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We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays.

In this study, we analyzed a rare hard, bright X‐ray burst associated with intense natural lightning. Through spectral analysis and source model fitting, we demonstrate that the energy spectrum of the X‐ray source region exhibits significant uncertainty due to the strong dependence on radiation beam geometry, which may appear as a TGF‐like hard spectrum. The X‐ray burst is estimated to produce approximately 1013 to 1014 source photons (>30 keV), which is 1–2 orders of magnitude higher than a typical X‐ray burst and comparable to the brightness of downward TGFs. The hard, bright X‐ray burst challenges the traditional classification boundary between soft/weak X‐rays and hard/strong TGFs, suggesting that both may exist in a continuous spectrum. The generation mechanism for such hard, bright X‐ray bursts may involve Relativistic Runaway Electron Avalanche processes, though likely in an incomplete stage.

Nonlinear energy sink (NES) refers to a typical passive vibration device connected to linear or weakly nonlinear structures for vibration absorption and mitigation. This study investigates the dynamics of 1-dof and 2-dof NES with nonlinear damping and combined stiffness connected to a linear oscillator. For the system of 1-dof NES, a truncation damping and failure frequency are revealed through bifurcation analysis using the complex variable averaging method. The frequency detuning interval for the existence of the strongly modulated response (SMR) is also reported. For the system of 2-dof NES, it is reported in a similar bifurcation analysis that the mass distribution between NES affects the maximum value of saddle-node bifurcation. To obtain the periodic solution of the 2-dof NES system with the consideration of frequency detuning, the incremental harmonic balance method (IHB) and Floquet theory are employed. The corresponding response regime is obtained by Poincare mapping, it shows that the responses of the linear oscillator and 2-dof NES are not always consistent, and 2-dof NES can generate extra SMR than 1-dof NES. Finally, the vibration suppression effect of the proposed NES with nonlinear damping, and combined stiffness is analyzed and verified by the energy spectrum, and it also shows that the 2-dof NES system demonstrates better performance.

The Relativistic Runaway Electron Avalanche (RREA) is the primary mechanism for enhancing atmospheric electron and gamma‐ray fluxes when the electric field exceeds a density‐dependent threshold. Another, non‐threshold process—Modification of the Electron Energy Spectrum (MOS)—occurs when subcritical fields energize ambient electrons, shifting their spectrum to higher energies and increasing bremsstrahlung probability. MOS becomes dominant at high energies, where the RREA flux rapidly decreases, explaining the persistent detections of gamma rays above 50–60 MeV. We simulate gamma‐ray yield over a wide range of Atmospheric Electric Field (AEF) to delineate MOS and RREA regimes and quantify spectral evolution with field strength. Experimental data from two Thunderstorm Ground Enhancements (TGEs) observed on 2 October 2024, are analyzed. By matching the exponential growth of measured count rates to modeled RREA yield, we derive the temporal evolution of the AEF during both TGEs, revealing the rate and magnitude of field strengthening that drive particle bursts and bridge the MOS–RREA transition in natural thunderstorms.

ERA5 represents the state of the art for atmospheric reanalyses and is widely used in meteorological and climatological research. In this work, this dataset is evaluated using the wind kinetic energy spectrum. Seasonal climatologies are generated for 30° latitudinal bands in the Northern Hemisphere (periodic domain) and over the North Atlantic area (limited-area domain). The spectra are also assessed to determine the effective resolution of the reanalysis. The results present notable differences between the latitudinal domains, indicating that ERA5 is properly capturing the synoptic conditions. The seasonal variability is adequate too, being winter the most energetic, and summer the least energetic season. The limited area domain results introduce a larger energy density and range. Despite the good results for the synoptic scales, the reanalysis’ spectra are not able to properly reproduce the dissipation rates at mesoscale. This is a source of uncertainties which needs to be taken into account when using the dataset. Finally, a cyclone tropical transition is presented as a case study. The spectrum generated shows a clear difference in energy density at every wavelength, as expected for a highly-energetic status of the atmosphere.

We expand on a recent determination of the first global energy spectrum of the ocean's surface geostrophic circulation (Storer et al., 2022, https://doi.org/10.1038/s41467-022-33031-3) using a coarse‐graining (CG) method. We compare spectra from CG to those from spherical harmonics by treating land in a manner consistent with the boundary conditions. While the two methods yield qualitatively consistent domain‐averaged results, spherical harmonics spectra are too noisy at gyre‐scales (>1,000 km). More importantly, spherical harmonics are inherently global and cannot provide local information connecting scales with currents geographically. CG shows that the extra‐tropics mesoscales (100–500 km) have a root‐mean‐square (rms) velocity of ∼15 cm/s, which increases to ∼30–40 cm/s locally in the Gulf Stream and Kuroshio and to ∼16–28 cm/s in the ACC. There is notable hemispheric asymmetry in mesoscale energy‐per‐area, which is higher in the north due to continental boundaries. We estimate that ≈25%–50% of total geostrophic energy is at scales smaller than 100 km, and is un(der)‐resolved by pre‐SWOT satellite products. Spectra of the time‐mean circulation show that most of its energy (up to 70%) resides in stationary eddies with characteristic scales smaller than (<500 km). This highlights the preponderance of “standing” small‐scale structures in the global ocean due to the temporally coherent forcing by boundaries. By coarse‐graining in space and time, we compute the first spatio‐temporal global spectrum of geostrophic circulation from AVISO and NEMO. These spectra show that every length‐scale evolves over a wide range of time‐scales with a consistent peak at ≈200 km and ≈2–3 weeks. Plain Language Summary Traditionally, “eddies” are identified as time‐varying features relative to a background time‐mean flow. As such, “mean” does not imply large length‐scale. Standing eddies or meanders due to topography have little time‐variation, but can have significant energy at small length‐scales that are unresolved and need to be parameterized in coarse climate simulations. Similarly, “eddy” or “time‐varying” do not imply small length‐scale, such as large‐scale motions from Rossby waves or fluctuations of the Kuroshio. Another common method is Fourier analysis in “representative” ocean boxes that cannot capture the circulation's planetary scales. We overcome these limitations thanks to recent advances: (a) a method for calculating spectra by coarse‐graining, (b) properly defining convolutions on the sphere, which “blur” oceanic flow in a way that preserves its underlying symmetries, opening the door for global “wavelet” analysis and, more generally, spatial coarse‐graining, and (c) FlowSieve: an efficient parallel code. We employ coarse‐graining in space‐time to gain new insights into the global oceanic circulation, including how much energy resides in its different spatial structures and how they vary in time. Key Points Coarse‐graining, which disentangles flow concurrently in scale and space, reveals hemispheric asymmetry in mesoscale energy‐per‐area due to boundaries Coarse‐graining spectra of the time‐mean velocity show that most (up to 70%) of its energy resides in “standing” small‐scale eddies <500 km We estimate that ≈25%–50% of total geostrophic energy is at scales smaller than 100 km, and is un(der)‐resolved by pre‐SWOT satellite products

Eleven 40-day long integrations of five different global models with horizontal resolutions of less than 9 km are compared in terms of their global energy spectra. The method of normal-mode function decomposition is used to distinguish between balanced (Rossby wave; RW) and unbalanced (inertia-gravity wave; IGW) circulation. The simulations produce the expected canonical shape of the spectra, but their spectral slopes at mesoscales, and the zonal scale at which RW and IGW spectra intersect differ significantly. The partitioning of total wave energies into RWs an IGWs is most sensitive to the turbulence closure scheme and this partitioning is what determines the spectral crossing scale in the simulations, which differs by a factor of up to two. It implies that care must be taken when using simple spatial filtering to compare gravity wave phenomena in storm-resolving simulations, even when the model horizontal resolutions are similar. In contrast to the energy partitioning between the RWs and IGWs, changes in turbulence closure schemes do not seem to strongly affect spectral slopes, which only exhibit major differences at mesoscales. Despite their minor contribution to the global (horizontal kinetic plus potential available) energy, small scales are important for driving the global mean circulation. Our results support the conclusions of previous studies that the strength of convection is a relevant factor for explaining discrepancies in the energies at small scales. The models studied here produce the major large-scale features of tropical precipitation patterns. However, particularly at large horizontal wavenumbers, the spectra of upper tropospheric vertical velocity, which is a good indicator for the strength of deep convection, differ by factors of three or more in energy. High vertical kinetic energies at small scales are mostly found in those models that do not use any convective parameterisation.

The adsorption, diffusion, and aggregation of methane from coal are often studied based on slit or carbon nanotube models and isothermal adsorption and thermodynamics theories. However, the pore morphology of the slit model involves a single slit, and the carbon nanotube model does not consider the molecular structure of coal. The difference of the adsorption capacity of coal to methane was determined without considering the external environmental conditions by the molecular structure and pore morphology of coal. The study of methane adsorption by coal under single condition cannot reveal its mechanism. In view of this, elemental analysis, FTIR spectrum, XPS electron energy spectrum, 13C NMR, and isothermal adsorption tests were conducted on the semi-anthracite of Changping mine and the anthracite of Sihe Mine in Shanxi Province, China. The grand canonical Monte Carlo (GCMC) and molecular dynamics simulation method was used to establish the coal molecular structure model. By comparing the results with the experimental test results, the accuracy and practicability of the molecular structure model are confirmed. Based on the adsorption potential energy theory and aggregation model, the adsorption force of methane on aromatic ring structure, pyrrole nitrogen structure, aliphatic structure, and oxygen-containing functional group was calculated. The relationship between pore morphology, methane aggregation morphology, and coal molecular structure was revealed. The results show that the adsorption force of coal molecular structure on methane is as follows: aromatic ring structure (1.96 kcal/mol) > pyridine nitrogen (1.41 kcal/mol) > pyrrorole nitrogen (1.05 kcal/mol) > aliphatic structure (0.29 kcal/mol) > oxygen-containing functional group (0.20 kcal/mol). In the long and narrow regular pores of semi-anthracite and anthracite, methane aggregates in clusters at turns and aperture changes, and the adsorption and aggregation positions are mainly determined by the aromatic ring structure, the positions of pyrrole nitrogen and pyridine nitrogen. The degree of aggregation is controlled by the interaction energy and pore morphology. The results pertaining to coal molecular structure and pore morphology on methane adsorption and aggregation location and degree are conducive to the evaluation of the adsorption mechanism of methane in coal.

Background: High Dose Rate (HDR) brachytherapy is an internal radiation therapy method that delivers high-intensity radiation at >12 Gy/hour dose rate. In clinical practice, the dose calculation is often carried out using the TG-43 However, the method does not consider the effects of patient dimensions and tissue heterogeneity. To overcome this challenge, this study proposed the use of energy spectrum analysis of the source model used. Materials and Methods: GEANT4 Monte Carlo simulation was used to build the geometry of Bebig Co-60 A86 source and radiation interaction system. The interaction physics used Penelope with 1.0 × 108 beam on. The scoring region was spherical with radius 20, 30, 40, and 50 cm as well as material variations of water, muscle, and bone. Results: The spectrum in Compton continuum scattering increased along with a reduction in radius and material density, while the opposite effect was observed at the photoelectric peak. The photoelectric peak ratio experienced 2.96 times increment when the radius of the muscle increased from 20 cm to 30 cm. In addition, the particle count experienced an increment as the radius and medium density of the scoring region increased, with linear regression values of 0.83 for bone and 0.91 for the water and muscle. Conclusion: Increasing the radius and medium density led to variations in the height of the energy spectrum in Compton continuum and photoelectric regions. These variations caused an 18.42% increase in particle count when transitioning from 20 cm to 30 cm radius in water.

The FY-3E satellite plasma analyzer marks China’s first detection of the characteristics, occurrence, and development of the typical plasma environment in the dawn–dusk orbit space. It provides data source support for operational space weather alerts and forecasts, helps ensure the in-orbit safety of the satellite, and accumulates space environment detection data for space environment modeling and space physics research. This paper gives a detailed introduction to the detection technology adopted by the FY-3E satellite plasma analyzer. We calibrated its performance through a calibration experiment and then analyzed and compared it with similar instruments in China. It is indicated that the instrument is capable of measuring an ion energy spectrum of 24 eV~32 keV and an electron energy spectrum of 23.7 eV~31.6 keV, its field of view reaches 180° × 90°, and the inversed measurement range of spacecraft absolute potential is better than −30 kV~+30 kV. All these contribute to a notably improved technology for plasma and satellite potential detection of China’s LEO satellites.