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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 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
- Citations: 3
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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 -
Journal articleBreul P, Ceppi P, Nowack P, 2025,
The importance of stratocumulus clouds for projected warming patterns and circulation changes
, Atmospheric Chemistry and Physics (ACP), Vol: 25, Pages: 11991-12005, ISSN: 1680-7316Stratocumulus clouds are thought to exert a strong positive radiative feedback on climate change, but recent analyses suggest that this feedback is widely under-represented in global climate models. To assess the broader implications of this model error for the simulated climate change responses, we investigate the impact of Pacific stratocumulus cloud feedback on projected warming patterns, equilibrium climate sensitivity and tropical atmospheric circulation under increased CO2 concentrations. Using the Community Earth System Model, with modifications to enhance low-cloud-cover sensitivity to sea surface temperature (SST) anomalies in Pacific stratocumulus regions, we find increased tropical SST variability and persistence, a higher equilibrium climate sensitivity, an enhanced east–west warming contrast across the tropical Pacific, and a stronger slowdown of the Walker circulation under 4×CO2 conditions. Our findings are supported by inter-model relationships across CMIP6 4×CO2 simulations. These results underscore the importance of accurately representing cloud feedback in climate models to predict future climate change impacts not only globally but also on a regional scale, such as warming patterns or circulation change.
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Journal articleTsui EYL, Toumi R, 2025,
Re‐intensification of seafalling tropical cyclones
, Atmospheric Science Letters, Vol: 26, ISSN: 1530-261XThe study of tropical cyclones re-entering the ocean or making ‘seafall’ has been limited. Here, idealised simulations are used to study the re-intensification of seafalling tropical cyclones. They follow a two-stage fast-slow process driven predominately by a change in surface friction initially and then by heating. The previous land decay causes seafalling tropical cyclones to be larger and intensify more slowly with milder inner-core contraction than in ocean-only cases. Nonetheless, they reach the same intensity but with almost twice the integrated kinetic energy, so that the second landfall made by seafalling tropical cyclones can cause more damage due to their larger footprint of destructive wind.
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Journal articleCargill PJ, Hood AW, Johnson D, 2025,
Heating and cooling at a coronal magnetic null
, Monthly Notices of the Royal Astronomical Society, Vol: 542, Pages: 3385-3394, ISSN: 0035-8711Conductive cooling of the solar corona at a magnetic null is examined. An initial equilibrium is set up, balancing thermal conduction and a constant spatially uniform coronal heating. The heating is then turned off and the subsequent conductive cooling calculated. An equation for the cooling is obtained using the method of separation of variables and it is shown that the equations for the equilibrium between conduction and heating, and the time-dependent cooling are mathematically identical with a simple change of variables. Thus, the properties of the cooling phase are automatically determined by the equilibrium state. For a two-dimensional null, the characteristic cooling time-scale increases over that in a straight field by a factor of between 2 and 5, with a scaling determined by the ratio of the average and base areas of a flux element. There is no explicit dependence on the very large areas that can arise near the null.
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Journal articleWaters CL, Eastwood JP, Fargette N, et al., 2025,
Bridging in situ satellite measurements and simulations of magnetic reconnection using recurrent neural networks
, Journal of Geophysical Research: Space Physics, Vol: 130, ISSN: 2169-9380Magnetic reconnection is inherently structured, with distinct spatial regions such as inflows, outflows, and separatrices playing key roles in energy conversion and particle transport. While in situ spacecraft measurements provide detailed local information, determining where a spacecraft lies within the global reconnection geometry remains a major challenge. Proxy-based methods are often ambiguous, while full reconstructions require strong assumptions and are difficult to apply systematically across events. Here, we present a method that bridges these approaches by using machine learning to infer global structural context from local measurements. We first apply k-means clustering to a 2.5-D particle-in-cell simulation to identify six characteristic symmetric reconnection regions. A recurrent neural network (RNN) is then trained on spacecraft-like trajectories through the simulation to classify time series data into these regions. When applied to Magnetospheric Multiscale (MMS) observations of magnetotail reconnection, this method successfully identifies regional transitions, including inflow, outflow, and separatrix crossings, in agreement with previous reconstructions where available. The approach provides a practical, scalable, and automated framework for determining spatial context in reconnection events without requiring full geometric reconstruction, enabling large-scale and efficient statistical studies of reconnection dynamics across multiple events.
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Journal articleDesai RT, Perrin J, Meredith NP, et al., 2025,
Multi-MeV Electron Occurrence and Lifetimes in the Outer Radiation Belt and Slot Region During the Maximum of Solar Cycle 22
, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 23 -
Journal articleDing M, Lim SZJ, Yu X, et al., 2025,
A neural network approach for line detection in complex atomic emission spectra measured by high-resolution Fourier transform spectroscopy
, MACHINE LEARNING-SCIENCE AND TECHNOLOGY, Vol: 6 -
Journal articleTrotta D, Horbury TS, Giacalone J, 2025,
Variability in energetic particle observations at strong interplanetary shocks: Multi-spacecraft observations
, ASTRONOMY & ASTROPHYSICS, Vol: 702, ISSN: 0004-6361 -
Journal articleArcher M, Evans V, Eastwood J, et al., 2025,
First detection of field-aligned currents using engineering magnetometers from the OneWeb mega-constellation
, Space Weather, ISSN: 1539-4956 -
Journal articleAuestad H, Shibu A, Ceppi P, et al., 2025,
The Latent Heating Feedback on the Mid-Latitude Circulation
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleRivera YJ, Klein KG, Wang JH, et al., 2025,
Observational Constraints on the Radial Evolution of O<SUP>6+</SUP> Temperature and Differential Flow in the Inner Heliosphere
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 990, ISSN: 2041-8205 -
Journal articleHuang Z, Velli M, Chandran BDG, et al., 2025,
Two Types of 1/<i>f</i> Range in Solar Wind Turbulence
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 990, ISSN: 2041-8205 -
Journal articleKrasnoselskikh V, Jebaraj IC, Cooper TRF, et al., 2025,
Plasma Instability in Front of Ejected Energetic Electrons and Type III Solar Radio Bursts
, ASTROPHYSICAL JOURNAL, Vol: 990, ISSN: 0004-637X -
Journal articleRovithakis A, Burke E, Burton C, et al., 2025,
Estimating future wildfire burnt area over Greece using the JULES-INFERNO model
, Natural Hazards and Earth System Sciences, Vol: 25, Pages: 3185-3200, ISSN: 1561-8633Our previous studies have shown that fire weather conditions in the Mediterranean and specifically over Greece are expected to become more severe with climate change, impling potential increases in burnt area. Here, we employ the Joint UK Land Environment Simulator (JULES) coupled with the INFERNO fire model driven by future climate projections from the UKESM1 model to investigate the repercussions of climate change and future vegetation changes on burnt area over Greece. We validate modelled burnt area against the satellite-derived GFED5 dataset, and find the model's performance to be good, especially for the more fire-prone parts of the country in the south Greece. For future simulations, we use future climate data following three Shared Socioeconomic Pathways (SSPs), consisting of an optimistic climate change scenario where fossil fuel emissions peak and decline beyond 2020 (SSP126), a middle-of-the-road scenario (SSP370), and a pessimistic scenario where emissions continue to rise throughout the century (SSP8.5). Our results show increased burnt area in the future compared to the present-day period in response to overall hotter and drier climatological conditions. We use an additional JULES-INFERNO simulation in which dynamic vegetation was activated, and find that it features smaller future burned area increases compared to our simulation with static present-day vegetation. For this dynamically changing vegetation simulation the greatest burnt area increases are found for southern Greece, due to higher future availability of flammable and heat-resistant needleleaf trees and the smallest decreases in agricultural areas of northern Greece due to a reduction in the aforementioned tree category.
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Journal articleSakellaris IA, Bartzis JG, Grillakis E, et al., 2025,
Simulation of Air Pollution Produced by Forest Fires Using the WRF-SFIRE-CHEM Model in Greece: Study Cases
, FIRE TECHNOLOGY, ISSN: 0015-2684 -
Journal articlePanditharatne S, Cox C, Song R, et al., 2025,
Exploiting airborne far-infrared measurements to optimise an ice cloud retrieval
, Atmospheric Chemistry and Physics, Vol: 25, Pages: 9981-9998, ISSN: 1680-7316Studies have indicated that far-infrared radiances hold significant information about the microphysics of ice clouds, particularly the ice crystal habit. In support of the European Space Agency's Far-Infrared Outgoing Radiation Understanding and Monitoring mission, we perform the first retrieval on an observation of coincident upwelling far- and mid-infrared radiances taken from an aircraft above a cirrus cloud layer. Four retrievals are performed: including and neglecting the far-infrared portion of the spectrum and assuming two different habit mixes. Results are compared to in situ measurements of the cloud optical thickness, cloud top height, cloud effective radius, and habit distributions. We find that despite the known limitations of ice cloud optical property models, all the retrievals show agreement within the in situ measurements of the cloud optical thickness, cloud top height, and cloud effective radius. However, the inclusion of the far-infrared enables a distinction between two different habits that is not possible using only mid-infrared channels. Furthermore, in this case study, the uncertainty in the retrieval of cloud top height and cloud optical thickness halves with the inclusion of the far-infrared. As with other studies, we also see an additional degree of freedom for the temperature and water vapour retrievals. Our study highlights the need for the improvement of current ice cloud optical models, with the radiance residuals from the converged retrievals still exceeding the instrument uncertainty within the far-infrared. However, it provides observational support for the theoretical improvement that far-infrared observations could bring to retrievals of ice cloud properties.
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Journal articleElsden T, Southwood DJ, Allanson O, et al., 2025,
Theory and modeling of large scale plasmapause surface waves
, Journal of Geophysical Research: Space Physics, Vol: 130, ISSN: 2169-9380The plasmapause in Earth's magnetosphere represents the boundary between the plasma which co-rotates with the Earth (plasmasphere), and the more tenuous plasmatrough outside. The density change across the plasmapause can be large, changing by approximately 1–2 orders of magnitude depending on the prevailing conditions. This would suggest it to be a location where magnetohydrodynamic (MHD) surface waves can form, and indeed, this has been proposed in previous works to explain ultra-low frequency (ULF) wave observations around the plasmapause location. The main question is how such a large scale surface wave on the plasmapause would be excited. In this paper, we propose a model whereby surface waves at the plasmapause are driven by energy input from the magnetopause through solar wind driving. We derive an analytical form for the amplitude of these surface waves with this new driven boundary condition at the magnetopause. The excitation of these waves is then tested in several MHD simulations, where the model geometry, wavenumbers and temporal dependence of the magnetopause driver are varied. We establish that surface waves on the plasmapause can be excited by driving from the magnetopause, and that this still occurs with impulsive and continuous broadband driving. The azimuthal scale of the wave is a critical factor for this excitation, with longer azimuthal scales more favorable for driving larger amplitude surface waves. This mechanism provides new insight for how large scale and large amplitude ULF waves can access the inner magnetosphere, with potential implications for their interaction with radiation belt particles.
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Journal articleFrankignoul C, Hall R, Kwon Y-O, et al., 2025,
On the Atmospheric Response to Oyashio Extension Front Disturbance and Mesoscale SST Variations
, JOURNAL OF CLIMATE, Vol: 38, Pages: 5055-5066, ISSN: 0894-8755 -
Journal articleKoike M, Takigawa M, Morimoto S, et al., 2025,
Studies of atmospheric climate forcers in the Arctic during the ArCS II project
, POLAR SCIENCE, Vol: 45, ISSN: 1873-9652- Cite
- Citations: 2
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Journal articlePathak N, Ergun RE, Vo T, et al., 2025,
Observations of Large-Amplitude Parallel Electric Fields in the Turbulent Magnetotail
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 130, ISSN: 2169-9380 -
Journal articleKawaguchi K, Ceppi P, 2025,
Responses to Lower-Tropospheric Stability Dominate Intermodel Differences in the Historical Pattern Effect
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleToumi R, Sparks N, 2025,
The Hurricane Damage Index (HurDI)
, Journal of Catastrophe Risk and Resilience, Vol: 03, ISSN: 3049-7604Statistical hurricane risk assessments make long-term multi-decadal stationary climate assumptions, but there is large hurricane variability in the risk. It would be useful to also better estimate the “current” risk. The hurricane damage index (HurDI), is proposed as a measure of the underlying non-stationary risk. The HurDI is defined as the normalised annual average damage calculated with a stochastic wind only model, a single damage function, and uniform exposure across the continental U.S. The stochastic model is climate conditioned by weighting the historical basin hurricane counts, potential intensity, and tracks. The weights are chosen to give the best persistence forecast for each parameter for the next five years. There has been a substantial increase of the hurricane risk as measured by the HurDI. In 2024, the index was at a record high of 188, with a reference value of 100 in 1989. The HurDI is a dynamic view of risk based on the hurricane variability only and can be compared to U.S. property catastrophe reinsurance rates. There are periods of varying difference between the rates and the HurDI reflecting the volatile market cycles.
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Journal articleBowen TA, Mallet A, Dunn CI, et al., 2025,
Formation of magnetic switchbacks via expanding Alfvén waves
, ASTRONOMY & ASTROPHYSICS, Vol: 700, ISSN: 0004-6361 -
Journal articleNorgren C, Chen L-J, Graham DB, et al., 2025,
Electron and ion dynamics in reconnection diffusion regions
, Space Science Reviews, Vol: 221, ISSN: 0038-6308Magnetic reconnection is a fundamental plasma process responsible for the sometimes explosive release of magnetic energy in space and laboratory plasmas. Inside the diffusion regions of magnetic reconnection, the plasma becomes demagnetized and decouples from the magnetic field, enabling the change in magnetic topology necessary to power the energy release over larger scales. Since it was launched in 2015, the Magnetospheric MultiScale (MMS) mission has significantly advanced the understanding of the particle dynamics key to magnetic reconnection by providing high-resolution, in-situ measurements able to resolve ion and electron kinetic scales, i.e. a fraction of a gyroradius, that have confirmed theoretical predictions, revealed new phenomena, and refined existing models. These breakthroughs are critical for understanding not only space plasmas but also laboratory and astrophysical plasmas where magnetic reconnection occurs. In this work, we review the ion and electron dynamics occurring within the diffusion regions, in the inflow, along the separatrices, and downstream of the diffusion regions, in different reconnection configurations: symmetric, asymmetric, antiparallel, and guide field reconnection.
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Journal articleLewis ZM, Stephenson P, Beth A, et al., 2025,
Cometary ion dynamics at 67P: a collisional test-particle approach with Rosetta data comparison
, Monthly Notices of the Royal Astronomical Society, Vol: 541, Pages: 3590-3605, ISSN: 0035-8711The Rosetta spacecraft escorted comet 67P/Churyumov–Gerasimenko for two years, gathering a rich and variable data set.Amongst the data from the Rosetta Plasma Consortium (RPC) suite of instruments are measurements of the total electron densityfrom the Mutual Impedance Probe (MIP) and Langmuir Probe (LAP). At low outgassing, the plasma density measurements canbe explained by a simple balance between the production through ionization and loss through transport. Ions are assumed totravel radially at the outflow speed of the neutral gas. Near perihelion, the assumptions of this field-free chemistry-free modelare no longer valid, and plasma density is overestimated. This can be explained by enhanced ion transport by an ambipolarelectric field inside the diamagnetic cavity, where the interplanetary magnetic field does not reach. In this study, we explore thetransition between these two regimes, at intermediate outgassing (5.4 × 1026 s−1), when the interaction between the cometaryand solar wind plasma influences the transport of the ions. We use a 3D collisional test-particle model, adapted from Stephensonet al. to model the cometary ions with input electric and magnetic fields from a hybrid simulation for 2.5–3 au. The total plasmadensity from this model is then compared to data from MIP/LAP and to the field-free chemistry-free model. In doing so, wehighlight the limitations of the hybrid approach and demonstrate the importance of modelling collisional cooling of the electronsto understand the ion dynamics close to the nucleus.
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Journal articlePage B, Lecacheux A, Pulupa M, et al., 2025,
Calibration of Electrically Short Antennas Using the <i>l</i>=2 Spherical Harmonic Expansion Coefficients of the Radio Brightness Distribution on the Sky Between 0.5 and 6.8 MHz
, RADIO SCIENCE, Vol: 60, ISSN: 0048-6604 -
Journal articleVan de Koot EK, Byrne MP, Woollings T, 2025,
Tropical Cloud Feedbacks Estimated from Observed Multidecadal Trends
, Journal of Climate, Vol: 38, Pages: 3185-3199, ISSN: 0894-8755<jats:title>Abstract</jats:title><jats:p>Tropical cloud feedbacks are an important source of uncertainty in estimates of climate sensitivity. The extent to which changes in atmospheric circulation contribute to these feedbacks remains an open question. Here, all-sky radiative flux observations and an atmospheric reanalysis are used to estimate tropical cloud feedbacks from multidecadal trends (1985–2020) in cloud radiative effect and surface temperature. We decompose the observed feedbacks into dynamic and nondynamic components to quantify the impact of circulation trends. Narrowing and strengthening of tropical ascent lead to substantial dynamic feedbacks on regional scales that are similar in magnitude to the nondynamic feedbacks. However, as previously shown for high- and low-resolution climate models, large dynamic feedbacks in different circulation regimes are connected by the atmospheric mass budget and approximately cancel when averaged across the tropics due to the quasi-linear relationship between cloud radiative effect and vertical velocity. This results in small dynamic contributions to the tropical-mean net, longwave, and shortwave feedbacks. We suggest that this result will hold in future and thus that isolating the nondynamic components associated with individual cloud types can provide important insights into the processes controlling the tropical-mean cloud feedback and its uncertainty. Additionally, we show that feedbacks estimated from multidecadal trends differ from those estimated from interannual variability. We demonstrate that, for dynamic feedbacks, this is because changes are controlled by different mechanisms and this leads to a differing spatial distribution of temperature sensitivity. Finally, we provide new estimates of the uncertain combined tropical anvil area and albedo feedback using both multidecadal trends and interannual variability.</jats:p>
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