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.

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.

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.

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.

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.

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 influence of topography on rotating fluids may exceed conventional expectations. Here, we numerically examine viscous incompressible flows induced by sidewall topography, confined within a modified cylinder that rotates rapidly about its central vertical axis and precesses about another axis. To investigate specific flow patterns and boundary-interior correspondences, the cylindrical sidewall is modified by adding a vertical fin-type barrier extending all the way from the bottom to the top. The fully nonlinear Navier−Stokes equations with precessional forcing are solved in this modified cylindrical geometry, using a mixed finite element method. Numerical results show that the introduction of sidewall topography significantly alters the precessionally driven flow, particularly at high precession rates. While the primary dynamics associated with inertial wave propagation persist, rich vortical structures and turbulence emerge. Interestingly, the barrier does not invariably suppress the kinetic energy density; when its height approaches the cylinder radius under strong precession, the kinetic energy density even exceeds that of the cylinder case without a barrier. Such an anomalous enhancement of kinetic energy may offer new insights into how precession-driven flows over topography could contribute to sustaining long-lived planetary magnetic fields, including that of the early Moon.

Whistler-mode waves are ubiquitous in space environments and constitute a key mechanism for energy transfer and transformation. The near-1 Hz narrowband whistler-mode waves are commonly observed in lunar space. However, the generation mechanism of narrowband 1 Hz whistler-mode waves in the lunar environment, where no global magnetosphere or permanent bow shock exists, remains an open question. This study examines 1 Hz waves in the lunar environment by analyzing 12 years (2012–2023) of ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun) mission data (across an entire solar cycle). The spatial distribution, spectral characteristics, and polarization properties of these waves are investigated alongside their dependence on upstream solar wind parameters and lunar magnetic anomalies. The results reveal that 1 Hz waves are predominantly observed in the solar wind near the Moon, with clear dawn–dusk and north–south asymmetries. Wave amplitudes range from 0.03 to 1 nT, and approximately 90% of the events demonstrate no direct magnetic connectivity to the Moon. Importantly, wave amplitude shows a positive correlation with the solar wind dynamic pressure (P_dyn) and the total interplanetary magnetic field (B_total) and an inverse correlation with the Alfvén Mach number (M_A), underscoring the influence of upstream conditions on wave properties. Our findings reveal that the majority of waves occur on unconnected field lines, indicating a more complex generation and propagation scenario than previously assumed. Furthermore, wave properties are quantitatively shown to be strongly modulated by upstream solar wind conditions. These results provide critical statistical constraints for future studies of wave generation in the unique plasma environment of an unmagnetized body.

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.