824-842The eddy-driven jet streams, which are regions of strong westerly wind in the mid-latitudes of both hemispheres, exert a leading influence on regional climate. In this Review, we outline the seasonally and regionally varying drivers, characteristics and changes in the jet streams. State-of-the-art models commonly predict a future polewards shift of the zonal-mean and annual-mean jet streams, typically ranging between 0° and 2° latitude by the end of the century under a high-emissions scenario, but with large model-to-model uncertainty. Furthermore, regional and seasonal projections can deviate substantially from the annual-mean and zonal-mean picture, and the drivers of these projected changes are not fully understood. Jet trends have emerged in the reanalysis record since 1979, of which a polewards shift of the summertime austral jet of ~0.3° per decade is the trend most clearly attributable to anthropogenic forcing. Although other trends have been observed, potentially large internal variability and incomplete understanding of the drivers of these trends precludes clear anthropogenic attribution at this point. Research is unevenly distributed across regions and seasons, with winter receiving the most attention, particularly in the North Atlantic. To support physical understanding and impact assessments, future research should provide a more complete picture of the seasonally and regionally varying jet stream drivers, and their changes, especially in spring and autumn.
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Journal articleLee CO, Christian ER, Sandoval L, et al., 2025,
Space Weather Science to Enhance Forecasting with the NASA IMAP Active Link for Real-Time (I-ALiRT) System
, Space Science Reviews, Vol: 221, ISSN: 0038-6308The Interstellar Mapping and Acceleration Probe (IMAP) is a NASA heliophysics science mission that provides new coordinated and comprehensive observations of the inner and outer heliosphere. The IMAP observatory orbits at the Sun-Earth L1 Lagrange point, which is an ideal location for observing the space weather conditions upstream of Earth. Thus, in addition to providing new and groundbreaking heliophysics science observations, five in-situ instruments on IMAP make measurements that are critical for advancing space weather research and operational forecasting. These measurements are continuously telemetered in near real-time as part of the IMAP Active Link for Real-Time (I-ALiRT) space weather data system. I-ALiRT is based on the Real-Time Solar Wind (RTSW) data system from the NASA Advanced Composition Explorer (ACE) mission and provides similar space weather data products at enhanced cadences as well as additional new data products. This paper describes the I-ALiRT instruments and measurements, real-time data flow architecture, and publicly available space weather data products.
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Journal articleKang H, Choi Y, 2025,
Estimating Tropical Upper‐Level Cloud Feedback Based on Radiative‐Convective Equilibrium Framework
, Geophysical Research Letters, Vol: 52, ISSN: 0094-8276<jats:title>Abstract</jats:title> <jats:p> Tropical upper‐level cloud (TUC) feedback remains highly uncertain because TUC fraction and its radiative effect respond in complex ways to sea surface temperature (SST) warming. Using a radiative–convective equilibrium (RCE) model, we isolate the radiative impact of TUC changes by adjusting the relative occurrence of clouds and water vapor across the tropics. The resulting TUC feedback parameter, estimated from RCE experiments with observationally constrained versus CMIP6‐derived TUC fractions, is more negative for observational inputs (−1.66 to −1.24 W m <jats:sup>−2</jats:sup> K <jats:sup>−1</jats:sup> ) and spans a much broader range for CMIP6 inputs (−1.34 to +1.78 W m <jats:sup>−2</jats:sup> K <jats:sup>−1</jats:sup> ). The stronger negative feedback with observational inputs likely reflects a larger reduction in TUCs with SST warming. In contrast, CMIP6‐based parameters indicate weaker radiative effects of SST‐driven TUC reductions, suggesting that climate models may underestimate this negative feedback. </jats:p>
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Journal articleLivadiotis G, Cuesta ME, Khoo LY, et al., 2025,
Entropy transfer from solar radio bursts to energetic particles.
, Sci Adv, Vol: 11Space plasma thermodynamics is thought to be affected by wave activity. Here, we show that solar radio bursts (SRBs) can transfer entropy to solar energetic protons (SEPs), affecting their thermodynamics. In particular, our analysis (i) detects the statistically significant SEP density fluctuations, associated with SRB activity that triggers a systematic increase in the thermodynamic kappa; (ii) estimates the polytropic index of SEPs, which is anticorrelated with kappa, serving as an independent measure to validate the increase in kappa; (iii) derives the entropy transfer by using its theoretical relationship with kappa; and (iv) compares SRB wave intensity with the entropy transferring to SEPs to demonstrate their wave-particle coupling. We lastly expose the thermodynamic association between type III SRB wave intensity and SEP entropy transfer as well as their respective coupling, thus developing a paradigm for further systematic investigations among other types of wave activity and particle populations.
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Journal articleWilliams RG, Goodwin P, Ceppi P, et al., 2025,
A normalised framework for the Zero Emissions Commitment
, Biogeosciences, Vol: 22, Pages: 7167-7186, ISSN: 1726-4170The Zero Emissions Commitment (ZEC) measures the transient climate response after carbon emissions cease, defined by whether there is a continued rise or decrease in global surface temperature. This delayed climate response affects the maximum cumulative carbon emission to avoid exceeding a warming target. In a set of 9 Earth system models following an idealised atmospheric CO<inf>2</inf> scenario with a cumulative emission of 1000 Pg C, the ZEC after 50 years ranges from −0.3 to 0.28 °C with a model mean of −0.11 °C and standard deviation of 0.19 °C. In order to understand these different climate responses, a normalised framework is introduced that quantifies the relative importance of carbon, radiative and thermal drivers of the ZEC. Inter-model differences in the ZEC are primarily due to differences in the radiative response, planetary heat uptake and the land carbon sink, with more minor contributions from differences in the ocean carbon sink and climate feedback. The ZEC response is controlled by opposing-signed contributions: (i) cooling from a decrease in radiative forcing from a carbon contribution due to increasing land and ocean carbon uptake, versus (ii) surface warming from a thermal contribution involving a decline in the fraction of radiative forcing used for planetary heat uptake plus possible amplification by climate feedback. The carbon contribution to the ZEC depends on the increase in the ocean carbon sink and whether the land carbon sink either increases or saturates in time. The thermal contribution to the ZEC depends upon how radiative forcing is partitioned between planetary heat uptake and radiative response with the radiative response either declining in time or remaining constant. These inferences as to the controls of the ZEC broadly carry over for diagnostics for a large ensemble, observationally-constrained, efficient Earth system model using two different emission scenarios to reach net zero. The larg
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Journal articleDriver OGA, Stettler MEJ, Gryspeerdt E, 2025,
The ice supersaturation biases limiting contrail modelling are structured around extratropical depressions
, Atmospheric Chemistry and Physics (ACP), Vol: 25, Pages: 16411-16433, ISSN: 1680-7316Contrails are ice clouds formed along aircraft flight tracks, responsible for much of aviation's climate warming impact. Ice-supersaturated regions (ISSRs) provide conditions where contrail ice crystals can persist, but meteorological models often mispredict their occurrence, limiting contrail modelling. This deficiency is often treated by applying local humidity corrections. However, model performance is also affected by synoptic conditions (such as extratropical depressions).Here, composites of ERA5 reanalysis data around North Atlantic extratropical depressions enable a link between their structure and ISSR modelling. ISSRs are structured by these systems: at flight levels, ISSRs occur less frequently in the dry intrusion – descending upper-tropospheric air – than above warm conveyors – where air is lifted. Both ERA5 reanalysis and in situ aircraft observations show this contrast, demonstrating that the model reproduces the fundamental relationship. Individual-ISSR modelling performance (quantified using interpretable metrics) is also structured. Of the rare ISSRs diagnosed in the location associated with the dry intrusion, fewer are confirmed by in situ observations (20 %–25 % precision drop compared to the warm conveyor) and fewer of those observed were diagnosed (13 %–19 % recall drop). Scaling humidity beyond the occurrence rate bias dramatically increases the recall at low precision cost, demonstrating the potential value of scaling approaches designed with different intentions. However, the failure of scaling to improve precision, or the performance in the dry intrusion, implies that there is a need to account for the synoptic weather situation and structure in order to improve ISSR forecasts in support of mitigating aviation's climate impact.
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Journal articlePugsley G, Gryspeerdt E, Nair V, 2025,
Cloud fraction response to aerosol driven by nighttime processes
, Proceedings of the National Academy of Sciences of USA, ISSN: 0027-8424 -
Journal articleYufei Y, Timothy H, Domenico T, et al., 2025,
Ion-scale solitary structures in the solar wind observed by Solar Orbiter and Parker Solar Probe
, Astrophysical Journal Letters, Vol: 994, ISSN: 2041-8205We investigate a class of ion-scale magnetic solitary structures in the solar wind, characterized by distinct magnetic field enhancements and bipolar rotations over spatial scales of several proton inertial lengths. These structures are revisited using high-resolution data from the Solar Orbiter and Parker Solar Probe missions. Using a machine learning-based method, we identified nearly a thousand such structures, providing new insights into their evolution and physical properties. Statistical analysis shows that these structures are more abundant closer to the Sun, with occurrence rates peaking around 30 - 40 Rsun and decreasing farther out. High-cadence measurements reveal that these structures are predominantly found in low-beta (beta <1) environments, with consistent fluctuations in density, velocity, and magnetic field. Magnetic field enhancements are often accompanied by plasma density drops, which, under near pressure balance, limit field increases. This leads to small fractional field enhancements near the Sun (approximately 0.01 at 20 Rsun), making detection challenging. Magnetic field variance analysis indicates that these structures are primarily oblique to the local magnetic field. Alfvénic velocity-magnetic field correlations suggest that most of these structures, unlike most near-Sun solar wind fluctuations, exhibit sunward-directed Alfvenic polarization in the plasma frame. We compare these findings with previous studies, discussing possible generation mechanisms and their implications for the turbulent cascade in the near-Sun Alfvénic solar wind. While these structures might be Alfvénic solitons, vortices, or flux ropes, we refrain from a definitive classification pending further evidence. Further high-resolution observations and simulations are needed to fully understand their origins and impacts.
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Journal articleDasgupta B, Menoud M, van der Veen C, et al., 2025,
Harmonisation of methane isotope ratio measurements from different laboratories using atmospheric samples
, Atmospheric Measurement Techniques, Vol: 18, Pages: 6591-6607, ISSN: 1867-1381Establishing interlaboratory compatibility among measurements of stable isotope ratios of atmospheric methane (δ<sup>13</sup>C-CH<inf>4</inf> and δD-CH<inf>4</inf>) is challenging. Significant offsets are common because laboratories have different ties to the VPDB or SMOW-SLAP scales. Umezawa et al. (2018) surveyed numerous comparison efforts for CH<inf>4</inf> isotope measurements conducted from 2003 to 2017 and found scale offsets of up to 0.5 ‰ for δ<sup>13</sup>C-CH<inf>4</inf> and 13 ‰ for δD-CH<inf>4</inf> between laboratories. This exceeds the World Meteorological Organisation Global Atmospheric Watch (WMO-GAW) network compatibility targets of 0.02 ‰ and 1 ‰ considerably. We employ a method to establish scale offsets between laboratories using their reported CH<inf>4</inf> isotope measurements on atmospheric samples. Our study includes data from eight laboratories with experience in high-precision isotope ratio mass spectrometry (IRMS) measurements for atmospheric CH<inf>4</inf>. The analysis relies exclusively on routine atmospheric measurements conducted by these laboratories at high-latitude stations in the Northern and Southern Hemispheres, where we assume each measurement represents sufficiently well-mixed air at the latitude for direct comparison. We use two methodologies for interlaboratory comparisons: (I) assessing differences between time-adjacent observation data and (II) smoothing the observed data using polynomial and harmonic functions before comparison. The results of both methods are consistent, and with a few exceptions, the overall average offsets between laboratories align well with those reported by Umezawa et al. (2018). This indicates that interlaboratory offsets remain robust over multi-year periods. The evaluation of routine measurements allows us to calculate the interlaborator
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Journal articleLi J-H, Khotyaintsev YV, Graham DB, et al., 2025,
Solar Orbiter Observations of a Self-Consistent Ion-Scale Magnetic Hole at 0.9AU
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleMuro GD, Cohen CMS, Xu Z, et al., 2025,
Energy-Dependent SEP Fe/O Abundances During the May 2024 Superstorm
, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 23 -
ReportClarke B, Barnes C, Keeping T, et al., 2025,
Climate change enhanced intensity of Hurricane Melissa, testing limits of adaptation in Jamaica and eastern Cuba
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Journal articleVon Salzen K, Akingunola A, Cole JNS, et al., 2025,
Reduced aerosol pollution diminished cloud reflectivity over the North Atlantic and Northeast Pacific
, Nature Communications, Vol: 16, ISSN: 2041-1723Over the past several decades, the proportion of solar radiation reflected back into space has declined, accelerating the accumulation of heat within the Earth system. Here we show that the marine cloud reflectivity decreased on average by 2.8 ± 1.2% per decade in the combined North Atlantic and Northeast Pacific regions between 2003 and 2022. The majority of the Earth System Models we analyzed simulated a significantly weaker cloud reflectivity decrease and warming of the sea surface in these regions than observed. In contrast, our simulations using an improved aerosol-climate model reproduce the spatial extent and magnitude of the observed cloud reflectivity decrease. We show that reductions in sulfur dioxide and other aerosol precursors accounted for 69% (range 55−85%) of the cloud reflectivity decrease through aerosol-cloud interactions, consistent with the observed aerosol and cloud trends. This raises the prospect of a continuing cloud reflectivity decrease and an associated warming impact in these regions, given that the emission reductions are projected to persist over the next few decades. Further research is needed to assess whether near-term climate scenarios should be revised to account for the weak cloud reflectivity reductions in the Earth System Models.
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Journal articleGrimmich N, Settino A, Nykyri HK, et al., 2025,
Comparison of Kelvin–Helmholtz waves observed simultaneously at the dawn and dusk flanks of the Earth’s magnetopause
, Planetary and Space Science, Vol: 267, ISSN: 0032-0633Across the Earth’s magnetopause, unless the magnetic fields stabilise the boundary, the velocity shear between the magnetospheric plasma and the shocked plasma of the solar wind can lead to the Kelvin–Helmholtz instability. This instability can develop into large-scale surface waves and vortices at the magnetopause, causing the different plasma regions to mix, which plays an important role in the transfer of energy across the magnetopause. We know from spacecraft observations and simulations that the way Kelvin–Helmholtz waves grow and evolve can be different at dawn and dusk. However, very few studies have directly observed this phenomenon on both flanks of the magnetopause simultaneously, nor have they provided a consistent explanation for the question of symmetrical or asymmetrical dawn–dusk growth of the waves. By combining measurements from the THEMIS and Cluster missions, we can report here on an event where such a simultaneous observation of the Kelvin–Helmholtz waves is possible.For this event, we investigate and compare the typical wave parameters and the plasma mixing on the two flanks. Our results suggest an asymmetric evolution of the Kelvin–Helmholtz waves at dawn and dusk. Comparing these results with previous studies of simultaneously observed events and linking them to solar wind conditions further shows that this asymmetric growth seems to occur during the Parker spiral IMF, but probably only if the magnetic fields are strong enough to effectively stabilise the boundary at the dusk flank due to field line draping.
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Journal articleMandikas VG, Voulgarakis A, 2025,
High-Resolution Numerical Scheme for Simulating Wildland Fire Spread
, Mathematics, Vol: 13Predicting wildland fire spread requires numerical schemes that can resolve sharp gradients at the fireline while remaining stable and efficient on practical grids. We develop a compact high-order finite-difference scheme for Hamilton–Jacobi level-set formulations of wildfire propagation, based on the anisotropic spread law of Mallet and co-authors. The spatial discretization employs a compact finite-difference derivative scheme to achieve spectral-like resolution with narrow stencils, improving accuracy and boundary robustness compared with wide-stencil ENO/WENO reconstructions. To control high-frequency artifacts intrinsic to non-dissipative compact schemes, an implicit high-order low-pass filter is incorporated and activated after each Runge–Kutta stage. Convergence is verified on the eikonal expanding-circle benchmark, where the method attains the expected high-order spatial accuracy as the grid is refined. The proposed scheme is then applied to wind-driven wildfire simulations governed by Mallet’s non-convex Hamiltonian, including a single ignition under moderate and strong wind. A complex topology test case is also considered, involving two ignitions that merge into a single front with the evolution of an internal unburnt island. The results demonstrate that the proposed method accurately reproduces fireline evolution even on coarse grids, achieving accuracy comparable to fifth-order WENO while maintaining superior fidelity in complex fireline topologies, where it better resolves multi-front interactions and topological changes in the fireline. This makes the method an efficient, accurate alternative for level-set wildfire modeling and readily integrable into existing frameworks.
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Journal articleCuesta ME, Fraschetti F, Livadiotis G, et al., 2025,
Distinct Solar Energetic Particle Shock Intensity-Diffusion Coefficient Relationships in the Inner Heliosphere
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 993, ISSN: 2041-8205 -
Journal articleErgun RE, Qi Y, Vo T, et al., 2025,
Electron Acceleration in Magnetic Reconnection-driven Turbulence in the Earth's Magnetotail
, ASTROPHYSICAL JOURNAL, Vol: 993, ISSN: 0004-637X -
Journal articleHalekas JS, Whittlesey P, Larson DE, et al., 2025,
Electrons in the Collisionally Young Solar Wind: Parker Solar Probe Observations
, ASTROPHYSICAL JOURNAL, Vol: 993, ISSN: 0004-637X -
Journal articleBeth A, Galand M, Jia X, et al., 2025,
Ion-neutral chemistry at icy moons: the case of Ganymede
, Monthly Notices of the Royal Astronomical Society, Vol: 544, Pages: 95-112, ISSN: 0035-8711Icy moons orbiting giant planets are often described as airless bodies though they host an exosphere where collisions between neutral species are scarce. In the case of Ganymede, the neutral composition is dominated by H2O, H2, and O2. Past observations by Galileo showed that Ganymede hosts an ionosphere and those by Juno revealed the presence of H+3 , an ion species onlystemming from ion-neutral collisions. H+3 detection suggests that ions and neutrals might still collide and be the source of new ion species on icy moons. We examine Ganymede’s ability to host a more diverse ionosphere in terms of ion composition than previously thought and predict its variety. We upgraded our test-particle code of Ganymede’s ionosphere, formerly collisionless,to include ion-neutral collisions in a probabilistic manner. The updated code is applied to three Galileo flybys of Ganymede that were investigated in the absence of chemistry. Both sets of simulations have been compared and the effect of ion-neutral chemistry has been assessed. We show that in the case of an exosphere predominantly composed of H2O, H2, and O2, theionosphere is made not only of their associated cations but also of H+3 , H3O+, and O2H+. Simulations reveal that, depending on the location, the contribution of H+3 and H3O+ to the ion composition may be significant. Strong dayside/nightside and Jovian/anti-Jovian asymmetries in the ion composition are identified. Our findings are key to interpreting Juno and future JUICEion mass spectrometer data sets.
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Journal articleSparks N, Toumi R, 2025,
The impact of global warming on U.S. hurricane landfall: a storyline approach
, Environmental Research Letters, Vol: 20, ISSN: 1748-9326The projection of hurricane activity under climate change is challenging. The Imperial College Storm Model (IRIS) was used to analyse the impact of global warming on North Atlantic hurricane landfall through a storyline approach. The storyline assumes increases of potential intensity (PI) as the cause of change with no changes to tracks or basin frequency. This allows study of both recenttrends and projections for the first time in a consistent way. The observed hurricane intensification is simulated but underestimated. For a +2◦C global warming scenario hurricanes of intensity Category 4 and above become 62% more likely in the basin and nearly twice (92%) more likely at landfall. The future number of hurricanes, their decay and tracks are uncertain and their impact is examined by sensitivity studies. Reduction of the basin count offsets warming driven landfall frequency increases only for weaker hurricanes. The increased frequency and fraction of the most damaging landfalling hurricanes is controlled by changes in PI.
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Journal articleMcComas DJ, Christian ER, Schwadron NA, et al., 2025,
Interstellar Mapping And Acceleration Probe: The NASA IMAP Mission
, SPACE SCIENCE REVIEWS, Vol: 221, ISSN: 0038-6308- Cite
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Journal articleGuillaume-Castel R, Ceppi P, Dorrington J, et al., 2025,
ENSO Diversity Explains Interannual Variability of the Pattern Effect
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleErvin T, Mallet A, Eriksson S, et al., 2025,
The Impact of Alfvénic Shear Flow on Magnetic Reconnection and Turbulence
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 992, ISSN: 2041-8205
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