Astrophysics and Space Science最新文献

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) is set to revolutionize astronomy by generating an unprecedented petascale dataset. However, the success of its primary science goals, such as precision cosmology with weak lensing, is critically threatened by atmospheric turbulence, which blurs images and can systematically corrupt the faint cosmological signals. The sheer volume of LSST data—approximately 20 terabytes per night—renders classical iterative deconvolution methods computationally infeasible, while generic deep learning approaches often lack the physical guarantees necessary for high-precision science. This creates an urgent need for a fast, robust, and physically-grounded deconvolution framework. To meet this challenge, we introduce a deep learning model that synergistically combines a dual-domain architecture with physics-informed learning. Our U-Net model incorporates a Fast Fourier Transform (FFT) layer at its input, enabling it to directly “see” and correct the frequency-dependent signature of atmospheric blurring. We train the model with a hybrid loss function that enforces both structural realism, via a Point Spread Function (PSF) consistency term, and photometric accuracy, through a flux conservation constraint. Our final model, HF-UNet, produces good reconstructions on realistically degraded images, accurately recovering key galaxy morphological parameters with exceptional fidelity, achieving low Root Mean Square Error (RMSE) values, for instance, 0.05 for ellipticity and 3.37 for half-light radius with the proposed HF-UNet model. Crucially, it exhibits superior robustness when tested on data with mismatched PSF profiles and varying noise levels. This work presents a scientifically reliable deconvolution framework, offering an enabling technology essential for realizing the full scientific potential of the LSST.

The Viking mission identified both cold and hot electron populations in the auroral zone, enabling electron acoustic waves (EAWs) whose nonlinear dissipative interactions are believed to contribute significantly to broadband electrostatic noise (BEN). In this study, we examine the dissipative dynamics of EAWs in collisionless, unmagnetized plasmas using an effective viscosity model. The wave evolution is governed by a Higher Order Boussinesq–Burgers (HOBB) equation that incorporates enhanced nonlinear and dispersive effects. Analytical and numerical investigations reveal that when dissipation dominates over dispersion, the soliton structure transitions into a shock wave. In the weakly dissipative regime, the HOBB equation is solved using the Hirota bilinear method to obtain multi-soliton solutions. A detailed phase-space analysis, Poincaré sections, and near-zero Lyapunov exponents confirm the presence of quasiperiodic behaviour. Energy-based stability criteria show that the solutions remain stable when dissipative effects outweigh dispersive and nonlinear steepening influences. The bipolar electric potential structures predicted by the HOBB equation are analyzed for auroral plasma parameters relevant to Viking observations. The calculated amplitudes and durations of solitary structures show good agreement with measured BEN waveforms. These results demonstrate that the HOBB model successfully captures the interplay of nonlinearity, dispersion, and dissipation, offering a plausible mechanism for the generation of BEN in space plasmas.

While trying to arrive at the four-picket pulse shape, the author of this work accidently found a very interesting result. Specifically, it is found that not only four-picket pulse can be formed from combination of two or more Maxwell distributions but additionally several non-Maxwellian distributions can be generated. This result is very attractive and physically acceptable. Because, systems having two types of distributions will go to a third state that is non-equilibrium state, meaning that two Maxwellian distributions will give a third distribution and so on. Our results are significant for plasma systems connected to external energy source such as solar wind.

This research investigates the geoeffectiveness of interplanetary magnetic field configurations by analyzing 203 geomagnetic storm events recorded between 1995 and 2015. The study systematically categorizes events into five intensity levels: quiet, weak, moderate, intense, and severe, to evaluate how different polarity configurations and flux rope configurations influence geomagnetic activity. Utilizing an extensive methodology, we employed correlation analysis and superposed epoch analysis on 17 parameters extracted from OMNI/NASA hourly datasets. The investigation focused on identifying how specific magnetic configurations impact geomagnetic storm characteristics, with special attention to the Disturbance Storm-Time Index (Dst). The findings reveal nuanced variations in geoeffectiveness across magnetic configurations. Configurations were stratified into two primary groups, with Group 1 (S, SN, SNN, SNS) demonstrating notably higher geomagnetic responsiveness. Notably, the SNS configuration emerged as the most geoeffective, accounting for 37% of intense storms and exhibiting an extended main phase lasting 48 hours. Conversely, Group 2 configurations (N, NS, NSS, NSN) generally displayed reduced geoeffectiveness, contributing to 30% of quiet storms and merely 3% of severe storms. However, the NSS configuration presented an intriguing anomaly, characterized by the lowest negative Dst value and an unprecedented 96-hour recovery phase, attributed to its distinctive two-step main phase storm. Flux rope configurations also demonstrated differential impacts, with the (F^{+}) rotation being particularly geoeffective, contributing to 11% of severe storms. We further uncovered a remarkably strong correlation between the dawn-dusk electric field (Ey) and (Dst_{min}) in the NSS configuration, registering a correlation coefficient of -0.95.

The triple collision represents a fundamental singularity in the equations of motion for the three-body problem. Building upon previously identified triple collision orbits with equal masses, we employ the Clean Numerical Simulation (CNS) and the numerical continuation method to compute triple collision orbits for the free-fall three-body system with unequal masses. We first identify triple collision orbits for the three-body system where two bodies have unit mass, while the third body has various masses. Additionally, we extend our computation to obtain the triple collision orbits for the three-body problem with different masses. Numerical evidence is presented to demonstrate the asymptotic behavior of triple collision orbits with unequal masses. Our findings have potential inspiration for the study of the dynamical characteristic around the singularity of three-body systems.

Coronal mass ejections (CMEs) are major drivers of space weather disturbances, and their deflection from the radial direction critically affects their potential impact on Earth. While the influence of the surrounding magnetic field in guiding CME trajectories is well established, accurately predicting non-radial propagation remains a challenge. In this work, we introduce and compare recently developed techniques for analyzing the early deflection of eruptive events. We revisit a largely deflected prominence-CME event of 2010 December 16 using an improved tracking framework and a new application of the topological path method. Our results suggest the deflection of the eruption is dominated by the channeling of the magnetic field lines. This study offers new physical insight into CME guidance mechanisms and validates the predictive capability of the topological path, highlighting its potential as a diagnostic tool for estimating the propagation direction of strongly deflected events.

We review the observational evidence for the empirical upper luminosity limit in the Hertzsprung-Russell Diagram. We discuss its impact on our understanding of the evolution of the most massive stars, the importance of the high mass loss events that shape the upper limit, and the instabilities that may tigger the eruptions in stars close to their Eddington Limit.

Solar flares, intense solar eruptions, discharge electromagnetic radiation and energetic particles that may have major consequences for both space weather and Earth’s atmospheric conditions. Therefore, developing high-precision forecasting models is crucial. In this paper, we propose a solar flare prediction model, which integrates the Swin Transformer with a TCN augmented by a global attention mechanism, named SwinTCN-Att, for predicting whether ≥C- and ≥M-class flare events will erupt in the solar active regions (ARs) in the next 24 hours. We collected magnetogram data from solar ARs obtained from the Space Weather Helioseismic and Magnetic Imager Active Region Patch (SHARP) dataset, spanning from May 2010 to December 2019, and selected 16 magnetic field feature parameters from the SHARP data. The construction of the model is carried out in two stages: first, the spatial characteristics of the magnetogram are captured using the Swin Transformer; next, these spatial features are integrated with 16 magnetic field parameters. Temporal features are then derived using TCN with a global attention mechanism to predict solar flares. Then, following model training and testing, we evaluated performance using five different assessment metrics, with the True Skill Statistic (TSS) serving as the primary evaluation metric. The results show that the TSS scores achieved were 0.825 ± 0.042 for ≥C-class flares and 0.879 ± 0.025 for ≥M-class flares, marking a significant improvement over previous models. These results demonstrate that the proposed SwinTCN-Att model effectively integrates relevant solar flare information, combines the strengths of both individual models, and captures solar flare evolution features, achieving superior predictive performance.

In this paper, we present a comprehensive validation of bottomside electron density profile (EDP) thickness (B0) and shape (B1) parameters derived through least-square fitting of FORMOSAT-7/COSMIC-2 radio occultations with the coincident-colocated Digisonde EDPs at 24 locations spanning equatorial, low-, and mid-latitude regions and the default bottomside modeling option in the latest edition of the International Reference Ionosphere model (IRI-2020). These parameters are essential descriptors of the ionospheric bottomside morphology, which are critical for characterizing the vertical structure of the ionosphere and are influenced by solar flux, geomagnetic activity, and space weather dynamics. Leveraging a large dataset from COSMIC-2, we employed rigorous quality constraints through visual inspections and defined exclusion criteria to identify the most representative profiles for investigating the diurnal, seasonal, and longitudinal variations of the parameters as a function of local time during the period from 2020 to 2022, corresponding to the ascending phase of solar cycle 25. The results demonstrate that COSMIC-2 derived B0 and B1 parameters have better agreement with Digisonde observations than those predicted by IRI-2020, highlighting the significance of COSMIC-2 profile parameters towards improvement in empirical ionosphere models.

In this work, we studied the helium-induced collisional excitation of the radical ion HCl⁺. Our work focuses on calculating two-dimensional potential energy surfaces (PES) to study the interaction due to the collision between HCl⁺ and He, and on analyzing the influence of the isotopic effect on cross sections and collision rates. For Ab initio calculations of PES (^{2}A^{prime }) and (^{2}A^{prime prime }) of HCl⁺(X(^{2}Pi ))-He complex, we used the RCCSD(T)-F12 method with cc-pVQZ-F12 basis sets. These surfaces have been fitted using the Reproducing Kernel Hilbert Space (RKHS) method and were submitted to the close-coupling approach in order to work out the inelastic integral cross sections. Collision cross sections taking into account the fine structures of HCl⁺ have been performed for kinetic energies up to 3500 cm⁻¹ and the thermal excitation rates for kinetic temperatures varying from (4K) up to 400 K. It appears that the difference in the cross section and collisional rate cofficients for the H³⁵Cl⁺ and H³⁷Cl⁺ colliding with He was found to be negligeable. In contrast, a significant difference in effective cross-sections and collision rates between HCl⁺-He and DCl⁺-He was observed to the extent that it is impossible to make estimation of collision rates of deuterated species from those of the hydrogenated species.