Edge detection represents a critical task in potential field data interpretation and is extensively utilized for detecting faults, contacts, and other linear geological structures. However, conventional methods are constrained by several limitations, including inadequate balancing of signals with varying amplitude intensities, dispersed detection results, and insufficient suppression of spurious signals. To overcome these challenges, we propose an improved edge detection method, designated as the hyperbolic tangent (TANH) function with Gaussian envelope constraints on the total gradient modulus tilt angle (THASTG). The THASTG method is formally defined as a tilt angle approach based on the total gradient modulus, incorporating dual constraints through a Gaussian envelope and a TANH function. We initially conducted comparative analyses between the THASTG and established methods by using complex models simulating three distinct geological scenarios, thereby validating the feasibility of the methodology. Subsequent application to real gravity data from the South China Sea region demonstrated that compared with conventional techniques, THASTG yields enhanced structural detail, improved boundary resolution, and superior noise suppression. This method effectively suppresses noise interference and successfully avoids the introduction of spurious boundaries while maintaining consistency with previously documented major tectonic features. This study provides high-resolution structural constraints for the South China Sea region, delineates the offshore extension of the Red River Fault system, and accurately maps the continent–ocean boundary configuration. Our results demonstrate that the proposed methodology provides an effective tool for precise structural characterization and in-depth analysis of geodynamic evolution processes.

To understand energy transfer during sudden stratospheric warming (SSW) events in the middle atmosphere, the 2023 SSW is studied by using the analysis tools of the multiscale window transform (MWT) and MWT-based localized energetics analysis and theory of canonical transfer (MS-ECT). The energy transfer in the mesosphere is diagnosed and compared with that in the stratosphere. The energy fields are first reconstructed onto three scale windows: a large-scale window, an SSW-scale window, and a synoptic-scale window. Results showed that the work done by pressure (pressure flux) plays a critical role in coupling the mesosphere and stratosphere during SSW events. The cross-scale energy transfer (canonical transfer) of available potential energy is always directed from the large-scale to the SSW-scale window, indicating the central role of baroclinic instability in both the stratosphere and mesosphere. Comparative analysis with the 2012–2013 SSW event revealed the consistent presence of baroclinic instability across both events. However, the 2023 event exhibited significantly stronger energy transfer magnitudes in the mesosphere. These results highlight the consistent role of baroclinic instability and pressure flux in mediating cross-scale energy transfer during SSWs, providing a clearer understanding of stratosphere–mesosphere coupling.

Understanding rupture transfer across fault junctions is critical for interpreting complex multi-fault earthquakes. For the 2023 M_w 7.8 Kahramanmaraş event, we construct three dynamic rupture models constrained by surface fault traces, relocated aftershocks, kinematic slip inversions, near-field strong-motion records, and GPS data to distinguish among potential nucleation sites along the East Anatolian Fault (EAF). Our simulations reveal that although the final slip distributions are insensitive to the precise nucleation point owing to complex fault geometry, the dynamic conditions required for rupture initiation on the EAF differ significantly. Nucleation at the triple junction is facilitated by dynamic Coulomb stress triggering from the Narlı branch fault. Although the supershear rupture velocity is different along the Narlı branch fault of Model 1 and Model 3, both models support nucleation at the triple junction. In contrast, nucleation at 9 km southwest of the triple junction requires artificial stress concentrations, as shown in Model 2. Model 3 shares the same stress concentration along the EAF; however, its near-P-wave supershear speed along the branch fault narrows the Mach cone and directly impedes nucleation to the southwest. All the models show good correspondence with the near-field seismogram and GPS observations. Additionally, we compare the source time functions of the three models with the U.S. Geological Survey result, which imply that the near-P-wave supershear speed along the branch fault is less likely. Our results suggest the triple junction is the most likely nucleation site, and although the 9 km southwest of the triple junction is still possible, it requires highly localized initial stress concentrations.

Modeling the mass density of the thermosphere is essential for understanding the upper atmospheric dynamics and for supporting satellites and the space station. Such modeling has traditionally relied on either empirical approaches or first-principles physics-based frameworks. The empirical models are computationally efficient with relatively lower accuracy, whereas the physics-based models are more accurate with the cost of computation time. In this study, a data-driven deep learning model based on a modified U-Net architecture is proposed to estimate the global thermospheric mass density at altitudes of 100 to 500 km. This model directly utilizes input features including time, spatial coordinates, geomagnetic indices, the F_10.7 solar flux, and the solar wind speed. To improve the model performance, we have introduced three main components: a gated recurrent unit-enhanced attention mechanism for spatially adaptive feature refinement, a height-adaptive normalization technique to mitigate altitude-induced bias, and a hybrid loss function combining mean absolute error with Laplacian loss to preserve both the global structure and fine-scale details. The proposed model achieves accuracy comparable to physics-based models such as the Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM), with percentage errors typically below 5%, while the simulation time has been dramatically reduced from tens of minutes to a few seconds. This framework provides an efficient and accurate tool for reconstructing the global thermospheric density and can potentially be utilized for real-time estimation of the thermosphere density under varying geomagnetic and solar conditions.

The Kelvin–Helmholtz (KH) instability serves as an important process for transporting the solar wind mass and energy into the Earth’s magnetosphere. However, energy conversion and energy transport at the vortices driven by the KH instability have not been investigated in detail thus far. Here, using high-resolution data from the Magnetospheric Multiscale (MMS) spacecraft, we compare characteristics of energy conversion and energy flux densities between a linear and a nonlinear KH vortex. We find that the linear KH vortex is acting as a generator region (∫J·E < 0, where J is the current density and E is the electric field) whereas the nonlinear KH vortex is a load region (∫J·E > 0). The energy flux densities increase significantly at the trailing edge of KH vortices. At the linear KH vortex, energy transfer is equally contributed by enthalpy, ion kinetic, and Poynting fluxes, whereas in the nonlinear case, the energy is mainly transported in the form of the Poynting flux and electron kinetic energy and heat fluxes are negligible. These results help us better understand the role of KH vortices in energy conversion and transport at the Earth’s magnetopause.

In this study, we investigate the source and dynamics of a mesoscale gravity wave (MGW) observed over northern China. On January 12, 2010, an OH airglow imager at the Xinglong station (40.2°N, 117.4°E) detected an MGW propagating from southwest to northeast, consistent with the background wind direction. The wave exhibited a horizontal wavelength of 125 ± 7.6 km, an observed period of 25 ± 3.2 min, and a phase speed of 83 ± 12.4 m/s. The momentum flux and the energy flux of the MGW were approximately 24.93 m²/s² and 1.08 × 10⁻⁵ W/m², respectively, from the airglow imaging observation. During propagation, wave breaking generated secondary ripples with wavelengths of 5–12 km. These ripples were likely caused by wind shear, as measured by the Doppler meteor radar at Shisanling (40.3°N, 116.2°E). According to OH emission profiles from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, the height of the OH airglow layer was ~81 km during the MGW propagation event. A separate northwestward-propagating small-scale gravity wave with a wavelength of ~35 km was also observed. The backward ray-tracing analysis conducted with European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis data indicated that the jet system near the Tibetan Plateau served as the source for the MGW.

The distribution and transport of carbon dioxide (CO₂) in the middle and upper atmosphere are closely linked to atmospheric dynamical processes, but the influence of planetary waves on CO₂ transport remains unclear. This study aims to investigate the impact of quasi-2-day waves (Q2DWs) on CO₂ transport in the stratosphere–mesosphere during the sudden stratospheric warming (SSW) period. On the basis of data assimilation (DA) using the Whole Atmosphere Community Climate Model (WACCM) + Next-generation Ensemble Data Assimilation System (NEDAS) from December 2018 to February 2019, we used the transformed Eulerian mean framework to conduct a diagnostic analysis on Q2DW propagation and amplification. Additionally, we identified unstable regions in the stratosphere between 60°N and 80°N. This configuration facilitates the amplification of Q2DWs through enhanced baroclinic and barotropic instabilities. The results demonstrate that the dynamic features exhibit distinct propagation and amplification characteristics. We also found distinct Q2DWs in CO₂ at the middle latitudes of the southern hemisphere, which were mainly induced by the Q2DWs in temperature. Further analysis showed that the anomalous vertical motion during the SSW period could lead to the enhancement of CO₂ vertical gradients, which also contributed to the strengthening of Q2DWs in CO₂.

The formation of spicules on the solar surface is poorly understood. In the present investigation, we propose a mechanism that provides an explanation for this phenomenon. The squeeze of the enhanced downflow region in the intergranular lanes by oscillation results in an initial narrow, high-speed upward flow with a velocity on the order of several kilometers per second and a width on the order of 10 km. The underlying physics principle is the same as in the design of an anti-tank weapon, called a “shaped charge”. The life of a spicule is divided into two stages. The first stage is mechanical driving by the pressure gradient at its base; the second stage is electromagnetic driving. Dynamo action in the early lifetime of a spicule plays an important role in the transfer of mechanical energy to magnetic energy. The subsequent Fermi acceleration is responsible for the energy transfer from magnetic energy to thermal energy and kinetic energy. Depending on the strength of the ambient magnetic field, the formation of type I spicules (strong case) and type II spicules (weak case) can be naturally explained in this frame setting, which is one of the merits of our proposed mechanism. The variation in temperature along the height is consistent with prior observation-based models.

Electron dynamics plays a crucial role in the evolution of the Martian ionosphere. However, the adiabatic process, a classical mechanism for modulating electron energy and pitch-angle distributions, has not been reported in this environment. Utilizing data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we present evidence of a decrease in electron perpendicular energy predominantly driven by betatron cooling in the Martian ionosphere. The phenomenon was identified within closed magnetic field lines at the edge of the crustal magnetic fields, a region characterized by a convoluted magnetic field topology comprising both closed and open lines. The observed cooling of 10–150 eV electrons with a power-law distribution, enhancing the cigar distribution, was quantitatively reproduced by an adiabatic model. Our study may promote the understanding of electron dynamics in the Martian ionosphere.

A rocket launch can induce large-scale atmospheric disturbances, which have mainly been investigated in previous studies by using measurements of total electron content. In this study, we report the perturbation in very low frequency (VLF) transmitter signals triggered by a rocket launch event, which, unlike total electron content measurements, is directly related to the D-region ionosphere. The perturbation in VLF measurements typically occurred ~9 min after liftoff, resulting in an amplitude change of up to 2.82 dB, and it had a common period of ~3.5–7 min. Moreover, the perturbation consisted of two isolated pulses, a feature notably different from previous measurements. Given the close correlation between the rocket launch and the VLF measurements, as well as the similarity between different propagation paths, these perturbations were likely caused by shock acoustic waves generated during the rocket launch because the periods were similar.