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Abstract

Since the Voyager mission flybys in 1979, we have known the moon Io to be both volcanically active and the main source of plasma in the vast magnetosphere of Jupiter. Material lost from Io forms neutral clouds, the Io plasma torus and ultimately the extended plasma sheet. This material is supplied from Io’s upper atmosphere and atmospheric loss is likely driven by plasma-interaction effects with possible contributions from thermal escape and photochemistry-driven escape. Direct volcanic escape is negligible. The supply of material to maintain the plasma torus has been estimated from various methods at roughly one ton per second. Most of the time the magnetospheric plasma environment of Io is stable on timescales from days to months. Similarly, Io’s atmosphere was found to have a stable average density on the dayside, although it exhibits lateral (longitudinal and latitudinal) and temporal (both diurnal and seasonal) variations. There is a potential positive feedback in the Io torus supply: collisions of torus plasma with atmospheric neutrals are probably a significant loss process, which increases with torus density. The stability of the torus environment may be maintained by limiting mechanisms of either torus supply from Io or the loss from the torus by centrifugal interchange in the middle magnetosphere. Various observations suggest that occasionally (roughly 1 to 2 detections per decade) the plasma torus undergoes major transient changes over a period of several weeks, apparently overcoming possible stabilizing mechanisms. Such events (as well as more frequent minor changes) are commonly explained by some kind of change in volcanic activity that triggers a chain of reactions which modify the plasma torus state via a net change in supply of new mass. However, it remains unknown what kind of volcanic event (if any) can trigger events in torus and magnetosphere, whether Io’s atmosphere undergoes a general change before or during such events, and what processes could enable such a change in the otherwise stable torus. Alternative explanations, which are not invoking volcanic activity, have not been put forward. We review the current knowledge on Io’s volcanic activity, atmosphere, and the magnetospheric neutral and plasma environment and their roles in mass transfer from Io to the plasma torus and magnetosphere. We provide an overview of the recorded events of transient changes in the torus, address several contradictions and inconsistencies, and point out gaps in our current understanding. Lastly, we provide a list of relevant terms and their definitions.

Information on geomagnetic field intensity in the past is essential for understanding the behavior and mechanism of the geodynamo. A fundamental unresolved problem of relative paleointensity (RPI) estimations ...

When people think about fiber optic cables, it's usually about how they're used for telecommunications and accessing the internet. But fiber optic cables—strands of glass or plastic that allow for the transmission of light—can be used for another purpose: imaging the ground beneath our feet.

Biochar, a charcoal-like material derived from plant biomass, has long been hailed as a promising tool for carbon dioxide removal. However, a new study by Stanford researchers highlights a critical issue: current methods for assessing biochar's carbon storage potential may significantly undervalue its true environmental benefits.

Computer models reveal how human-driven climate change will dramatically overhaul critical nutrient cycles in the ocean. In the Proceedings of the National Academy of Sciences, University of California, Irvine researchers report evidence that marine nutrient cycles—essential for sustaining ocean ecosystems—are changing in unexpected ways as the planet continues to warm.

С 17 по 21 февраля 2025 года в здании Президиума Российской академии наук (РАН, г. Москва, Ленинский проспект, 32А) состоится научная сессия-конференция Секции ядерной физики Отделения физических наук (ОФН) РАН "Физика фундаментальных взаимодействий", посвящённая памяти выдающегося всемирно известного российского физика-теоретика, академика РАН Валерия Анатольевича Рубакова.
На конференции планируется заслушать следующие пленарные доклады:

17 февраля 2025 г.

1. Сергеев А.М. (Национальный центр физики и математики (НЦФМ), г. Саров, Нижегородская обл.).Экстремальные световые поля.
2. Бутенко А.В. (Объединённый институт ядерных исследований (ОИЯИ), г. Дубна, Московская обл.). Установки проекта NICA.
3. Рябов В.Г. (ФГБУ "Петербургский институт ядерной физики им. Б.П. Константинова Национального исследовательского центра (НИЦ) "Курчатовский институт", г. Санкт-Петербург; Объединённый институт ядерных исследований, г. Дубна, Московская обл.). Эксперименты на ускорительном комплексе NICA.
4. Брагута В.В. (Объединённый институт ядерных исследований, г. Дубна, Московская обл.). Барионная материя при экстремальных условиях.

18 февраля 2025 года

5. Левичев Е.Б. (Институт ядерной физики им. Г.И. Будкера СО РАН, г. Новосибирск). Обзор перспективных ускорительных проектов для физики частиц.
6. Ольшевский А.Г. (Объединённый институт ядерных исследований, г. Дубна, Московская обл.). Изучение осцилляций нейтрино в ускорительных и реакторных экспериментах: результаты и перспективы/
7. Барабаш А.С. (Институт теоретической и экспериментальной физики имени А.И. Алиханова Национального исследовательского центра "Курчатовский институт", г. Москва). Масса нейтрино: прямые измерения и двойной бета-распад.
8. Алексеев И.Г. (Национальный исследовательский центр "Курчатовский институт", г. Москва). Поиск лёгких стерильных нейтрино.
9. Сюняев Р.А. (Институт космических исследований РАН, г. Москва; Max Planck Institute for Astrophysics, Garching, Germany). Результаты и перспективы миссии Спектр—Рентген—Гамма.

19 февраля 2025 года

10. Мурин Ю.А. (Объединённый институт ядерных исследований, г. Дубна, Московская обл.). Детекторные системы в релятивистской ядерной физике сегодня и завтра.
11. Образцов В.Ф. (Институт физики высоких энергий, НИЦ "Курчатовский институт", г. Протвино, Московская обл.). Последние результаты по распадам каонов.
12. Дружинин В.П. (Институт ядерной физики им. Г.И. Будкера СО РАН, г. Новосибирск). Изучение e+e− аннигиляции в адроны на коллайдерах ИЯФ.
13. Xiaorong Zhou (University of Science and Technology of China). The Project of Super Tau-Charm Factory in China.

20 февраля 2025 года

14. Сильченко О.К. (Московский государственный университет им. М.В. Ломоносова, Государственный астрономический институт им. П.К. Штернберга, г. Москва). Молодые галактики на красном смещении больше 9: новые данные и парадигма.
15. Быков А.М. (Физико-технический институт им. А.Ф. Иоффе РАН, г. Санкт-Петербург). Фотоны, нейтрино и космические лучи высоких энергий в нашей Галактике.
16. Кузнецов М.Ю. (Институт ядерных исследований РАН, г. Москва). Космические лучи с энергиями выше 1019 эВ: новые результаты и новые загадки.
17. Джилкибаев Ж.-А. М. (Институт ядерных исследований РАН, г. Москва). Астрофизические результаты Байкальского нейтринного телескопа.

21 февраля 2025 года

18. Кузьмичев Л.А. (Московский государственный университет им. М.В. Ломоносова, Научно-исследовательский институт ядерной физики им. Д.В. Скобельцына, г. Москва). Крупномасштабные детекторы для исследований космических излучений.
19. Никитенко А.Н. (Национальный исследовательский центр "Курчатовский институт", г. Москва; Imperial College, London, UK). Поиски Новой Физики за пределами Стандартной Модели на Большом Адронном Коллайдере.
20. Пешеходов Д.В. (Объединённый институт ядерных исследований, г. Дубна, Московская обл.). Последние результаты эксперимента NA64 в CERN.
21. Дудко Л.В. (Московский государственный университет им. М.В. Ломоносова, Научно-исследовательский институт ядерной физики им. Д.В. Скобельцына, г. Москва). Физика топ-кварка.

20 февраля 2025 года в рамках сессии-конференции "Физика фундаментальных взаимодействий" состоится мемориальная сессия, посвящённая научному наследию академика Валерия Анатольевича Рубакова.
Избранные доклады конференции, содержащие новые результаты, будут опубликованы в журнале "Ядерная физика".

The Pliocene epoch, which lasted from 5.3 million to 2.6 million years ago, was a consequential time in Earth's history. The Isthmus of Panama formed, connecting North and South America, and the accumulation of ice at the poles reshaped the world's biogeography.

Observing Greenland from a helicopter, the main problem is one of comprehending scale. I have thought we were skimming low over the waves of a fjord, before noticing the tiny shadow of a seabird far below and realizing what I suspected were floating shards of ice were in fact icebergs the size of office blocks. I have thought we were hovering high in the sky over a featureless icy plane below, before bumping down gently onto ice only a few meters below us.

A University of Hawaii at Mānoa study on the freezing of water droplets suspended in air sheds light on a key process in Earth's water cycle: the transformation of supercooled water into ice.

An international group of scientists, led by King's College London, has revealed how continued global warming will lead to more parts of the planet becoming too hot for the human body over the coming decades.

A new study debunks claims that a magnitude 4.5 earthquake in Iran was a covert nuclear weapons test, as widely alleged on social media and some mainstream news outlets in October 2024, a period of heightened geopolitical tensions in the Middle East.

Abstract

Trends in the deep-ocean M \(_2\) barotropic tide, deduced from nearly three decades of satellite altimetry and recently presented by Opel et al. (Commun Earth Environ 5:261, https://doi.org/10.1038/s43247-024-01432-5, 2024), are here updated with a slightly longer time series and with a focus on potential systematic errors. Tidal changes are very small, of order 0.2 mm/year or less, with a tendency for decreasing amplitudes, which is evidently a response to the ocean’s increasing stratification and an increasing energy loss to baroclinic motion. A variety of systematic errors in the satellite altimeter system potentially corrupt these small trend estimates. The Dynamic Atmosphere Correction (DAC), derived from an ocean model and used for de-aliasing, introduces a spurious trend (exceeding 0.1 mm/year in places) caused by changes in ECMWF atmospheric tides. Both operational and reanalysis atmospheric tides have spurious trends over the altimeter era. Tidally coherent errors in satellite orbits, including from use of inconsistent tidal geocenter models, are more difficult to bound, although differences between two sets of satellite ephemerides are found to reach 0.1 mm/year for M \(_2\) . Orbit errors are more deleterious for some other constituents, including the annual cycle. Tidal leakage in the “mesoscale correction,” needed here to suppress non-tidal ocean variability, is a known potential problem, and if the leakage changes over time, it impacts ocean-tide trend estimation. Tests show the error is likely small in the open ocean ( \(<0.04\)  mm/year) but large in some marginal seas ( \(>0.2\)  mm/year). Potential contamination from other altimeter corrections (e.g., ionospheric path delay) is likely negligible for M \(_2\) but can be difficult to bound.

SummaryWe conducted comparative measurements of thermal properties of samples from nine cores of the ICDP COSC-1 borehole and four widely used rock references, using a steady-state and a transient divided-bar device, a transient plane source device, a modified Ångström device, as well as two optical thermal conductivity scanners. In addition, a caloric method provided benchmark values for specific heat capacity. A complementary thin-section analysis of the COSC-1 samples allowed us to calculate specific heat capacity according to Kopp’s law and thermal conductivity according to commonly used mixing models. Our results demonstrate agreement between the various test methods within ±10% for about one half of the investigated samples. Furthermore, almost all results for specific heat capacity agree with the predictions of Kopp’s law, though the significance of this correspondence is limited owing to large uncertainties in the experimental and theoretical values. The results for thermal conductivity fall within the most extreme theoretical bounds that account for anisotropy but for an amphibolite. Thermal anisotropy seems to contribute significantly to the deviations between results of the different transient methods that, however, cannot be reconciled by the available theoretical relations for apparent thermal conductivity of transversely isotropic materials. The combination of characteristic investigation volume of the individual methods and sample heterogeneity has to be considered responsible for variability of results, too, an issue whose clarification is calling for dedicated numerical modelling in the future, with the prospect to characterise thermal heterogeneity from observed differences.

SummaryElastodynamic Green’s functions are an essential ingredient in seismology as they form the connection between direct observations of seismic waves and the earthquake source. They are also fundamental to various seismological techniques including physics-based ground motion prediction and kinematic or dynamic source inversions. In regions with established 3D models of the Earth’s elastic structure, such as southern California, 3D Green’s functions can be computed using numerical simulations of seismic wave propagation. However, such simulations are computationally expensive which poses challenges for real-time ground motion prediction and uncertainty quantification in source inversions. In this study, we address these challenges by using a reduced-order model (ROM) approach that enables the rapid evaluation of approximate Green’s functions. The ROM technique developed approximates three-component time-dependent surface velocity wavefields obtained from numerical simulations of seismic wave propagation. We apply our ROM approach to a 50 km × 40 km area in greater Los Angeles accounting for topography, site effects, 3D subsurface velocity structure, and viscoelastic attenuation. The ROM constructed for this region enables rapid computation (≈0.0001 CPU hours) of complete, high-resolution (500 m spacing), 0.5 Hz surface velocity wavefields that are accurate for a shortest wavelength of 1.0 km for a single elementary moment tensor source. Using leave-one-out cross validation, we measure the accuracy of our Green’s functions for the CVM-S velocity model in both the time domain and frequency domain. Averaged across all sources, receivers, and time steps, the error in the rapid seismograms is less than 0.01 cm/s. We demonstrate that the ROM can accurately and rapidly reproduce simulated seismograms for generalized moment tensor sources in our region, as well as kinematic sources by using a finite fault model of the 1987 MW 5.9 Whittier Narrows earthquake as an example. We envision that rapid, accurate Green’s functions from reduced-order modeling for complex 3D seismic wave propagation simulations will be useful for constructing real-time ground motion synthetics and source inversions with high spatial resolution.

SummaryWe aim to improve our comprehension of the seismic process and to identify possible long-term predictability tools of strong earthquakes through the simulation performed by a new-generation simulator code based on a well-elaborated model of the earthquake sources. We applied our previously tested physics-based earthquake simulator to the Nankai megathrust fault system, characterised by a 13 centuries historical record of strong earthquakes. Our results show these significant seismicity patterns characterizing the seismic cycles: the average stress increases almost linearly, while its standard deviation decreases more and more rapidly as the next major earthquake approaches; the co-seismic stress drop and the simultaneous increase of the standard deviation mark the beginning of the new seismic cycle; and the b-value tends to increase some decades before major earthquakes and exhibits correlation with the occurrence rate. Our results encourage further investigations about the application of simulators in support of other methodologies of earthquake forecasting.

SummaryA grain-based stress corrosion model is built from 3DEC-GBM (i.e., a three-dimensional discrete element grain-based model). The model employs the effective stress law and stress corrosion theory to study the time-dependent and time-independent deformation at the mesoscale of the sandstone with varying confining and pore pressures. The simulations adequately explain complex macroscopic time-independent behavior in terms of the mesoscale interaction of grains, and tension cracks were the dominant crack propagation pattern in the simulation for different confining and pore pressures. The traditional creep behavior observed in laboratory brittle creep experiments could also be accurately reproduced by the proposed model. The simulations show that the percentage of tension cracks in rock fractures decreases with increasing confining pressure and pore pressures. Increasing the applied differential stress and reducing the effective pressure can shorten time-to-failure and increase the creep strain rate, respectively. We conclude that the proposed model is an appropriate tool to analyze the deformation behavior of sandstone under coupled hydro-mechanical loading in both the short and long term.

SummaryThis paper introduces a comprehensive framework for modelling both instantaneous and time-dependent elastic softening in anisotropic materials at high pressure and temperature. This framework employs Landau Theory, minimizing the Helmholtz energy by varying isochemical parameters (q) that capture structural changes, atomic ordering, and/or electronic spin states. This allows for internally consistent predictions of volume, unit cell parameters, the elastic tensor, and other thermodynamic properties, while allowing large symmetry-breaking strains. The formulation is validated using the stishovite-to-post-stishovite transition. It is demonstrated that, near this transition, both stishovite and post-stishovite exhibit auxetic behaviour in several directions, with post-stishovite also displaying negative linear compressibility along the long axis of its unit cell (either the a or b axis). The new formulation is implemented in the open-source BurnMan software package.

SummarySeismic and electrical surveys are the most employed geophysical exploration applications for understanding the subsurface earth. Differential effective medium (DEM) models are the models to interpret the seismic and electrical survey data with the greatest success. However, cementation exponent and pore aspect ratio as the indispensable geometric parameters in the electrical and elastic DEM models are independent, making the models not suitable for the joint elastic-electrical modelling, a key requirement for the joint interpretation of seismic and electrical exploration data to better understand the increasingly complex hydrocarbon reservoirs. We show how cementation exponent and pore aspect ratio are correlated in three Berea sandstone samples with changing porosity resulting from varying pore pressure. We find that cementation exponent inverted from the electrical DEM model shows a strong positive linear correlation with pore aspect ratio obtained from the elastic DEM model as an implicit function of porosity induced by increasing pore pressure. We also find that the established linear correlation can enable the DEM models to calculate one physical property (e.g., elastic or electrical) from the geometric parameter describing the other property (e.g., electrical or elastic). The results reveal how the elastic and electrical geometric parameters are linked, and provide a consistent microstructure that enables the existing elastic and electrical DEM models to be suitable for the joint elastic-electrical modelling of rocks undergoing varying pore pressure.

Abstract

Global navigation satellite system (GNSS) Doppler measurements are immune to cycle slips, providing a robust way to detect ionospheric irregularities. This study presents a novel approach to detect equatorial plasma bubble (EPB) using a support vector machine (SVM) algorithm based on the GNSS Doppler measurements. The input of the detector is the Doppler index (DI), which is extracted from the dual-frequency differential Doppler observations. Data from HKWS station located in Hong Kong during 2022 are employed to train the SVM model and validate its performance. The results show the trained SVM model achieves 96.7% validation accuracy of EPB detection. To assess the general capability of the model, EPB events throughout the entire year of 2023 are investigated at both the HKWS station and the HYDE station. The results show the performance of EPB detection by the SVM model using DI is comparable to that of by visually inspecting the total electron content time series based on GNSS carrier-phase measurements. In addition, the characteristics of EPB occurrence are also consistent to previous studies, suggesting the detection results are reliable.

Abstract

Chondritic meteorites (chondrites) contain evidence for the interaction of liquid water with the interiors of small bodies early in Solar System history. Here we review the processes, products and timings of the low-temperature aqueous alteration reactions in CR, CM, CI and ungrouped carbonaceous chondrites, the asteroids Ryugu and Bennu, and hydrated dark clasts in different types of meteorites. We first consider the nature of chondritic lithologies and the insights that they provide into alteration conditions, subdivided by the mineralogy and petrology of hydrated chondrites, the mineralogy of hydrated dark clasts, the effects of alteration on presolar grains, and the evolution of organic matter. We then describe the properties of the aqueous fluids and how they reacted with accreted material as revealed by physicochemical modelling and hydrothermal experiments, the analysis of fluid inclusions in aqueously formed minerals, and isotope tracers. Lastly, we outline the chronology of aqueous alteration reactions as determined using the 53Mn-53Cr and 129I-129Xe systems.