Abstract:The long-term atmospheric evolution and ion escape of unmagnetized terrestrial planets under con-tinuous solar wind erosion are fundamental to understanding their habitability,water loss mechanisms,and evolu-tionary pathways.Although Venus and Mars both lack a global intrinsic magnetic field,their ionospheric structures,surface magnetic field distributions,and atmospheric compositions differ significantly,leading to distinct types of induced magnetospheres and ion acceleration environments.Despite extensive observational and modeling efforts,the physical mechanisms governing the differences in their electromagnetic structures,ion dynamics,and escape fluxes remain insufficiently constrained.To address this issue,we develop and employ a unified three-dimensional multi-fluid magnetohydrodynamic(MHD)model to systematically compare the global plasma structures,electric field systems,heavy ion distributions,and escape characteristics of Venus and Mars under solar wind interaction,and further evaluate the performance of Mars four-species single-fluid,four-species multi-fluid,and ten-species multi-fluid models. Our results show that the ion escape processes of both planets are jointly regulated by the solar wind dynamic pressure,Hall electric field,and ionosphere-magnetosphere coupling.Owing to its dense ionosphere and strong photochemical processes,Venus exhibits a pronounced magnetic pileup region,elevated heavy-ion densities,and a nearly symmetric electromagnetic structure.In contrast,Mars is strongly influenced by spatially variable crustal magnetic fields and more prominent Hall effects,which produce complex ion-scale structures and acceleration pathways at the magnetic pileup boundary,dayside plume region,and magnetotail.The Hall electric field contributes a substantially larger fraction of the total electric field at Mars than at Venus,even dominating the local electric field direction in plume source regions and plasma sheet locations,indicating a stronger electromagnetic accelera-tion capability under comparable upstream conditions. Comparisons between simulations and observations show that the ten-species multi-fluid model most accurately reproduces the bow shock and magnetic pileup positions,ionospheric density profiles,local electric field strengths,and overall ion escape rate(～1.4×1025 s-1).The model also reveals a pronounced mass dependence in Martian ion escape:light ions(e.g.,O+)are preferentially accelerated into the magnetotail and dominate tailward escape,where-as heavy ions(e.g.,O+2,CO+2)primarily escape through dayside plume structures.These patterns reflect the com-bined effects of multi-species coupling,Hall physics,and crustal magnetic field geometry. In summary,Hall electric fields,multi-ion coupling,and localized magnetic field structures are identified as key controlling factors that shape the electromagnetic configuration,ion transport pathways,and long-term atmo-spheric loss of unmagnetized terrestrial planets.The findings deepen our understanding of the physical divergence between Venus and Mars and provide new theoretical constraints for modeling atmospheric evolution and assess-ing planetary habitability.

Abstract:Jupiter possesses the strongest intrinsic magnetic field,the fastest rotation rate,the most volcanically active moon(Io),and the strongest radiation belts among all planets in the solar system.Jupiter's radiation belts are primarily composed of electrons,protons,and heavy ions(mainly oxygen and sulfur ions)moving at relativistic speeds.Both the particle flux and energy in these belts significantly exceed those of Earth's radiation belts.As a natural particle accelerator,Jupiter's radiation belts are not only of fundamental importance for understanding basic plasma physics processes,but also directly relevant to trajectory design,radiation protection for missions to the Jovian system,and the assessment of habitability of its moons.Under the combined influence of solar wind,plane-tary rotation,and natural satellites,Jupiter's radiation belts exhibit highly complex spatial structures and dynamic evolution.However,due to a lack of observational data—especially in the core region of the radiation belts—cur-rent understanding remains substantially incomplete.Based on existing researches on Jupiter's radiation belts,this article provides a systematic review of advances in the study of energetic particle environment of Jupiter's radiation belts.It begins by introducing the spatial structure,energy spectrum characteristics,and pitch angle distribution of both electron and ion radiation belts,with comparisons made to the radiation belts of Earth and Saturn.The review further explores the origins,acceleration,and loss mechanisms of energetic particles in Jupiter's radiation belts,and discusses the influence of natural satellites on the evolution of these particles.An overview is also provided of cur-rent empirical models based on observations and progress in numerical modeling based on physical processes.Fi-nally,the paper concludes by analyzing key scientific questions that urgently need to be addressed in current re-search on Jupiter's radiation belts and preliminarily outlines the challenges posed by Jupiter's extreme radiation en-vironment for future exploration missions to the Jovian system.

Abstract:Ring currents,an important current system formed by the azimuthal drift of charged particles in planetary magnetospheres,play a key role in disturbing planetary magnetic fields and driving magnetospheric dy-namics.This paper systematically reviews recent research progress on the basic features and dynamic processes of ring currents around Earth,Mercury,Jupiter,and Saturn.For Earth's ring current,the contribution ratio of oxygen ions to the plasma pressure and energy density during geomagnetic storms significantly increases,and their loss mechanisms(such as charge exchange)have also been further discussed.In addition,the impact of geomagnetic substorms on the overall intensity,time variations,and spatial distributions of ring currents(such as enhancing dusk side ring currents via particle injections)has also been extensively studied.Further analysis confirms that the im-pacts of these two factors are not independent,but have positive relations:the energy density ratio of oxygen ions also increases during geomagnetic substorms.The existence of a ring current around Mercury had not been con-firmed before.However,using observations from the MESSENGER spacecraft and test particle simulations,recent studies have,for the first time,both observationally and theoretically discovered and confirmed the existence of ring currents that are formed by energetic protons orbiting along the Shabansky orbits.The basic characteristics of Mercury magnetic storms during strong solar activity periods are further studied.Research on the ring currents of Jupiter and Saturn relies highly on the datasets.Thanks to the rich data information provided by the Juno and Cas-sini spacecraft,recent research has,on the basis of previous results,obtained further conclusions on the giants'ring current.For Jupiter,the co-rotation characteristics,the dominant plasma component and their proportions,the spa-tial distributions,as well as the overall structure of the current sheet from the Io orbit to near the dawn side mag-netopause have been established.For Saturn,studies have revealed its bowl-shaped ring current structure,ENA fea-tures,and the 11-year variation cycles.Despite these significant advances,many questions about planetary ring cur-rents remain unresolved,including:(1)the causal relationship between a high ratio of oxygen ions and ring current intensification during intense geomagnetic storms;(2)the response of Mercury's ring current to solar wind vari-ations and the specific processes during Mercury's magnetic storms;and(3)the differences in the structure and dy-namics of ring currents among giant planets.Future satellite missions will provide novel observational data for ring current research,driving new breakthroughs in the discovery of planetary ring currents.

Abstract:The polar cusp region serves as a critical gateway for magnetosheath and solar wind plasma to enter planetary magnetospheres,playing a fundamental role in shaping solar wind-magnetosphere interactions.The mor-phology,location,and dynamics of the cusp not only reflect underlying magnetopause reconnection processes but also reveal the diversity of magnetospheric structures across different planetary environments.This paper provides a systematic review and comparative analysis of recent advances in the study of cusp regions at Earth,Saturn,and Jupiter,with a focus on identification criteria,spatial distribution,and formation mechanisms. Studies revealed that,while the cusp regions of these three planets share key microphysical characteristics—such as the injection of magnetosheath-like low-energy electrons(～100 eV),ion energy dispersion from velocity filtering effects,and the presence of auroral hiss emissions—their large-scale spatial distributions and dynamic behaviors differ markedly.At Earth,cusp regions are typically centered near the noon sector,with recon-nection at the magnetopause primarily controlled by the north-south component of the interplanetary magnetic field(IMF).Under southward IMF,reconnection occurs at low latitudes,shifting the cusp equatorward;under north-ward IMF,reconnection shifts to high-latitude lobe regions,moving the cusp poleward. In contrast,Saturn's cusp exhibits periodic latitudinal oscillations modulated by the planet's～10.7-hour rota-tion,reflecting the influence of rapid rotation and internal plasma sources,particularly from Enceladus.These cusp motions are closely linked to planetary period oscillations within Saturn's magnetosphere,with amplitudes excee-ding 1° in latitude.This behavior highlights Saturn's rotation-dominated systems,and presents a dynamic picture distinct from Earth's. Jupiter,meanwhile,displays the most unconventional cusp configuration.Recent Juno observations have shown that its cusp can persist stably in the dusk sector(17-20 MLT),challenging the traditional Earth-based paradigm of a noon-centered cusp.This unique structure arises from Jupiter's complex three-dimensional magneto-spheric topology,shaped by its rapid～9.9-hour rotation and distinct solar wind environment.At Jupiter's orbit(～5 AU),the IMF spiral angle and clock angle approaches±90°,making the dawn-dusk(IMF By component)compon-ent dominant.Consequently,magnetopause reconnection is primarily governed by By of IMF.Jupiter's strong coro-tation electric field further drives a spiral-shaped open flux region,directly responsible for the cusp's duskward dis-placement. Through this cross-planetary comparison,the study highlights a fundamental transition in cusp behavior—from solar wind-dominated control(as at Earth)to increasing dominance by internal magnetospheric dy-namics(as at Jupiter).The findings demonstrate how the balance between planetary rotation and solar wind forcing systematically shapes cusp characteristics across giant planets.This comparative framework not only advances our understanding of magnetospheric processes within the solar system but also provides a foundation for interpreting magnetospheres at ice giants(Uranus and Neptune)and in exoplanetary systems.

Abstract:The exploration of the Moon is an extremely important part of aerospace missions.However,the Moon lacks the shielding of a global magnetic field and atmosphere,leaving it directly exposed to high energy space radiation,which poses non-negligible potential risks to lunar exploration missions.High energy particles from deep space may directly impact personnel or instruments on the lunar surface.Moreover,they react with the lunar regolith to generate a large number of secondary particles—including a significant amount of neutrons that are difficult to shield against—thereby introducing additional radiation risks.The lunar radiation environment is re-latively complex,constrained by multiple factors(such as radiation sources at different times,varying composi-tions and densities of lunar soil,etc.).Therefore,in addition to analyzing data from detectors mounted on space-craft or lunar landers,particle transport simulations tailored to different scenarios are also an important tool.Study-ing the lunar radiation environment is not only a requirement for the smooth execution of lunar exploration mis-sions but also contributes to addressing scientific issues such as analyzing the mechanisms of cosmic rays and the isotopic composition of lunar samples.As a review article,this paper respectively introduces the main sources of high energy particle radiation on the Moon,the mechanisms of interaction between high energy space radiation particles and lunar regolith,the measurement status of high energy particles and radiation doses on the lunar sur-face in recent years,the simulation of the lunar surface radiation environment,and the outlook for future research prospects.

Abstract:Magnetic reconnection,a ubiquitous plasma process in the universe,serves as a key mechanism for explosive energy release in various astrophysical phenomena.It facilitates the rapid conversion of stored magnetic energy into kinetic energy and thermal energy of particles while simultaneously altering magnetic field topologies.Unlike Earth,Mars does not possess a global intrinsic magnetosphere;instead,it features localized crustal magnetic fields,particularly strong in the southern hemisphere.This configuration allows the solar wind to interact directly with the Martian ionosphere through processes like mass loading and ion pickup,forming an induced magneto-sphere comprising structures such as the bow shock,magnetosheath,induced magnetopause,and magnetotail.The interplanetary magnetic field(IMF)can readily penetrate the relatively weak Martian ionosphere,and the extension of its crustal fields to high altitudes results in a highly complex magnetic topology,akin to that of the solar corona,creating ideal conditions for magnetic reconnection to occur.Moreover,the Martian ionosphere contains multiple ion species,including O+2,O+,and CO+2,alongside collisional effects in certain regions,which impart unique cha-racteristics to reconnection events,diverging markedly from the standard collisionless proton-electron reconnec-tion models prevalent in other space environments. This review provides a comprehensive synthesis of observational,theoretical,and numerical advancements in understanding magnetic reconnection within the Martian space environment.We examine reconnection phenomena across key regions:the induced magnetopause/ionopause,the ionosphere interior,the magnetotail,and the mag-netosheath.Observations from missions like the Mars Atmosphere and Volatile EvolutioN(MAVEN)and Tianwen-1 have revealed diverse reconnection signatures,including Hall magnetic fields,high-speed ion jets,ion heating,and topological changes.For instance,at the induced magnetopause,reconnection between draped IMF and anchored ionospheric fields generates sunward jets that drive significant ion escape,with local rates up to 1.0×1024 s-1.In the magnetotail,reconnection events,often in the-E hemisphere,exhibit mass-dependent ion outflows and contribute to bursty oxygen ion escapes,with rates temporarily reaching global levels like 2.4×1024 s-1.With-in the ionosphere,particularly over strong crustal fields,reconnection between various topologies,such as open-open or draped-closed field lines,produces localized accelerations and contributes to phenomena like interloop re-connection and electron flux enhancements. A focal point of this review is the ionospheric mass ejection(IME)triggered by magnetic reconnection,a newly identified process analogous to solar coronal mass ejections(CMEs).In low-beta regions of the ionosphere,reconnection between oppositely directed open field lines ejects plasma cavities with densities dropping by orders of magnitude,accompanied by outflows exceeding Mars'escape velocity(～5 km/s).Analysis of MAVEN data in-dicates IME events occur approximately three times per Martian day,each ejecting about 1.3 kg of oxygen ions,cu-mulatively accounting for an estimated 0.046 mm global equivalent water layer loss over 4.2 billion years.While this contribution appears modest under current conditions,it likely amplified during the early solar system when solar wind densities and magnetic fields were stronger,enhancing atmospheric erosion. Theoretically,we introduce the multi-fluid generalized Ohm's law tailored for multi-ion species reconnection,extending beyond traditional two-fluid models.By nondimensionalizing the equations,we derive inertial lengths for heavy and light ions,revealing stepwise decoupling processes that form multi-scale diffusion regions and modi-fy Hall effects,outflow structures,and dimensionless reconnection rates.Effective mass interpretations explain de-viations in inertial scales compared to proton-electron cases,with heavy ions exhibiting larger scales due to out-ward electric fields from lighter ions.We also discuss collisional influences,which broaden diffusion regions and reduce reconnection efficiency at lower altitudes(<300 km),potentially leading to partially collisional regimes in-volving ion-neutral or ion-ion interactions. These studies not only elucidate energy conversion mechanisms driving Martian atmospheric and water es-cape,a critical factor in the planet's climate evolution and habitability but also advance fundamental reconnection theory.Future multi-point observations from MAVEN and Tianwen-1,coupled with analogies to solar coronal physics,promise deeper insights into this natural laboratory for plasma processes.

Abstract:Mars is the most Earth-like planet in the solar system and one of the most accessible targets for spacecraft exploration.Unlike Earth,Mars lacks a global intrinsic magnetic field and only retains localized crustal magnetic anomalies in the southern hemisphere.This unique characteristic has made Mars a long-standing research focus in planetary science.It is widely believed that early Mars may have hosted a dense atmosphere and stable li-quid water that supported habitable environmental conditions.However,as atmospheric constituents were progress-ively lost to space,Mars eventually evolved into the cold and arid desert-like world observed today.The influence of crustal magnetic fields on atmospheric ion escape has therefore attracted considerable attention.In this study,we review recent advances on the role of Martian crustal fields in regulating ion escape and focus on their distinct ef-fects under different spatial and solar wind conditions. When the crustal magnetic anomalies rotate to the dayside,their dominant effect is to suppress ion escape,re-ducing the global escape rate by approximately 30%-50%.This suppression arises because the closed magnetic field topology blocks solar wind energy input into the ionosphere and constrains radial ion transport.These closed field structures further result in elevated ionospheric densities above the crustal regions,forming swelling"bulges". When the magnetic anomalies rotate to the dawn-dusk and nightside sectors,they primarily enhance ion es-cape.In these regions,magnetic reconnection frequently occurs,rapidly converting stored magnetic energy into particle acceleration.Meanwhile,the open magnetic topology facilitates radial ion transport,and the crustal fields expand the cross-sectional area available for day-to-night ion flow,effectively enhancing tailward ion escape. Recent studies have proposed a dual-effect framework:crustal magnetic fields suppress ion escape at low alti-tudes but enhance escape at higher altitudes.Specifically,at low altitudes,ion fluxes in the southern hemisphere are much lower than those in the north;however,as altitude increases,ion fluxes in the south gradually exceed those in the north.This dual regulation explains why the southern hemisphere exhibits higher fluxes while maintaining a global escape rate comparable to that of the northern hemisphere. In summary,the Martian crustal magnetic field acts simultaneously as a"shield"and an"amplifier"in the ion escape process,and its impact depends on its local position and upstream solar wind conditions.Current interpreta-tions remain inconclusive owing to limitations in single-satellite sampling and uncertainties in numerical modeling.Nonetheless,understanding these mechanisms is crucial for reconstructing the evolutionary history of the Martian atmosphere,evaluating planetary habitability,and predicting atmospheric evolution on terrestrial exoplanets.Fu-ture progress requires coordinated multi-satellite observations and advanced numerical models to quantitatively as-sess the contribution of crustal fields to long-term atmospheric loss and thus better reveal the transformation of Mars from a warm,watery world to the cold and dry planet we observe today.

Abstract:Seismic imaging plays an important role in the discovery of deep discontinuities,mineral explora-tion,oil and gas prospecting and development,as well as geological surveys.Over the past half-century,with the rapid advancement of high-performance computing and advanced data acquisition,seismic imaging methods have undergone an evolution from traditional ray-based migration to wave-equation imaging,and further to least-squares migration(LSM)and full-waveform inversion(FWI)imaging.By solving a linear or nonlinear inversion problem,inversion-based migration estimates a generalized inverse of the subsurface reflectivity model,which overcomes the limitations of conventional adjoint-operator-based migration methods in irregular acquisition,limited-band-width data,and unbalanced illumination.It can significantly enhance imaging resolution and amplitude fidelity.We systematically review the progress and cutting-edge developments of inversion-based migration in exploration seis-mology,especially focusing on the theory and methodology of data-domain,image-domain and intelligent LSMs.Additionally,we describe various regularization and preconditioning strategies for LSM in terms of their mathem-atical principles and practical effectiveness.Finally,we discuss the latest development in nonlinear FWI imaging,offering theoretical and methodological references for high-precision seismic imaging studies.

Abstract:The Earth's radiation belts are regions where high-energy charged particles congregate in near-Earth space.Given that high-energy particles in the radiation belts pose a severe threat to the safety of spacecraft in orbit and astronauts,it is of vital importance to gain a thorough understanding of the spatiotemporal dynamic evolution of radiation belt particles.Data assimilation method can effectively integrate satellite observations with numerical simulation results,thereby enabling the reconstruction of the spatiotemporal evolution process of radiation belt electrons.This paper systematically summarizes the research achievements in data assimilation modeling of the Earth's radiation belt electrons in recent years.First,we provide a detailed introduction to the three-dimensional data assimilative model of outer radiation belt electrons(TDAMORE),which is based on the Kalman filter method.Building on TDAMORE,further research on data assimilation modeling of radiation belt electrons is carried out using observational data from satellites of different orbital types,such as Van Allen Probes,Arase,and FY-4A.This as-similation model fully leverages the respective strengths of satellite observations and numerical models,success-fully reconstructing the short-term and long-term dynamic evolution processes of electrons with different energies and pitch angles in the outer radiation belt region(L=3-7),as well as their response characteristics to geomagnetic activity.Based on the assimilation results,further research on predicting the flux of radiation belt electrons during geomagnetic storms is conducted,and the predictive performance of the model is evaluated.Finally,this paper dis-cusses and looks ahead to the future development directions and potential application scenarios of radiation belt as-similation models.

Abstract:The neotectonic movement is active in Guanzhong Basin,with extensive development of ground fissures and active faults.To solve the problem of uncertain distribution of concealed active faults in urban areas,in this study,active fault detection was carried out in Guanzhong Basin,and the vibroseis shallow reflection seismic technique was used to obtain high signal-to-noise ratio processed profiles,which presented abundant wave group information,obvious characteristics,clear contact relationship and good continuity derived from the dataset,reveal-ing a clear and continuous Quaternary bottom interface.Based on the characteristics of the wave group and the data of the survey area,the internal structure of the Quaternary system and the following strata were divided,the distri-bution of known and hidden faults in the range of the survey line was identified,the fault characteristics and buried depth were analyzed,and the relevant technical problems in practical work were discussed.The results of this artifi-cial reflection seismic detection work show that the seismic method and data processing technology described in this paper are effective and reliable in urban active fault detection,and can effectively identify the plane position and spatial distribution of active faults in hidden areas.

Abstract:The northeastern margin of the Qinghai-Xizang Plateau,as the primary tectonic front accommoda-ting plateau expansion,represents a crucial region for investigating plateau uplift and lateral growth mechanisms.This seismically active boundary zone provides key insights into the generation processes of strong intracontine-tal earthquakes.This study presents a comprehensive analysis of multidisciplinary datasets,including contemporary geodetic measurements,historical seismicity records,and geophysical observations.Through systematic analysis of seismic activity patterns and crustal deformation features in the northeastern Qinghai-Xizang Plateau,we characte-rize:(1)the spatial distribution of crustal strain accumulation,(2)the present-day stress field configuration,and(3)fault slip rates along major active faults.These parameters are further integrated to assess regional seismic poten-tial.Finally,by integrating deep and shallow geophysical observations,this study investigates how tectonic deform-ation patterns constrain the plateau expansion and uplift processes in the northeastern margin.Although the under-lying dynamic mechanisms(including vertically coherent deformation versus lower crustal flow)remain debated in this region,the present findings provide critical constraints on both tectonic deformation processes and strong earth-quake generation mechanisms within the Qinghai-Xizang Plateau.They also provide valuable insights into the mechanisms driving the plateau's uplift and lateral extension.Building upon current understanding of seismic acti-vity and crustal deformation patterns,augmented by enhanced geodetic and seismological monitoring capabilities,future research is poised to:elucidate finer-scale crustal deformation characteristics and their underlying deep dy-namic processes,and quantitatively constrain the mechanical coupling between active fault systems and earthquake nucleation processes.These advances will establish a robust scientific framework for understanding crustal thicken-ing mechanisms,lateral extensional deformation,and seismic hazard assessment across the region,while providing critical insights into the integrated tectonic evolution of the Qinghai-Xizang Plateau.

Abstract:In order to study the specific application effect of gradient guided optimization methods such as gradient method and conjugate gradient method in the full waveform inversion algorithm flow of seismic explora-tion,the full waveform inversion algorithm program is constructed.A variety of optimization algorithms such as Hestenes-Stiefel,Polak-Ribiere-Polyak,Fletcher-Reeves,Conjugate Descent and Dai-Yuan are implemented.The model example experiment is carried out,and the comprehensive and sufficient experimental results are obtained.The research results show that the Conjugate Descent optimization algorithm achieves the best application effect for the Overthrust near-surface velocity model constructed.Although the experimental results may be affected by many factors such as the complexity of the model and the main frequency of the seismic wavelet used in the experiment,the results of this study can provide reference for related work on research ideas and experimental results.

Abstract:On March 19,1962,the Xinfengjiang Reservoir in Heyuan City,Guangdong Province,induced an M6.1 earthquake as it approached its first full-capacity impoundment peak.This event stands as one of the largest reservoir-induced earthquakes recorded in China and one of the few globally exceeding magnitude 6.Since this mainshock,moderate and small earthquakes have persisted within the reservoir area,characterized by high fre-quency and widespread distribution.The seismogenic mechanism remains unclear due to the complex geological structure of the reservoir area,featuring intersecting faults and well-developed joints and fractures.While most exi-sting research focuses on earthquakes with M≥4.0,systematic studies on M3-4 events are still lacking.To reveal the primary seismogenic structures and the complex genesis mechanism of reservoir earthquakes in this region,this paper conducts a systematic study on source parameters of moderate and small earthquakes occurring between 2008 and 2023. We employed the double-difference earthquake relocation method to relocate events of M≥1.0.The Cut and Paste(CAP)method was applied to invert for focal mechanism solutions and source depths of events with M≥3.0.Additionally,we obtained the regional stress field with the damped regional-scale stress tensor inversion method.Furthermore,to overcome the ambiguity of the two nodal planes in focal mechanism solutions and identify the true causative fault,rupture directivity parameters for events of M≥3.0 were inverted using the source time-frequency signature method. The results indicate distinct spatial heterogeneity in the seismicity of the Xinfengjiang Reservoir area,with the overall seismogenic structures exhibiting a NW-SE trend.Current earthquake types near Xichang Town and Yukeng Village are predominantly strike-slip,while the dam area is dominated by normal faulting.The overall stress field in the reservoir area aligns with that of South China,characterized by a NW-SE oriented maximum prin-cipal compressive stress(σ1).However,local stress field variations exist,showing an approximately 10° clockwise rotation in the orientations of the maximum and minimum principal stresses from south to north.The R-values are approximately 0.26 and 0.22 near Xichang Town,0.32 near Yukeng Village,and 0.1 and 0.06 in the dam area,in-dicating a regional stress state biased towards extension,which is more pronounced near the dam. Combined with the analysis of rupture directivity parameters,it is revealed that the Xichang seismic zone con-tains two intersecting faults at approximately 10 km depth-a NW-trending dextral strike-slip fault and a NEE-trending sinistral strike-slip fault;the Yukeng Village area features a pre-existing NNW-trending sinistral strike-slip fault at 8-10 km depth;the Laohuilong Village area exhibits a NW-trending fracture at about 5 km depth;the north-ern dam area is characterized by a NW-trending strike-slip fault at～10 km depth intersecting with the Renzishi Fault;the southern dam area contains a WNW-trending strike-slip fault at 6-10 km depth;the southeastern dam area presents a NEE-trending sinistral strike-slip fault at～10 km depth intersecting with the Heyuan Fault.Compre-hensive research indicates that current seismic activities in the Xinfengjiang Reservoir area are jointly influenced by regional tectonic background and long-term reservoir impoundment,leading to reactivation or kinematic transform-ation of pre-existing faults,thereby triggering frequent small earthquake swarms.These findings provide important seismological evidence for understanding the mechanisms of reservoir-induced seismicity and assessing regional seismic hazards.

Abstract:Exosphere is an essential component of the atmospheres of terrestrial bodies.Its structure and vari-ability hold significant scientific values for understanding planetary material loss,atmospheric evolution,and habit-ability.This paper systematically reviews the progress in the study of the exospheres of terrestrial bodies over the past 60 years,covering their formation mechanisms,observational and simulation methods,and variabilities.In terms of origin,the exospheres can be classified into three types:lower atmosphere-origin exospheres,surface-ori-gin exospheres,and interior-driven exospheres.After their formations,exospheric particles also undergo various loss processes,keeping the structures of the exospheres in a state of dynamic evolution.Spectroscopic and mass spectrometric measurements are the primary observational methods for studying exospheres,providing essential data for analyzing their structures and variabilities.The classical Chamberlain model remains the most widely used approach for deriving exospheric density distributions.Subsequent developments,including the Boltzmann trans-port equation and Monte Carlo simulations,further incorporate the effects of particle energization below the exo-base,making them particularly advantageous for studying deviations from local thermodynamic equilibrium and the escape of high-energy non-thermal particles.The variabilities of the exospheres are driven by both internal and external factors,including external drivers such as solar cycle,solar flares,physical and dynamical processes in the lower atmosphere,and gravitational interactions in binary systems,as well as internal processes such as geological activities.These factors significantly alter the structural characteristics of the exospheres by affecting the genera-tion and loss of exospheric particles.By reviewing relevant research findings,this paper aims to provide valuable references for further improving the theoretical framework of exosphere formation,elucidating its dynamic proper-ties,and investigating its impact on planetary atmospheric evolution and habitability.

Abstract:As the main carrier of mass migration,exchange and circulation in the Earth's hydrosphere cycle processes,the redistribution of land water plays a vital role in climate change and human activities.The time-vary-ing(or time-lapse)4D surface and satellite gravity,and deformation observations have a revolutionary impact on the study of spatiotemporal changes in terrestrial water storage(TWS),but they still face challenges in terms of reso-lution and sensitivity of hydrological signal monitoring.This study introduces the scientific background and main geophysical observation methods for studying TWS changes.Focusing on gravity and deformation monitoring of global/regional spatiotemporal responses of hydrological mass signals as the goal,we sequentially expound on the basic principles,data models,processing techniques,inversion methods and driving factors involved in recent years.Based on application examples,the basic ideas and processes of estimating TWS using surface gravity(con-tinuous and absolute),satellite gravity(GRACE)and GNSS observations are given in detail,and then the problems and technical bottlenecks that may exist in gravity and deformation solutions so far are discussed.Finally,we briefly look forward to the application prospects of monitoring water mass migration and the underlying causes based on gravity and deformation technology.This study provides a variety of perspectives for in-depth understand-ing of the TWS changes and its driving factors,and has reference value for the development of Hydrogeophysics.

Abstract:Climatic aridity-humidity variations on orbital timescales are crucial for understanding the Earth's climate system response mechanisms.Investigating the relationship between orbital-scale eccentricity cycles and aridity-humidity changes helps clarify the mechanisms by which Earth's climate system responds to astronomical forcing.This paper systematically summarizes how eccentricity drives regional moisture variations by modulating precession-induced seasonal solar radiation distribution,supported by case studies from diverse regions.When Earth's orbit approaches a perfect circle(i.e.,eccentricity is close to zero),the influence of precession on the distri-bution of solar radiation is minimal,thereby weakening its capacity to modulate the climate system.In contrast,during periods of higher eccentricity,when the orbit is more elliptical,precession significantly enhances the season-al contrasts and alters the spatial and temporal distribution of climate zones.Moreover,precession determines the timing and geographic position of perihelion.For example,when Northern Hemisphere summer occurs near perihe-lion,that region receives stronger summer insolation while winter insolation decreases,intensifying seasonal tem-perature differences and exerting profound effects on precipitation and evaporation.By synthesizing geological and climatic records from multiple representative regions across Eurasia,this study analyzes how different areas re-spond to eccentricity-driven hydroclimate variability.Most existing studies suggest that high eccentricity periods are generally associated with more humid environments.This is mainly attributed to stronger seasonal contrasts un-der high eccentricity conditions,which enhance monsoonal circulation and increase precipitation in monsoon-domi-nated regions such as East Asia,South Asia,and Africa.In addition,eccentricity may exert indirect control over re-gional hydroclimate patterns through its influence on high-latitude ice sheet size and the seasonal distribution of solar radiation.However,due to variations in latitude,dominant climate systems,the type and resolution of geolo-gical records,and whether the region is influenced by ice sheets,the effects of eccentricity on regional climate are highly complex and spatially heterogeneous.For instance,in areas dominated by the westerlies or located in mid-latitudes,climate changes may show an anti-phase relationship with eccentricity cycles.In these regions,high ec-centricity may enhance processes where evaporation exceeds precipitation,strengthen monsoonal activity while suppressing the Mongolian anticyclone,or alter the position and intensity of the westerlies,leading to hydroclimate responses that are opposite to the general trend of eccentricity variation.And during low eccentricity periods,the modulation of precession amplitude is weak,resulting in a relatively stable climate that may favor vegetation growth and the maintenance of ecosystems.Therefore,when exploring the mechanisms by which eccentricity regu-lates regional hydroclimate change,it is important to avoid the mechanical application of a single region's climate response pattern.Instead,one must comprehensively consider the modulation of precession amplitude by eccentri-city,as well as key regional factors such as geographic location,paleogeographic setting,geological record type,and the developmental stage of ice sheets,to conduct more targeted and systematic analyses.

Abstract:Oasis agriculture in arid regions persistently faces dual challenges of water scarcity and secondary soil salinization,making accurate acquisition of spatiotemporal soil moisture distribution characteristics critical for sustaining agricultural development.Geophysical detection methods such as ground penetrating radar(GPR)have become viable approaches for mesoscale soil moisture monitoring.However,conventional GPR methods suffer performance degradation in high-conductivity saline soils due to electromagnetic wave attenuation and scattering.Additionally,existing GPR early-time signal studies are predominantly limited to homogeneous or low-loss media,lacking systematic validation in oasis farmland environments characterized by high salinity and spatial heterogen-eity,which severely constrains the widespread application of this method in saline soil moisture inversion.This study constructs a multi-scale saline soil model based on elliptical random media,integrating forward simulations with field experiments in Xinjiang oasis cotton fields to quantitatively compare the performance of antenna fre-quencies(250 MHz and 1000 MHz)and early-time signal indices including carrier frequency amplitude(CFA)and average envelope amplitude(AEA)in saline soil moisture inversion.The results demonstrate that:(1)Both early-time signal methods maintain stable inversion accuracy(R2>0.60)in saline soils with conductivities up to 0.36 S/m,confirming the feasibility of GPR early-time signal methods for quantitative soil moisture inversion in highly saline environments;(2)The accuracy of saline soil moisture inversion based on early-time signals is highly sensitive to antenna frequency and medium heterogeneity,with the 250 MHz low-frequency antenna exhibiting su-perior depth adaptability and anti-interference capability for monitoring the 0-30 cm plough layer,while the 1000 MHz antenna shows heightened sensitivity to scattering effects from small-scale surface heterogeneities;(3)The CFA index demonstrates higher sensitivity to dielectric constant variations under low soil moisture condi-tions(<15%),whereas the AEA index exhibits enhanced stability in high moisture environments(>20%).This study proposes an optimized strategy for GPR early-time signal saline soil moisture inversion indices tailored to different degrees of soil heterogeneity and moisture conditions,and validates through field experiments the practi-cal applicability of 250 MHz antennas combined with CFA and AEA indices in oasis farmland environments,providing innovative technical support for precision water-salt management in arid oasis agriculture.

Abstract:The Antarctic ice sheet plays an increasingly significant regulating role in the global climate system,where geothermal heat flow(GHF)serves as a critical indicator of basal thermal conditions.Understanding its spa-tial distribution is essential for studying its dynamic evolution.Current GHF measurements in Antarctica remain limited to merely 52 data points due to extreme cold geological conditions and prohibitive drilling costs.Existing GHF estimates based on geological and geophysical data exhibit substantial uncertainties and fail to account for non-linear heat transfer processes in the bedrock.Deep learning algorithms demonstrate superior predictive capabilities for sparse data interpolation by capturing coupled relationships between GHF and multi-source data features.We develop a deep neural network(DNN)integrated with a high-dimensional uncertainty quantification framework to predict Antarctic GHF distribution.Utilizing over 4000 global GHF observations and 22 geological and geophysi-cal features(including crustal thickness,gravity/magnetic anomalies,and Moho depth)as training data,we validate the model against known GHF points in Australia and Antarctica.The uncertainty quantification method reorga-nizes the training dataset through correlation,sensitivity,and principal component analysis,combined with DNN model to determine optimal GHF distribution.Prediction results reveal the GHF range of 24-103 mW/m2 with a mean value of 60.1 mW/m2,showing a 10.05%error relative to measured data.The Gamburtsev Subglacial Moun-tains exhibit significant high GHF anomalies(50-74 mW/m2).Uncertainty quantification confirms high confid-ence levels for these GHF predictions.Our model successfully interprets spatial heterogeneity characteristics of Antarctic crustal thermal structure,and the prediction results can be further applied to model Antarctic-scale ice sheet dynamics or thermodynamics,provide reliable data support for studies on ice sheet motion and subglacial lake distribution.