Impact craters are important for understanding the evolution of lunar geologic and surface erosion rates,among other functions.However,the morphological characteristics of these micro impact craters are not obvious an...Impact craters are important for understanding the evolution of lunar geologic and surface erosion rates,among other functions.However,the morphological characteristics of these micro impact craters are not obvious and they are numerous,resulting in low detection accuracy by deep learning models.Therefore,we proposed a new multi-scale fusion crater detection algorithm(MSF-CDA)based on the YOLO11 to improve the accuracy of lunar impact crater detection,especially for small craters with a diameter of<1 km.Using the images taken by the LROC(Lunar Reconnaissance Orbiter Camera)at the Chang’e-4(CE-4)landing area,we constructed three separate datasets for craters with diameters of 0-70 m,70-140 m,and>140 m.We then trained three submodels separately with these three datasets.Additionally,we designed a slicing-amplifying-slicing strategy to enhance the ability to extract features from small craters.To handle redundant predictions,we proposed a new Non-Maximum Suppression with Area Filtering method to fuse the results in overlapping targets within the multi-scale submodels.Finally,our new MSF-CDA method achieved high detection performance,with the Precision,Recall,and F1 score having values of 0.991,0.987,and 0.989,respectively,perfectly addressing the problems induced by the lesser features and sample imbalance of small craters.Our MSF-CDA can provide strong data support for more in-depth study of the geological evolution of the lunar surface and finer geological age estimations.This strategy can also be used to detect other small objects with lesser features and sample imbalance problems.We detected approximately 500,000 impact craters in an area of approximately 214 km2 around the CE-4 landing area.By statistically analyzing the new data,we updated the distribution function of the number and diameter of impact craters.Finally,we identified the most suitable lighting conditions for detecting impact crater targets by analyzing the effect of different lighting conditions on the detection accuracy.展开更多
Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which...Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which is governed by five terms:conductivity,heating,cooling,adiabatic expansion,and advection.The derivations mentioned are strongly dependent on the collision cross section between electrons and other particles(e.g.,neutrals,ions).It is notable that the momentum transfer cross sections between electrons and neutrals have been updated in recent decades.However,the widely used momentum average collision cross sections between electrons and neutrals,derived from the momentum transfer cross sections,are collected in studies dating back nearly half a century.Therefore,it becomes imperative to revise the momentum average collision cross sections relevant to astrophysical contexts,based on the latest studies.In this study,we summarize the momentum average collision cross sections of 13 species common in planetary atmospheres:H,H_(2),He,O,CH_(4),H_(2)O,CO,N_(2),O_(2),Ar,CO_(2),N_(2)O,and NO_(2).All results are derived from the latest studies concerning the electron-neutral collision cross section and are compared with previous studies.Furthermore,we present a comparison of the derived total electron-neutral collision frequency at Mars between this study and previous studies.Prominent differences in the total electron-neutral collision frequency between this and prior studies support the significance of updating the momentum average collision cross section between electrons and neutrals in studying the planetary atmospheres.展开更多
The full constellation of Chinese Global Navigation Satellite System(GNSS)Bei Dou-3 has been deployed completely and started fully operational service.In addition to providing global Positioning,Navigation and Timing(...The full constellation of Chinese Global Navigation Satellite System(GNSS)Bei Dou-3 has been deployed completely and started fully operational service.In addition to providing global Positioning,Navigation and Timing(PNT)services,the Bei Dou-3 satellites transmissions can also be used as the sources of illumination for Earth Observation(EO)with a bistatic radar configuration.This innovative EO concept,known as GNSS reflectometry(GNSS-R),allows to measure the Earth surface characteristics at high resolution via the reflected L-band radar signals collected by a constellation of small,low cost and low Earth orbiting satellites.For the first time in orbit,earth reflected Bei Dou-3 signal has been detected from the limited sets of raw data collected by the NASA’s Cyclone GNSS(CYGNSS)constellation.The feasibility of spaceborne Bei Dou-3 reflections on two typical applications,including sea surface wind and flooding inundation detection,has been demonstrated.The methodology and results give new strength to the prospect of new spaceborne GNSS-R instruments and missions,which can make multi-GNSS reflectometry observations available to better capture rapidly changing weather systems at better spatio-temporal scales.展开更多
In-flight calibration of the ze ro offset is crucial for ensuring high-precision measure ment of the spaceborne fluxgate magnetomete r.Tianwen-1 is China’s first Mars mission,and its orbiter will re main out of the s...In-flight calibration of the ze ro offset is crucial for ensuring high-precision measure ment of the spaceborne fluxgate magnetomete r.Tianwen-1 is China’s first Mars mission,and its orbiter will re main out of the solar wind for tens of days each year.Previous in-flight calibration methods might not be suitable for this orbiter during such a period.Recently,a new method was proposed by Wang GQ(2022 b),which we refer to as the Wang method Ⅱ for ease of description.Here,we test the performance of this method in the Martian magnetosheath by using magnetic field data measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) spacecraft.We find that the accuracy of the Wang method Ⅱ is affected by the number of magnetic field subinterval events,the eigenvalues of the minimum variance analysis for each event,and the position of the spacecraft in the magnetosheath.The estimated zero offset varies over a period of~27 days and has a 57.3% probability of accuracy within 2.0 nT.After being smoothed with a temporal window of 27 days,the ze ro offset has a 48.4%(99.3%) probability of accuracy within 1.0(2.0) nT.Our tests suggest that the Wang method Ⅱ provides an option for the Tianwen-1 orbiter to perform in-flight calibration when the orbiter remains out of the solar wind for an extended pe riod of time.展开更多
The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to ...The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.展开更多
Kinetic-scale magnetic holes(KSMHs)are structures characterized by a significant magnetic depression with a length scale on the order of the proton gyroradius.These structures have been investigated in recent studies ...Kinetic-scale magnetic holes(KSMHs)are structures characterized by a significant magnetic depression with a length scale on the order of the proton gyroradius.These structures have been investigated in recent studies in near-Earth space,and found to be closely related to energy conversion and particle acceleration,wave-particle interactions,magnetic reconnection,and turbulence at the kineticscale.However,there are still several major issues of the KSMHs that need further study—including(a)the source of these structures(locally generated in near-Earth space,or carried by the solar wind),(b)the environmental conditions leading to their generation,and(c)their spatio-temporal characteristics.In this study,KSMHs in near-Earth space are investigated statistically using data from the Magnetospheric Multiscale mission.Approximately 200,000 events were observed from September 2015 to March 2020.Occurrence rates of such structures in the solar wind,magnetosheath,and magnetotail were obtained.We find that KSMHs occur in the magnetosheath at rates far above their occurrence in the solar wind.This indicates that most of the structures are generated locally in the magnetosheath,rather than advected with the solar wind.Moreover,KSMHs occur in the downstream region of the quasi-parallel shock at rates significantly higher than in the downstream region of the quasi-perpendicular shock,indicating a relationship with the turbulent plasma environment.Close to the magnetopause,we find that the depths of KSMHs decrease as their temporal-scale increases.We also find that the spatial-scales of the KSMHs near the subsolar magnetosheath are smaller than those in the flanks.Furthermore,their global distribution shows a significant dawn-dusk asymmetry(duskside dominating)in the magnetotail.展开更多
Nuclear astrophysics is a rapidly developing interdisciplinary feld of research that has received extensive attention from the scientifc community since the midtwentieth century.Broadly,it uses the laws of extremely s...Nuclear astrophysics is a rapidly developing interdisciplinary feld of research that has received extensive attention from the scientifc community since the midtwentieth century.Broadly,it uses the laws of extremely small atomic nuclei to explain the evolution of the universe.Owing to the complexity of nucleosynthesis processes and our limited understanding of nuclear physics in astrophysical environments,several critical astrophysical problems remain unsolved.To achieve a better understanding of astrophysics,it is necessary to measure the cross sections of key nuclear reactions with the precision required by astrophysical models.Direct measurement of nuclear reaction cross sections is an important method of investigating how nuclear reactions infuence stellar evolution.Given the challenges involved in measuring the extremely low crosssections of nuclear reactions in the Gamow peak and preparing radioactive targets,indirect methods,such as the transfer reaction,coulomb dissociation,and surrogate ratio methods,have been developed over the past several decades.These are powerful tools in the investigation of,for example,neutron-capture(n,r)reactions with short-lived radioactive isotopes.However,direct measurement is still preferable,such as in the case of reactions involving light and stable nuclei.As an essential part of stellar evolution,these low-energy stable nuclear reactions have been of particular interest in recent years.To overcome the diffculties in measurements near or deeply within the Gamow window,the combination of an underground laboratory and high-exposure accelerator/detector complex is currently the optimal solution.Therefore,underground experiments have emerged as a new and promising direction of research.In addition,to better simulate the stellar environment in the laboratory,research on nuclear physics under laser-driven plasma conditions has gradually become a frontier hotspot.In recent years,the CIAE team conducted a series of distinctive nuclear astrophysics studies,relying on the Jinping Underground Nuclear Astrophysics platform and accelerators in Earth’s surface laboratories,including the Beijing Radioactive Ion beam Facility,as well as other scientifc platforms at home and abroad.This research covered nuclear theories,numerical models,direct measurements,indirect measurements,and other novel approaches,achieving great interdisciplinary research results,with high-level academic publications and signifcant international impacts.This article reviews the above research and predicts future developments.展开更多
Four key reactions, 12C(, )13O, 13C(, n)16O, 25Mg(p, )26Al and 19F(p, )16O, will be studied for the first time within or near the astrophysical relevant energy regions (Gamow window) at Jinping Underground laboratory ...Four key reactions, 12C(, )13O, 13C(, n)16O, 25Mg(p, )26Al and 19F(p, )16O, will be studied for the first time within or near the astrophysical relevant energy regions (Gamow window) at Jinping Underground laboratory for Nuclear Astrophysics (JUNA)[1], which will take the advantage of the ultra-low background of China JinPing underground Laboratory (CJPL), high current accelerator based on ECR source and a highly sensitive detection system.展开更多
Metalens technology has been applied extensively in miniaturized and integrated infrared imaging systems.However,due to the high phase dispersion of unit structures,metalens often exhibits chromatic aberration,making ...Metalens technology has been applied extensively in miniaturized and integrated infrared imaging systems.However,due to the high phase dispersion of unit structures,metalens often exhibits chromatic aberration,making broadband achromatic infrared imaging challenging to achieve.In this paper,six different unit structures based on chalcogenide glass are constructed,and their phase-dispersion parameters are analyzed to establish a database.On this basis,using chromatic aberration compensation and parameterized adjoint topology optimization,a broadband achromatic metalens with a numerical aperture of 0.5 is designed by arranging these six unit structures in the far-infrared band.Simulation results show that the metalens achieves near diffraction-limited focusing within the operating wavelength range of 9−11μm,demonstrating the good performance of achromatic aberration with flat focusing efficiency of 54%−58%across all wavelengths.展开更多
The increasing complexity of on-orbit tasks imposes great demands on the flexible operation of space robotic arms, prompting the development of space robots from single-arm manipulation to multi-arm collaboration. In ...The increasing complexity of on-orbit tasks imposes great demands on the flexible operation of space robotic arms, prompting the development of space robots from single-arm manipulation to multi-arm collaboration. In this paper, a combined approach of Learning from Demonstration (LfD) and Reinforcement Learning (RL) is proposed for space multi-arm collaborative skill learning. The combination effectively resolves the trade-off between learning efficiency and feasible solution in LfD, as well as the time-consuming pursuit of the optimal solution in RL. With the prior knowledge of LfD, space robotic arms can achieve efficient guided learning in high-dimensional state-action space. Specifically, an LfD approach with Probabilistic Movement Primitives (ProMP) is firstly utilized to encode and reproduce the demonstration actions, generating a distribution as the initialization of policy. Then in the RL stage, a Relative Entropy Policy Search (REPS) algorithm modified in continuous state-action space is employed for further policy improvement. More importantly, the learned behaviors can maintain and reflect the characteristics of demonstrations. In addition, a series of supplementary policy search mechanisms are designed to accelerate the exploration process. The effectiveness of the proposed method has been verified both theoretically and experimentally. Moreover, comparisons with state-of-the-art methods have confirmed the outperformance of the approach.展开更多
This article aims to provide a comprehensive analysis of the role and development prospects of direct satellite-to-phone technology in the global communication landscape.It explores the importance,current development ...This article aims to provide a comprehensive analysis of the role and development prospects of direct satellite-to-phone technology in the global communication landscape.It explores the importance,current development status,key technical challenges,future directions,and countermeasures of this technology from multiple dimensions.The article explains the significance and necessity of direct satellite-to-phone technology in the global communication field,discusses its development background and importance as one of the key technologies in the 6G era,and outlines the research objectives,methodology,and structure of the paper.Additionally,the article reviews and analyzes the development history of direct satellite-to-phone technology on a global scale,discusses the key technical points in achieving this technology,and predicts its potential role and development direction in future communication systems from the perspective of 6G network architecture.It also explores new application scenarios and service models that may emerge from technological advancements,as well as their impact on future communication networks.The development history of direct satellite-to-phone technology and its role in current and future communication networks are emphasized,highlighting its value in promoting global communication infrastructure construction.The article also proposes improvement suggestions for existing issues and points out future research directions.展开更多
The Spectral Imaging Corona Graph(SICG) serves as the optical observation equipment of E-corona in the Chinese Meridian Project Phase II, which aims at monitoring the initial source of solar activities. For the purpos...The Spectral Imaging Corona Graph(SICG) serves as the optical observation equipment of E-corona in the Chinese Meridian Project Phase II, which aims at monitoring the initial source of solar activities. For the purpose of indepth exploration and space weather forecast in the full chain of Sun–Earth space, SICG is designed to work at two wavelengths of 637.4 and 530.3 nm in the quasi-simultaneous observation mode. Thus, the photometric calibration is more challenging to guarantee accurate scientific data of SICG. Two solar photometers are specially developed to match the observing wavelengths and make the photoelectronic conversion traceable. Correspondingly, the calibration process selects the solar disk center as the brightness reference, which compensates for the photometric losses along the atmospheric transmission path. This study derives the calibration coefficients from the two photometers for the E-coronal brightness processing in real time. By modeling aerosol absorption and scattering and comparing with continuous flat-field observation, the photometric calibration of SICG is evaluated with deviations of 2.1% and 2.3% at 637.4 nm and 530.3 nm, respectively. Based on this, the evolution speed of a multitemperature coronal loop was analyzed, facilitating further research into the physical mechanisms of coronal mass ejections.展开更多
1 Summary Mathematical modeling has become a cornerstone in understanding the complex dynamics of infectious diseases and chronic health conditions.With the advent of more refined computational techniques,researchers ...1 Summary Mathematical modeling has become a cornerstone in understanding the complex dynamics of infectious diseases and chronic health conditions.With the advent of more refined computational techniques,researchers are now able to incorporate intricate features such as delays,stochastic effects,fractional dynamics,variable-order systems,and uncertainty into epidemic models.These advancements not only improve predictive accuracy but also enable deeper insights into disease transmission,control,and policy-making.Tashfeen et al.展开更多
The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective lens.Due to the random accumulation of dust on the lens surfaces,it is challenging to ...The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective lens.Due to the random accumulation of dust on the lens surfaces,it is challenging to monitor this type of stray light and no application can be used for its real-time monitor in the past.In this study,we provide a system and method to overcome this issue,and these have been applied to the Spectral Imaging CoronaGraph(SICG)of the Chinese Meridian Project.The method is based on the relation between the sizes of dust particles and its stray light level at the imaging plane established in the laboratory and the relation between the real size of dust particles and the occupancies on the imaging plane.To monitor the stray light levels accounted for by dusts,one needs only an image of the objective lens that can be provided by the auxiliary imaging system that specially comes with SICG.Our tests show that the errors of the method are less or about 2%,giving a strong confidence in its accuracy.It provides a handy tool to monitor the dust level of the objective lens of SICG and has significantly improved the efficiency of the pipeline of stray light control.展开更多
Exohiss are broadband,structureless whistler-mode waves outside the plasmapause.In our work,using the data sets detected by the EMFISIS suite aboard Van Allen Probe A,from 1st January 2013 to 30th June 2017,the exohis...Exohiss are broadband,structureless whistler-mode waves outside the plasmapause.In our work,using the data sets detected by the EMFISIS suite aboard Van Allen Probe A,from 1st January 2013 to 30th June 2017,the exohiss waves are categorized among two types based on the direction of Poynting flux:unidirectional exohiss,and bidirectional exohiss waves.It seems that most exohiss waves are bidirectional,which are mainly distributed on the dayside.Compared to the hiss waves within the plasmasphere,the amplitude of bidirectional exohiss waves on the prenoon side increase very little with the enhancement of geomagnetic activity.Through the analysis of suprathermal electron flux associated with geomagnetic activity,this suggests that the waves may undergo very strong Landau damping during intense geomagnetic activity.On the other hand,the unidirectional exohiss waves are mainly distributed on the afternoon side,and the largest unidirectional exohiss waves are observed during the highest levels of substorm activity.展开更多
In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. U...In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.展开更多
The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cos...The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cosmic ray albedo neutron decay(CRAND),radial diffusion, and local acceleration have been considered principal sources of electrons, whereas protons are predominantly from CRAND and solar protons. In this article, lightning-induced neutrons from Earth's upper atmosphere are suggested as a possible source of protons and electrons in the inner radiation belt. These terrestrial neutrons can contribute to the inner belt population by undergoing nuclear decay. Several approaches are proposed and discussed to evaluate the potential contribution of lightning-induced neutrons to the inner belt, including magnitude estimation, Monte Carlo simulations, and in situ observations. This article discusses some avenues of further study to determine the contribution of lightning-induced neutrons to the inner radiation belt.展开更多
A 50 mm balloon-borne white-light coronagraph(BBWLC)to observe white-light solar corona over the altitude range from 1.08 R_(⊙)to 1.50 R_(⊙)has recently been indigenously developed by Yunnan Observatories in collabo...A 50 mm balloon-borne white-light coronagraph(BBWLC)to observe white-light solar corona over the altitude range from 1.08 R_(⊙)to 1.50 R_(⊙)has recently been indigenously developed by Yunnan Observatories in collaboration with Shandong University(in Weihai)and Changchun Institute of Optics,Fine Mechanics and Physics,which will significantly improve the ability of China to detect and measure the inner corona.On 2022 October 4,its first scientific flight took place at the Dachaidan area in Qinghai province of China.We briefly describe the BBWLC mission including its optical design,mechanical structure,pointing system,the first flight and results associated with the data processing approach.Preliminary analysis of the data shows that BBWLC imaged the K-corona with three streamer structures on the west limb of the Sun.To further confirm the coronal signals obtained by BBWLC,comparisons were made with observations of the K-coronagraph of the High Altitude Observatory and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory.We conclude that BBWLC eventually observed the white-light corona in its first scientific flight.展开更多
Recent observations have demonstrated the capability of mapping the solar coronal magnetic field using the technique of coronal seismology based on the ubiquitous propagating Alfvénic/kink waves through imaging s...Recent observations have demonstrated the capability of mapping the solar coronal magnetic field using the technique of coronal seismology based on the ubiquitous propagating Alfvénic/kink waves through imaging spectroscopy.We established a magnetohydrodynamic model of a gravitationally stratified open magnetic flux tube,exciting kink waves propagating upwards along the tube.Forward modeling was performed to synthesize the Fe XIII 1074.7 and 1079.8 nm spectral line profiles,which were then used to determine the wave phase speed,plasma density,and magnetic field with seismology method.A comparison between the seismologically inferred results and the corresponding input values verifies the reliability of the seismology method.In addition,we also identified some factors that could lead to errors during magnetic field measurements.Our results may serve as a valuable reference for current and future coronal magnetic field measurements based on observations of propagating kink waves.展开更多
This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches,in relation to the interplanetary magnetic field(IMF)and ionospheric convection geometry.A total of 11,946 patch events were ide...This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches,in relation to the interplanetary magnetic field(IMF)and ionospheric convection geometry.A total of 11,946 patch events were identified by Defense Meteorological Satellite Program(DMSP)F16 during the years 2011 to 2022.A temperature ratio of ion/electron temperature(T_(i)/T_(e))<0.68 is recommended to define a hot patch in the Southern Hemisphere,otherwise it is defined as a cold patch.The cold and hot patches have different dependencies on IMF clock angle,while their dependencies on IMF cone angle are similar.Both cold and hot patches appear most often on the duskside,and the distribution of cold patches gradually decreases from the dayside to the nightside,while hot patches have a higher occurrence rate near 14 and 21 magnetic local time(MLT).Moreover,we compared the key plasma characteristics of polar cap cold and hot patches in the Southern and Northern Hemispheres.The intensity of the duskside upward field-aligned current of patches in the Southern Hemisphere(SH)is stronger than that in the Northern Hemisphere(SH),which may be due to the discrepancy in conductivities between the two hemispheres,caused by the tilted dipole.In both hemispheres,the downward soft-electron energy flux of the dawnside patches is significantly greater than that of the duskside patches.展开更多
基金the National Key Research and Development Program of China(Grant No.2022YFF0711400)which provided valuable financial support and resources for my research and made it possible for me to deeply explore the unknown mysteries in the field of lunar geologythe National Space Science Data Center Youth Open Project(Grant No.NSSDC2302001),which has not only facilitated the smooth progress of my research,but has also built a platform for me to communicate and cooperate with experts in the field.
文摘Impact craters are important for understanding the evolution of lunar geologic and surface erosion rates,among other functions.However,the morphological characteristics of these micro impact craters are not obvious and they are numerous,resulting in low detection accuracy by deep learning models.Therefore,we proposed a new multi-scale fusion crater detection algorithm(MSF-CDA)based on the YOLO11 to improve the accuracy of lunar impact crater detection,especially for small craters with a diameter of<1 km.Using the images taken by the LROC(Lunar Reconnaissance Orbiter Camera)at the Chang’e-4(CE-4)landing area,we constructed three separate datasets for craters with diameters of 0-70 m,70-140 m,and>140 m.We then trained three submodels separately with these three datasets.Additionally,we designed a slicing-amplifying-slicing strategy to enhance the ability to extract features from small craters.To handle redundant predictions,we proposed a new Non-Maximum Suppression with Area Filtering method to fuse the results in overlapping targets within the multi-scale submodels.Finally,our new MSF-CDA method achieved high detection performance,with the Precision,Recall,and F1 score having values of 0.991,0.987,and 0.989,respectively,perfectly addressing the problems induced by the lesser features and sample imbalance of small craters.Our MSF-CDA can provide strong data support for more in-depth study of the geological evolution of the lunar surface and finer geological age estimations.This strategy can also be used to detect other small objects with lesser features and sample imbalance problems.We detected approximately 500,000 impact craters in an area of approximately 214 km2 around the CE-4 landing area.By statistically analyzing the new data,we updated the distribution function of the number and diameter of impact craters.Finally,we identified the most suitable lighting conditions for detecting impact crater targets by analyzing the effect of different lighting conditions on the detection accuracy.
基金the National Natural Science Foundation of China through Grants 42261160643,42441806,42241114,and 42304166supported by the open project funded by the Key Laboratory of Geospace Environment,Chinese Academy of Sciences,University of Science and Technology of China.
文摘Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which is governed by five terms:conductivity,heating,cooling,adiabatic expansion,and advection.The derivations mentioned are strongly dependent on the collision cross section between electrons and other particles(e.g.,neutrals,ions).It is notable that the momentum transfer cross sections between electrons and neutrals have been updated in recent decades.However,the widely used momentum average collision cross sections between electrons and neutrals,derived from the momentum transfer cross sections,are collected in studies dating back nearly half a century.Therefore,it becomes imperative to revise the momentum average collision cross sections relevant to astrophysical contexts,based on the latest studies.In this study,we summarize the momentum average collision cross sections of 13 species common in planetary atmospheres:H,H_(2),He,O,CH_(4),H_(2)O,CO,N_(2),O_(2),Ar,CO_(2),N_(2)O,and NO_(2).All results are derived from the latest studies concerning the electron-neutral collision cross section and are compared with previous studies.Furthermore,we present a comparison of the derived total electron-neutral collision frequency at Mars between this study and previous studies.Prominent differences in the total electron-neutral collision frequency between this and prior studies support the significance of updating the momentum average collision cross section between electrons and neutrals in studying the planetary atmospheres.
基金supported in part by the Spanish Ministry of Economy and Competitiveness and EU/FEDER(ESP201570014-C2-2-R)the International Science and Technology Cooperation Projects of Shanghai(No.17220730600)the ESA-MOST China Dragon5 Program(ID.58070)。
文摘The full constellation of Chinese Global Navigation Satellite System(GNSS)Bei Dou-3 has been deployed completely and started fully operational service.In addition to providing global Positioning,Navigation and Timing(PNT)services,the Bei Dou-3 satellites transmissions can also be used as the sources of illumination for Earth Observation(EO)with a bistatic radar configuration.This innovative EO concept,known as GNSS reflectometry(GNSS-R),allows to measure the Earth surface characteristics at high resolution via the reflected L-band radar signals collected by a constellation of small,low cost and low Earth orbiting satellites.For the first time in orbit,earth reflected Bei Dou-3 signal has been detected from the limited sets of raw data collected by the NASA’s Cyclone GNSS(CYGNSS)constellation.The feasibility of spaceborne Bei Dou-3 reflections on two typical applications,including sea surface wind and flooding inundation detection,has been demonstrated.The methodology and results give new strength to the prospect of new spaceborne GNSS-R instruments and missions,which can make multi-GNSS reflectometry observations available to better capture rapidly changing weather systems at better spatio-temporal scales.
基金supported by the Shenzhen Science and Technology Research Program (JCYJ20210324121412034)the Guangdong Basic and Applied Basic Research Foundation (2022A1515011698)supported by the NASA (National Aeronautics and Space Administration) Mars Exploration Program
文摘In-flight calibration of the ze ro offset is crucial for ensuring high-precision measure ment of the spaceborne fluxgate magnetomete r.Tianwen-1 is China’s first Mars mission,and its orbiter will re main out of the solar wind for tens of days each year.Previous in-flight calibration methods might not be suitable for this orbiter during such a period.Recently,a new method was proposed by Wang GQ(2022 b),which we refer to as the Wang method Ⅱ for ease of description.Here,we test the performance of this method in the Martian magnetosheath by using magnetic field data measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) spacecraft.We find that the accuracy of the Wang method Ⅱ is affected by the number of magnetic field subinterval events,the eigenvalues of the minimum variance analysis for each event,and the position of the spacecraft in the magnetosheath.The estimated zero offset varies over a period of~27 days and has a 57.3% probability of accuracy within 2.0 nT.After being smoothed with a temporal window of 27 days,the ze ro offset has a 48.4%(99.3%) probability of accuracy within 1.0(2.0) nT.Our tests suggest that the Wang method Ⅱ provides an option for the Tianwen-1 orbiter to perform in-flight calibration when the orbiter remains out of the solar wind for an extended pe riod of time.
基金supported by the NSFC(Grant Nos 42130204 and 42188101)the Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the support of the Tencent Foundation.
文摘The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.
基金the National Natural Science Foundation of China(grants 41731068,41774153,41941001,41961130382,41431072,and 41704169)Royal Society NAF\R1\191047the PRODEX program managed by ESA in collaboration with the Belgian Federal Science Policy Office.
文摘Kinetic-scale magnetic holes(KSMHs)are structures characterized by a significant magnetic depression with a length scale on the order of the proton gyroradius.These structures have been investigated in recent studies in near-Earth space,and found to be closely related to energy conversion and particle acceleration,wave-particle interactions,magnetic reconnection,and turbulence at the kineticscale.However,there are still several major issues of the KSMHs that need further study—including(a)the source of these structures(locally generated in near-Earth space,or carried by the solar wind),(b)the environmental conditions leading to their generation,and(c)their spatio-temporal characteristics.In this study,KSMHs in near-Earth space are investigated statistically using data from the Magnetospheric Multiscale mission.Approximately 200,000 events were observed from September 2015 to March 2020.Occurrence rates of such structures in the solar wind,magnetosheath,and magnetotail were obtained.We find that KSMHs occur in the magnetosheath at rates far above their occurrence in the solar wind.This indicates that most of the structures are generated locally in the magnetosheath,rather than advected with the solar wind.Moreover,KSMHs occur in the downstream region of the quasi-parallel shock at rates significantly higher than in the downstream region of the quasi-perpendicular shock,indicating a relationship with the turbulent plasma environment.Close to the magnetopause,we find that the depths of KSMHs decrease as their temporal-scale increases.We also find that the spatial-scales of the KSMHs near the subsolar magnetosheath are smaller than those in the flanks.Furthermore,their global distribution shows a significant dawn-dusk asymmetry(duskside dominating)in the magnetotail.
基金National Natural Science Foundation of China(Nos.12435010)National Key R&D Program of China(No.2022YFA1602301)。
文摘Nuclear astrophysics is a rapidly developing interdisciplinary feld of research that has received extensive attention from the scientifc community since the midtwentieth century.Broadly,it uses the laws of extremely small atomic nuclei to explain the evolution of the universe.Owing to the complexity of nucleosynthesis processes and our limited understanding of nuclear physics in astrophysical environments,several critical astrophysical problems remain unsolved.To achieve a better understanding of astrophysics,it is necessary to measure the cross sections of key nuclear reactions with the precision required by astrophysical models.Direct measurement of nuclear reaction cross sections is an important method of investigating how nuclear reactions infuence stellar evolution.Given the challenges involved in measuring the extremely low crosssections of nuclear reactions in the Gamow peak and preparing radioactive targets,indirect methods,such as the transfer reaction,coulomb dissociation,and surrogate ratio methods,have been developed over the past several decades.These are powerful tools in the investigation of,for example,neutron-capture(n,r)reactions with short-lived radioactive isotopes.However,direct measurement is still preferable,such as in the case of reactions involving light and stable nuclei.As an essential part of stellar evolution,these low-energy stable nuclear reactions have been of particular interest in recent years.To overcome the diffculties in measurements near or deeply within the Gamow window,the combination of an underground laboratory and high-exposure accelerator/detector complex is currently the optimal solution.Therefore,underground experiments have emerged as a new and promising direction of research.In addition,to better simulate the stellar environment in the laboratory,research on nuclear physics under laser-driven plasma conditions has gradually become a frontier hotspot.In recent years,the CIAE team conducted a series of distinctive nuclear astrophysics studies,relying on the Jinping Underground Nuclear Astrophysics platform and accelerators in Earth’s surface laboratories,including the Beijing Radioactive Ion beam Facility,as well as other scientifc platforms at home and abroad.This research covered nuclear theories,numerical models,direct measurements,indirect measurements,and other novel approaches,achieving great interdisciplinary research results,with high-level academic publications and signifcant international impacts.This article reviews the above research and predicts future developments.
文摘Four key reactions, 12C(, )13O, 13C(, n)16O, 25Mg(p, )26Al and 19F(p, )16O, will be studied for the first time within or near the astrophysical relevant energy regions (Gamow window) at Jinping Underground laboratory for Nuclear Astrophysics (JUNA)[1], which will take the advantage of the ultra-low background of China JinPing underground Laboratory (CJPL), high current accelerator based on ECR source and a highly sensitive detection system.
文摘Metalens technology has been applied extensively in miniaturized and integrated infrared imaging systems.However,due to the high phase dispersion of unit structures,metalens often exhibits chromatic aberration,making broadband achromatic infrared imaging challenging to achieve.In this paper,six different unit structures based on chalcogenide glass are constructed,and their phase-dispersion parameters are analyzed to establish a database.On this basis,using chromatic aberration compensation and parameterized adjoint topology optimization,a broadband achromatic metalens with a numerical aperture of 0.5 is designed by arranging these six unit structures in the far-infrared band.Simulation results show that the metalens achieves near diffraction-limited focusing within the operating wavelength range of 9−11μm,demonstrating the good performance of achromatic aberration with flat focusing efficiency of 54%−58%across all wavelengths.
基金co-supported by the National Natural Science Foundation of China(No.12372045)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023B1515120018)the Shenzhen Science and Technology Program,China(No.JCYJ20220818102207015).
文摘The increasing complexity of on-orbit tasks imposes great demands on the flexible operation of space robotic arms, prompting the development of space robots from single-arm manipulation to multi-arm collaboration. In this paper, a combined approach of Learning from Demonstration (LfD) and Reinforcement Learning (RL) is proposed for space multi-arm collaborative skill learning. The combination effectively resolves the trade-off between learning efficiency and feasible solution in LfD, as well as the time-consuming pursuit of the optimal solution in RL. With the prior knowledge of LfD, space robotic arms can achieve efficient guided learning in high-dimensional state-action space. Specifically, an LfD approach with Probabilistic Movement Primitives (ProMP) is firstly utilized to encode and reproduce the demonstration actions, generating a distribution as the initialization of policy. Then in the RL stage, a Relative Entropy Policy Search (REPS) algorithm modified in continuous state-action space is employed for further policy improvement. More importantly, the learned behaviors can maintain and reflect the characteristics of demonstrations. In addition, a series of supplementary policy search mechanisms are designed to accelerate the exploration process. The effectiveness of the proposed method has been verified both theoretically and experimentally. Moreover, comparisons with state-of-the-art methods have confirmed the outperformance of the approach.
文摘This article aims to provide a comprehensive analysis of the role and development prospects of direct satellite-to-phone technology in the global communication landscape.It explores the importance,current development status,key technical challenges,future directions,and countermeasures of this technology from multiple dimensions.The article explains the significance and necessity of direct satellite-to-phone technology in the global communication field,discusses its development background and importance as one of the key technologies in the 6G era,and outlines the research objectives,methodology,and structure of the paper.Additionally,the article reviews and analyzes the development history of direct satellite-to-phone technology on a global scale,discusses the key technical points in achieving this technology,and predicts its potential role and development direction in future communication systems from the perspective of 6G network architecture.It also explores new application scenarios and service models that may emerge from technological advancements,as well as their impact on future communication networks.The development history of direct satellite-to-phone technology and its role in current and future communication networks are emphasized,highlighting its value in promoting global communication infrastructure construction.The article also proposes improvement suggestions for existing issues and points out future research directions.
基金supported by the Chinese Meridian Project(CMP) and the National Natural Science Foundation of China(grant Nos.42230203,42374220,and 12173086)。
文摘The Spectral Imaging Corona Graph(SICG) serves as the optical observation equipment of E-corona in the Chinese Meridian Project Phase II, which aims at monitoring the initial source of solar activities. For the purpose of indepth exploration and space weather forecast in the full chain of Sun–Earth space, SICG is designed to work at two wavelengths of 637.4 and 530.3 nm in the quasi-simultaneous observation mode. Thus, the photometric calibration is more challenging to guarantee accurate scientific data of SICG. Two solar photometers are specially developed to match the observing wavelengths and make the photoelectronic conversion traceable. Correspondingly, the calibration process selects the solar disk center as the brightness reference, which compensates for the photometric losses along the atmospheric transmission path. This study derives the calibration coefficients from the two photometers for the E-coronal brightness processing in real time. By modeling aerosol absorption and scattering and comparing with continuous flat-field observation, the photometric calibration of SICG is evaluated with deviations of 2.1% and 2.3% at 637.4 nm and 530.3 nm, respectively. Based on this, the evolution speed of a multitemperature coronal loop was analyzed, facilitating further research into the physical mechanisms of coronal mass ejections.
文摘1 Summary Mathematical modeling has become a cornerstone in understanding the complex dynamics of infectious diseases and chronic health conditions.With the advent of more refined computational techniques,researchers are now able to incorporate intricate features such as delays,stochastic effects,fractional dynamics,variable-order systems,and uncertainty into epidemic models.These advancements not only improve predictive accuracy but also enable deeper insights into disease transmission,control,and policy-making.Tashfeen et al.
基金supported by National Natural Science Foundation of China(grant Nos.42274227,41904168,U1931122)National Key R&D Program of China No.2021 YFA0718600,and the Chinese Meridian Project(CMP).
文摘The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective lens.Due to the random accumulation of dust on the lens surfaces,it is challenging to monitor this type of stray light and no application can be used for its real-time monitor in the past.In this study,we provide a system and method to overcome this issue,and these have been applied to the Spectral Imaging CoronaGraph(SICG)of the Chinese Meridian Project.The method is based on the relation between the sizes of dust particles and its stray light level at the imaging plane established in the laboratory and the relation between the real size of dust particles and the occupancies on the imaging plane.To monitor the stray light levels accounted for by dusts,one needs only an image of the objective lens that can be provided by the auxiliary imaging system that specially comes with SICG.Our tests show that the errors of the method are less or about 2%,giving a strong confidence in its accuracy.It provides a handy tool to monitor the dust level of the objective lens of SICG and has significantly improved the efficiency of the pipeline of stray light control.
基金supported by National Natural Science Foundation of China under Grants 42374201,42274206,42374187Natural Science Foundation of Jiangxi Province under grants 20243BCE51,20243BCE51151 and 20232BAB213078.
文摘Exohiss are broadband,structureless whistler-mode waves outside the plasmapause.In our work,using the data sets detected by the EMFISIS suite aboard Van Allen Probe A,from 1st January 2013 to 30th June 2017,the exohiss waves are categorized among two types based on the direction of Poynting flux:unidirectional exohiss,and bidirectional exohiss waves.It seems that most exohiss waves are bidirectional,which are mainly distributed on the dayside.Compared to the hiss waves within the plasmasphere,the amplitude of bidirectional exohiss waves on the prenoon side increase very little with the enhancement of geomagnetic activity.Through the analysis of suprathermal electron flux associated with geomagnetic activity,this suggests that the waves may undergo very strong Landau damping during intense geomagnetic activity.On the other hand,the unidirectional exohiss waves are mainly distributed on the afternoon side,and the largest unidirectional exohiss waves are observed during the highest levels of substorm activity.
基金supported by the National Key R&D Program of China (Grant No. 2022YFF0503700)the special funds of Hubei Luojia Laboratory (220100011)+1 种基金Chao Xiong is supported by the ISSI-BJ project, “the electromagnetic data validation and scientific application research based on CSES satellite”ISSI/ISSI-BJ project “Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction”。
文摘In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.
基金supported by the National Natural Science Foundation of China (No. 42225405 and No. 42350710200)。
文摘The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cosmic ray albedo neutron decay(CRAND),radial diffusion, and local acceleration have been considered principal sources of electrons, whereas protons are predominantly from CRAND and solar protons. In this article, lightning-induced neutrons from Earth's upper atmosphere are suggested as a possible source of protons and electrons in the inner radiation belt. These terrestrial neutrons can contribute to the inner belt population by undergoing nuclear decay. Several approaches are proposed and discussed to evaluate the potential contribution of lightning-induced neutrons to the inner belt, including magnitude estimation, Monte Carlo simulations, and in situ observations. This article discusses some avenues of further study to determine the contribution of lightning-induced neutrons to the inner radiation belt.
基金supported by the National Key R&D Program of China No.2022YFF0503800the Strategic Priority Research Program of the Chinese Academy of Sciences(grant Nos.XDA17040507 and XDB0560000)+1 种基金NSFC grant 11933009the Yunnan Province Scientist Workshop of Solar Physics,the Yunnan Key Laboratory of Solar Physics and Space Science(202205AG070009)。
文摘A 50 mm balloon-borne white-light coronagraph(BBWLC)to observe white-light solar corona over the altitude range from 1.08 R_(⊙)to 1.50 R_(⊙)has recently been indigenously developed by Yunnan Observatories in collaboration with Shandong University(in Weihai)and Changchun Institute of Optics,Fine Mechanics and Physics,which will significantly improve the ability of China to detect and measure the inner corona.On 2022 October 4,its first scientific flight took place at the Dachaidan area in Qinghai province of China.We briefly describe the BBWLC mission including its optical design,mechanical structure,pointing system,the first flight and results associated with the data processing approach.Preliminary analysis of the data shows that BBWLC imaged the K-corona with three streamer structures on the west limb of the Sun.To further confirm the coronal signals obtained by BBWLC,comparisons were made with observations of the K-coronagraph of the High Altitude Observatory and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory.We conclude that BBWLC eventually observed the white-light corona in its first scientific flight.
基金supported by the National Natural Science Foundation of China (NSFC,grant No.12425301)the Strategic Priority Research Program of the Chinese Academy of Sciences (grant No.XDB0560000)+6 种基金the National Key R&D Program of China No.2022YFF0503800support from the National Natural Science Foundation of China (NSFC,grant No.12203030)supported by the C1 grant TRACEspace of Internal Funds KU Leuven and a Senior Research Project (G088021N) of the FWO Vlaanderensupport from the Flemish Government under the long-term structural Methusalem funding program,project SOUL:Stellar evolution in full glory,grant METH/24/012 at KU Leuvensubsidized by the Belgian Federal Science Policy Office through the contract B2/223/P1/CLOSE-UPfunding under the Horizon Europe program of the European Union under grant agreement (No.101131534)support by an FWO (Fonds voor Wetenschappelijk Onderzoek-Vlaanderen)postdoctoral fellowship (1273221N)
文摘Recent observations have demonstrated the capability of mapping the solar coronal magnetic field using the technique of coronal seismology based on the ubiquitous propagating Alfvénic/kink waves through imaging spectroscopy.We established a magnetohydrodynamic model of a gravitationally stratified open magnetic flux tube,exciting kink waves propagating upwards along the tube.Forward modeling was performed to synthesize the Fe XIII 1074.7 and 1079.8 nm spectral line profiles,which were then used to determine the wave phase speed,plasma density,and magnetic field with seismology method.A comparison between the seismologically inferred results and the corresponding input values verifies the reliability of the seismology method.In addition,we also identified some factors that could lead to errors during magnetic field measurements.Our results may serve as a valuable reference for current and future coronal magnetic field measurements based on observations of propagating kink waves.
基金supported by the National Natural Science Foundation of China(Grants 42325404,42120104003,42204164,42474219 and U22A2006)the Chinese Meridian Project,the International Partnership Program of Chinese Academy of Sciences(Grant 183311KYSB20200003)+7 种基金Shandong Provincial Natural Science Foundation(Grants ZR2022QD077,ZR2022MD034)the Stable-Support Scientific Project of China Research Institute of Radiowave Propagation(Grant A132312191)the foundation of the National Key Laboratory of Electromagnetic Environment(Grant 6142403180204)the Chongqing Natural Science Foundation(Grants cstc2021ycjh-bgzxm0072,CSTB2023NSCQ-LZX0082)National Program on Key Basic Research Project(Grant 2022173-SD-1)The work in Norway is supported by the Research Council of Norway Grant 326039Work at UCLA has been supported by NSF grant AGS-2055192This research was supported by the International Space Science Institute(ISSI)in Bern and Beijing,through ISSI International Team project#511(Multi-Scale Magnetosphere-Ionosphere-Thermosphere Interaction).
文摘This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches,in relation to the interplanetary magnetic field(IMF)and ionospheric convection geometry.A total of 11,946 patch events were identified by Defense Meteorological Satellite Program(DMSP)F16 during the years 2011 to 2022.A temperature ratio of ion/electron temperature(T_(i)/T_(e))<0.68 is recommended to define a hot patch in the Southern Hemisphere,otherwise it is defined as a cold patch.The cold and hot patches have different dependencies on IMF clock angle,while their dependencies on IMF cone angle are similar.Both cold and hot patches appear most often on the duskside,and the distribution of cold patches gradually decreases from the dayside to the nightside,while hot patches have a higher occurrence rate near 14 and 21 magnetic local time(MLT).Moreover,we compared the key plasma characteristics of polar cap cold and hot patches in the Southern and Northern Hemispheres.The intensity of the duskside upward field-aligned current of patches in the Southern Hemisphere(SH)is stronger than that in the Northern Hemisphere(SH),which may be due to the discrepancy in conductivities between the two hemispheres,caused by the tilted dipole.In both hemispheres,the downward soft-electron energy flux of the dawnside patches is significantly greater than that of the duskside patches.
