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.

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.

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.

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.