Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.008
Yang Chen , Deng Li-cai , Yang Fan , He Fei , Wang Kun , Li Rui-yue , Lan Tian , Ren An-bing , Liu Nian , Zhang Chun-guang , Chen Xiao-dian , Liu Qi-li
Starting in the early 2000s, China's astronomical community undertook a strategic survey for optical observing sites in the broader Qinghai-Tibet Plateau region. In 2016, site-specific monitoring was conducted based on the preliminary work for the 13th Five-Year Plan's major scientific engineering projects, including the plan of a 10 meter Large Optical/Infrared Telescope (LOT). Although not selected as a candidate site, this spurred the site survey in the Lenghu area. Since 2018, continuous site-specific monitoring of Lenghu has been carried out, yielding continuous data on site quality parameters under seeing limited conditions. Data shows that the site quality of the Saishiteng Mountain in Lenghu is excellent and meets the needs for new large optical equipments by domestic research institutions. Additionally, the geographical location of the Qinghai-Tibet Plateau fills a significant gap in the geographical longitude distribution of international quality sites, presenting major opportunities for time-domain scientific research and international cooperation. This paper summarizes the experiences and main scientific results of the Lenghu site selection and construction, and introduces the optical telescope projects that have been operational and signed at Lenghu.
{"title":"Astronomical Observing Site Selection on the Tibetan Plateau—Lenghu: A Site Capable of Hosting the Future Development of Optical Astronomy in China","authors":"Yang Chen , Deng Li-cai , Yang Fan , He Fei , Wang Kun , Li Rui-yue , Lan Tian , Ren An-bing , Liu Nian , Zhang Chun-guang , Chen Xiao-dian , Liu Qi-li","doi":"10.1016/j.chinastron.2024.11.008","DOIUrl":"10.1016/j.chinastron.2024.11.008","url":null,"abstract":"<div><div>Starting in the early 2000s, China's astronomical community undertook a strategic survey for optical observing sites in the broader Qinghai-Tibet Plateau region. In 2016, site-specific monitoring was conducted based on the preliminary work for the 13th Five-Year Plan's major scientific engineering projects, <strong>including the plan of a 10 meter Large Optical/Infrared Telescope (LOT)</strong>. Although not selected as a candidate site, this spurred the site survey in the Lenghu area. Since 2018, continuous site-specific monitoring of Lenghu has been carried out, yielding continuous data on site quality parameters under seeing limited conditions. Data shows that the site quality of the Saishiteng Mountain in Lenghu is excellent and meets the needs for new large optical equipments by domestic research institutions. Additionally, the geographical location of the Qinghai-Tibet Plateau fills a significant gap in the geographical longitude distribution of international quality sites, presenting major opportunities for time-domain scientific research and international cooperation. This paper summarizes the experiences and main scientific results of the Lenghu site selection and construction, and introduces the optical telescope projects that have been operational and signed at Lenghu.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 613-634"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The frequency stability and uncertainty of the optical clock have reached a magnitude of , making it a promising candidate for the next generation of time and frequency standards, and it may be used to redefine the international unit “second”. The time scale serves as a benchmark for accurately and continuously marking the passage of time, being the foundation of high-precision time generation. The production of a time scale relies on the continuous and stable operation of atomic clocks; however, optical clocks, as laboratory prototype devices, generally cannot operate continuously, thus involving optical clocks in time scale calculation presents a challenging issue. The proposed application of the Vondrak-Cepek combined filtering algorithm for joint time scale calculations with an optical clock and hydrogen masers aims to address the challenges posed by the intermittent operation of an optical clock. Initially, the ALGOS algorithm is used on the time difference data of the hydrogen masers to calculate and obtain a continuous and stable hydrogen maser clock time scale. Subsequently, the Vondrak-Cepek combined filtering algorithm is used to integrate the hydrogen maser time scale with the optical clock data to acquire a combined time scale that involves optical clocks in the calculation. Finally, the experimental results prove that the Vondrak-Cepek combined filtering algorithm effectively improves the performance of the combined time scale of optical clocks and hydrogen masers, with the time deviation of this time scale reaching the sub-nanosecond magnitude when compared with Coordinated Universal Time (UTC).
{"title":"Combination of an Optical Clock and Hydrogen Masers for Accurate Time Scale Calculation","authors":"Zhao Shu-hong , Dong Shao-wu , Bai Shan-shan , Qu Li-li , Zhang Ji-hai , Zhang Yu","doi":"10.1016/j.chinastron.2024.11.009","DOIUrl":"10.1016/j.chinastron.2024.11.009","url":null,"abstract":"<div><div>The frequency stability and uncertainty of the optical clock have reached a magnitude of <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>18</mn></mrow></msup></math></span>, making it a promising candidate for the next generation of time and frequency standards, and it may be used to redefine the international unit “second”. The time scale serves as a benchmark for accurately and continuously marking the passage of time, being the foundation of high-precision time generation. The production of a time scale relies on the continuous and stable operation of atomic clocks; however, optical clocks, as laboratory prototype devices, generally cannot operate continuously, thus involving optical clocks in time scale calculation presents a challenging issue. The proposed application of the Vondrak-Cepek combined filtering algorithm for joint time scale calculations with an optical clock and hydrogen masers aims to address the challenges posed by the intermittent operation of an optical clock. Initially, the ALGOS algorithm is used on the time difference data of the hydrogen masers to calculate and obtain a continuous and stable hydrogen maser clock time scale. Subsequently, the Vondrak-Cepek combined filtering algorithm is used to integrate the hydrogen maser time scale with the optical clock data to acquire a combined time scale that involves optical clocks in the calculation. Finally, the experimental results prove that the Vondrak-Cepek combined filtering algorithm effectively improves the performance of the combined time scale of optical clocks and hydrogen masers, with the time deviation of this time scale reaching the sub-nanosecond magnitude when compared with Coordinated Universal Time (UTC).</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 763-780"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.010
Zhou Zhi-chao , Chen Lin-jie , Yan Yi-hua , Wang Wei
The MUSER, a new generation of solar-dedicated radio imaging spectroscopic telescope, has achieved high-time, high-angular, and high-frequency resolution imaging of the Sun within the 0.4–15 GHz ultra-broadband frequency range. The radio brightness temperature is a critical parameter in describing solar physical processes. It plays a significant role in studying various radio radiation mechanisms, the solar magnetic field, and the acceleration of non-thermal particles during solar bursts, making brightness temperature calibration essential for radioheliograph images. This paper introduces a method suitable for calibrating the intensity of radioheliograph images. Given that solar radio images contain structural information about the solar disk, the radio radius and intensity of the quiet solar disk can be obtained by fitting Bessel function of the first kind with the visibilities of short baselines from the radioheliograph. Subsequently, the Rayleigh-Jeans law and the daily solar radio flux are used to calculate the calibration factor for the daily image, thereby achieving image intensity calibration of the radioheliograph. Applying this method to actual observation data from MUSER, including scenarios such as the quiet Sun and solar radio bursts, shows that the error of the daily calibration factor is within 10% of its value, and the obtained brightness temperature of the quiet Sun strongly correlates with results from other studies. These results indicate the method's feasibility and effectiveness.
{"title":"Intensity Calibration for the Mingantu Spectral Radioheliograph Images","authors":"Zhou Zhi-chao , Chen Lin-jie , Yan Yi-hua , Wang Wei","doi":"10.1016/j.chinastron.2024.11.010","DOIUrl":"10.1016/j.chinastron.2024.11.010","url":null,"abstract":"<div><div>The MUSER, a new generation of solar-dedicated radio imaging spectroscopic telescope, has achieved high-time, high-angular, and high-frequency resolution imaging of the Sun within the 0.4–15 GHz ultra-broadband frequency range. The radio brightness temperature is a critical parameter in describing solar physical processes. It plays a significant role in studying various radio radiation mechanisms, the solar magnetic field, and the acceleration of non-thermal particles during solar bursts, making brightness temperature calibration essential for radioheliograph images. This paper introduces a method suitable for calibrating the intensity of radioheliograph images. Given that solar radio images contain structural information about the solar disk, the radio radius and intensity of the quiet solar disk can be obtained by fitting Bessel function of the first kind with the visibilities of short baselines from the radioheliograph. Subsequently, the Rayleigh-Jeans law and the daily solar radio flux are used to calculate the calibration factor <span><math><msub><mi>G</mi><mi>c</mi></msub></math></span> for the daily image, thereby achieving image intensity calibration of the radioheliograph. Applying this method to actual observation data from MUSER, including scenarios such as the quiet Sun and solar radio bursts, shows that the error of the daily calibration factor <span><math><msub><mi>G</mi><mi>c</mi></msub></math></span> is within 10% of its value, and the obtained brightness temperature of the quiet Sun strongly correlates with results from other studies. These results indicate the method's feasibility and effectiveness.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 797-809"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Advanced Space-based Solar Observatory (ASO-S), as one of the second series scientific satellites in the space science pilot project, was proposed by the Purple Mountain Observatory of Chinese Academy of Sciences. ASO-S aims to observe and investigate the two solar eruptive phenomena, i.e., solar flares and coronal mass ejections, and their relationships with magnetic field. Hard X-ray Imager (HXI) is one of the payloads aboard ASO-S. As an important part of HXI, the calorimeter is responsible for measuring solar hard X-rays in the energy range of 30–200 keV. Before the launch of ASO-S, a ground test system was necessary to verify the function and performance of the HXI calorimeter. There are 99 lanthanum bromide detectors in the HXI calorimeter, each controlled by 8 identical front-end electronic boards. In addition to testing the performance of each channel, the ground test system also needs to simulate the operation of the calorimeter under different solar activities in orbit, conducting a comprehensive test. Moreover, the ground test system needs to be stable enough to meet the long-term testing needs of the calorimeter in different tests, including standalone testing, environmental experiments, thermal vacuum and vibration tests. According to the test requirements, a ground test board and a software in the host computer were designed, combined with radioactive sources, a DC (Direct Current) power supply, and a high-voltage module to form a ground test system for the HXI calorimeter. It can simultaneously configure and manage 8 front-end electronic boards, efficiently complete command sending and data receiving, and meet the maximum data output bandwidth of 400 Mbps of the calorimeter. The ground test system can fully meet the requirement of automatic control, status monitoring, data acquisition and data analysis for the HXI calorimeter. Using this ground test system, all function and performance tests for the HXI calorimeter were completed with the acquisition of the noise, the dead time, the energy resolution and other performance data. The ground test system provides strong guarantee for the high performance operation of the HXI calorimeter in orbit.
{"title":"Design and Realization of the Calorimeter Test System for the Hard X-ray Imager","authors":"Chen Jiao-long , Zhang Yong-qiang , Zhang Yan , Guo Jian-hua","doi":"10.1016/j.chinastron.2024.11.002","DOIUrl":"10.1016/j.chinastron.2024.11.002","url":null,"abstract":"<div><div>The Advanced Space-based Solar Observatory (ASO-S), as one of the second series scientific satellites in the space science pilot project, was proposed by the Purple Mountain Observatory of Chinese Academy of Sciences. ASO-S aims to observe and investigate the two solar eruptive phenomena, i.e., solar flares and coronal mass ejections, and their relationships with magnetic field. Hard X-ray Imager (HXI) is one of the payloads aboard ASO-S. As an important part of HXI, the calorimeter is responsible for measuring solar hard X-rays in the energy range of 30–200 keV. Before the launch of ASO-S, a ground test system was necessary to verify the function and performance of the HXI calorimeter. There are 99 lanthanum bromide detectors in the HXI calorimeter, each controlled by 8 identical front-end electronic boards. In addition to testing the performance of each channel, the ground test system also needs to simulate the operation of the calorimeter under different solar activities in orbit, conducting a comprehensive test. Moreover, the ground test system needs to be stable enough to meet the long-term testing needs of the calorimeter in different tests, including standalone testing, environmental experiments, thermal vacuum and vibration tests. According to the test requirements, a ground test board and a software in the host computer were designed, combined with radioactive sources, a DC (Direct Current) power supply, and a high-voltage module to form a ground test system for the HXI calorimeter. It can simultaneously configure and manage 8 front-end electronic boards, efficiently complete command sending and data receiving, and meet the maximum data output bandwidth of 400 Mbps of the calorimeter. The ground test system can fully meet the requirement of automatic control, status monitoring, data acquisition and data analysis for the HXI calorimeter. Using this ground test system, all function and performance tests for the HXI calorimeter were completed with the acquisition of the noise, the dead time, the energy resolution and other performance data. The ground test system provides strong guarantee for the high performance operation of the HXI calorimeter in orbit.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 810-829"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.006
Ma Bin-yuan , Yang Zi-xu , Liao Jin-yuan , Qu Jin-lu
Through decades of observations and studies, the characteristics of black hole X-ray binaries (XRBs) have been gradually revealed. However, the structure of the accretion disk remains uncertain. In the power density spectrum of the BHXRB (Black Hole X-ray Binaries), there is a correlation between the break frequency and the quasi-periodic oscillation (W-K relation), and it can constrain the current model of accretion disk. The W-K relation in black hole XRBs is studied based on the observations of five black hole XRBs by Insight-HXMT (Hard X-ray Modulation Telescope). The result shows that the W-K relation is valid in all the three telescopes with different energy bands. Moreover, a correlation between the break frequency and the inner radius of the accretion disk is found for MAXI J1535-571, which is self-consistent with the model of a truncated accretion disk. If the observed power density spectra result from the propagation of fluctuation in mass accretion rate, it can be further inferred that the inner radius of the accretion disk is close to the innermost stable circular orbit, and the black hole might be a high-spin system.
{"title":"The W-K Relation in Black Hole X-ray Binaries from Insight-HXMT Observation","authors":"Ma Bin-yuan , Yang Zi-xu , Liao Jin-yuan , Qu Jin-lu","doi":"10.1016/j.chinastron.2024.11.006","DOIUrl":"10.1016/j.chinastron.2024.11.006","url":null,"abstract":"<div><div>Through decades of observations and studies, the characteristics of black hole X-ray binaries (XRBs) have been gradually revealed. However, the structure of the accretion disk remains uncertain. In the power density spectrum of the BHXRB (Black Hole X-ray Binaries), there is a correlation between the break frequency and the quasi-periodic oscillation (W-K relation), and it can constrain the current model of accretion disk. The W-K relation in black hole XRBs is studied based on the observations of five black hole XRBs by <em>Insight</em>-HXMT (Hard X-ray Modulation Telescope). The result shows that the W-K relation is valid in all the three telescopes with different energy bands. Moreover, a correlation between the break frequency and the inner radius of the accretion disk is found for MAXI J1535-571, which is self-consistent with the model of a truncated accretion disk. If the observed power density spectra result from the propagation of fluctuation in mass accretion rate, it can be further inferred that the inner radius of the accretion disk is close to the innermost stable circular orbit, and the black hole might be a high-spin system.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 705-723"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.005
Liu Mu-lin , Hou Xi-yun
Asteroid detection is now a hot spot of solar system exploration. The understanding of the evolution of asteroids has a great benefit on researches to the origin of the solar system. An important topic of the evolution research is the evolution of inner structures of asteroids, in other words, asteroids' evolution of shapes and structures under multiple mechanisms. A common method to simulate the dynamical evolution of asteroids is Discrete Element Method (DEM) under the assumption that asteroids are in rubble-pile structures. Some teams have developed several kinds of softwares for DEM simulations. The basics, realization, algorithms of our software “Multi-particle system simulation software based on DEM algorithm” are introduced in this article, and the software is verified using two body collision, sound wave propagation, inner stress of asteroid, and asteroid spin disruption setups.
{"title":"Discrete Element Method Simulation System for Asteroid","authors":"Liu Mu-lin , Hou Xi-yun","doi":"10.1016/j.chinastron.2024.11.005","DOIUrl":"10.1016/j.chinastron.2024.11.005","url":null,"abstract":"<div><div>Asteroid detection is now a hot spot of solar system exploration. The understanding of the evolution of asteroids has a great benefit on researches to the origin of the solar system. An important topic of the evolution research is the evolution of inner structures of asteroids, in other words, asteroids' evolution of shapes and structures under multiple mechanisms. A common method to simulate the dynamical evolution of asteroids is Discrete Element Method (DEM) under the assumption that asteroids are in rubble-pile structures. Some teams have developed several kinds of softwares for DEM simulations. The basics, realization, algorithms of our software “Multi-particle system simulation software based on DEM algorithm” are introduced in this article, and the software is verified using two body collision, sound wave propagation, inner stress of asteroid, and asteroid spin disruption setups.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 724-748"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.007
Tulpar Turgun , Yan Jing-ye , Wu Lin , Yang Yang , Lan Ai-lan , Wu Ji
Daocheng Solar Radio Telescope (DSRT) is an important part of the solar interplanetary exploration subsystem of the Chinese Meridian Project-Phase II. It operates in the 150450 MHz frequency band, providing high-time, high-angular resolution images of the solar radio burst. Aiming at the high precision pointing measurement of the DSRT antenna and the requirement of batch calibration of pointing errors, the antenna's 3-parameter encoder zero-point offset pointing error model is established by quaternion rotation transformation method according to the unique 3-axis mount system of the DSRT. Then, the drift scanning method based on radio source is proposed to obtain the radiation power pattern of the 16 antennas, and the pointing errors are accurately measured by determining the boresight according to the 2-dimensional power pattern. Finally, the least square method is used to fit the model parameters, and the encoder zero point is readjusted for each axis via antenna control software. Verification of the adjustment results confirmed the reliability and effectiveness of the pointing calibration method. After correction, the pointing accuracy of 16 antennas is within 0.5, which is significantly better than the pointing error of 3.5 before calibration, meeting the requirement that errors are less than 1/10 of the HBPW (half power beam width) at the highest operating frequency of the DSRT antenna.
{"title":"Batch Measurement and Calibration Method of DSRT Three-axis Low Frequency Antenna Pointing Error","authors":"Tulpar Turgun , Yan Jing-ye , Wu Lin , Yang Yang , Lan Ai-lan , Wu Ji","doi":"10.1016/j.chinastron.2024.11.007","DOIUrl":"10.1016/j.chinastron.2024.11.007","url":null,"abstract":"<div><div>Daocheng Solar Radio Telescope (DSRT) is an important part of the solar interplanetary exploration subsystem of the Chinese Meridian Project-Phase II. It operates in the 150<span><math><mo>−</mo></math></span>450 MHz frequency band, providing high-time, high-angular resolution images of the solar radio burst. Aiming at the high precision pointing measurement of the DSRT antenna and the requirement of batch calibration of pointing errors, the antenna's 3-parameter encoder zero-point offset pointing error model is established by quaternion rotation transformation method according to the unique 3-axis mount system of the DSRT. Then, the drift scanning method based on radio source is proposed to obtain the radiation power pattern of the 16 antennas, and the pointing errors are accurately measured by determining the boresight according to the 2-dimensional power pattern. Finally, the least square method is used to fit the model parameters, and the encoder zero point is readjusted for each axis via antenna control software. Verification of the adjustment results confirmed the reliability and effectiveness of the pointing calibration method. After correction, the pointing accuracy of 16 antennas is within 0.5<span><math><msup><mrow></mrow><mo>∘</mo></msup></math></span>, which is significantly better than the pointing error of 3.5<span><math><msup><mrow></mrow><mo>∘</mo></msup></math></span> before calibration, meeting the requirement that errors are less than 1/10 of the HBPW (half power beam width) at the highest operating frequency of the DSRT antenna.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 781-796"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.003
Chai Li-hui , Guo Meng-dan , Tang Xiao-zhun
Using the observations by the Analyzer of Space Plasmas and Energetic Atoms on Venus (ASPERA-4) onboard Venus Express, Previous studies found a large-scale plasma vortice of solar wind hydrogen ions () and Venus ionospheric oxygen ions () in the magnetotail of Venus. The vortex is counterclockwise when viewed from the tail towards the planet. We conducted a statistical analysis of the ASPERA-4 moment data calibrated by Fedorov to investigate the plasma characteristics in Venusian magnetotail. The statistical results showed that there are large-scale vortices of the solar wind and Venus ionospheric in both the Venus-Solar-Orbital (VSO) and Venus-Solar-Electrical (VSE) coordinate systems, but they are clockwise. Considering that neither counterclockwise nor clockwise plasma vortices can generate a magnetic field consistent with the observed magnetic structure in the Venusian magnetotail, and no complete plasma vortex is observed in the Mars magnetotail with a magnetic structure similar to that of Venusian magnetotail, concluded that there may not be large-scale plasma vortices in the Venusian magnetotail, and that more satellite observations are needed in the future to investigate the plasma characteristics on Venus.
{"title":"Large-scale Plasma Vortex in the Magnetotail of Venus","authors":"Chai Li-hui , Guo Meng-dan , Tang Xiao-zhun","doi":"10.1016/j.chinastron.2024.11.003","DOIUrl":"10.1016/j.chinastron.2024.11.003","url":null,"abstract":"<div><div>Using the observations by the Analyzer of Space Plasmas and Energetic Atoms on Venus (ASPERA-4) onboard Venus Express, Previous studies found a large-scale plasma vortice of solar wind hydrogen ions (<span><math><msup><mi>H</mi><mo>+</mo></msup></math></span>) and Venus ionospheric oxygen ions (<span><math><msup><mi>O</mi><mo>+</mo></msup></math></span>) in the magnetotail of Venus. The vortex is counterclockwise when viewed from the tail towards the planet. We conducted a statistical analysis of the ASPERA-4 moment data calibrated by Fedorov to investigate the plasma characteristics in Venusian magnetotail. The statistical results showed that there are large-scale vortices of the solar wind <span><math><msup><mi>H</mi><mo>+</mo></msup></math></span> and Venus ionospheric <span><math><msup><mi>O</mi><mo>+</mo></msup></math></span> in both the Venus-Solar-Orbital (VSO) and Venus-Solar-Electrical (VSE) coordinate systems, but they are clockwise. Considering that neither counterclockwise nor clockwise plasma vortices can generate a magnetic field consistent with the observed magnetic structure in the Venusian magnetotail, and no complete plasma vortex is observed in the Mars magnetotail with a magnetic structure similar to that of Venusian magnetotail, concluded that there may not be large-scale plasma vortices in the Venusian magnetotail, and that more satellite observations are needed in the future to investigate the plasma characteristics on Venus.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 749-762"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.004
Cai Yi-fu , He Xin-chen , Ma Xiao-han
In the era of precision cosmology, multi-messenger, high-resolution as well as small-scale cosmological observations have provided profound insights into the early universe, while also presenting new challenges to cosmological perturbation theory based on linear approximation and perturbative expansions. In recent years, the search for primordial gravitational waves and primordial black holes has generated significant research interest in the non-linear and non-perturbative processes in the early universe on small scales. This review paper summarizes the progress in understanding the generation of primordial black holes and gravitational waves at cosmological small scales. Specifically, we focus on the application of the resonance effect depicted by Mathieu equation to study small-scale power spectrum amplification and the induction of observable primordial gravitational waves. Furthermore, we attempt to explore the influence of non-Gaussian tails on primordial black hole formation. Our findings indicate that the resonance effect of the Mathieu equation provides an effective approach to describe non-perturbative and non-linear processes on small scales in the early universe, leading to a better understanding of the mechanisms behind primordial black hole formation and gravitational wave generation. Additionally, the non-perturbative non-Gaussianity may have a significant impact on the formation of primordial black holes.
{"title":"Nonperturbative Phenomenons of the Very Early Universe: Resonances in Primordial Fluctuations and Non-Gaussian Tails","authors":"Cai Yi-fu , He Xin-chen , Ma Xiao-han","doi":"10.1016/j.chinastron.2024.11.004","DOIUrl":"10.1016/j.chinastron.2024.11.004","url":null,"abstract":"<div><div>In the era of precision cosmology, multi-messenger, high-resolution as well as small-scale cosmological observations have provided profound insights into the early universe, while also presenting new challenges to cosmological perturbation theory based on linear approximation and perturbative expansions. In recent years, the search for primordial gravitational waves and primordial black holes has generated significant research interest in the non-linear and non-perturbative processes in the early universe on small scales. This review paper summarizes the progress in understanding the generation of primordial black holes and gravitational waves at cosmological small scales. Specifically, we focus on the application of the resonance effect depicted by Mathieu equation to study small-scale power spectrum amplification and the induction of observable primordial gravitational waves. Furthermore, we attempt to explore the influence of non-Gaussian tails on primordial black hole formation. Our findings indicate that the resonance effect of the Mathieu equation provides an effective approach to describe non-perturbative and non-linear processes on small scales in the early universe, leading to a better understanding of the mechanisms behind primordial black hole formation and gravitational wave generation. Additionally, the non-perturbative non-Gaussianity may have a significant impact on the formation of primordial black holes.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 635-682"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.chinastron.2024.11.001
Cao Jie , Xu Ting-ting , Deng Yu-he , Li Guang-ping , Gao Xian-jun , Yang Ming-cun , Liu Zhi-jing , Zhou Wei-hong
With the development of artificial intelligence technology, the research of galaxy morphology classification using deep learning methods has made great progress, but there are still shortcomings in classification accuracy, automation, and spatial characteristics representation of galaxies. The Vision Transformer model (ViT) has good robustness in galaxy morphology classification, but has limitations in handling multi-scale images. In this paper, we propose to introduce the Feature Pyramid Networks (FPN) into the ViT model to classify galaxies. The results show that the average accuracy, precision, recall, and F1-score of the FPN-ViT model are above 95%, and the indexes are improved compared with the traditional ViT model. Meanwhile, we add different levels of Gaussian noise and pretzel noise to the original galaxy images to verify that the FPN-ViT model can obtain better classification performance for low signal-to-noise ratio data. In addition, to evaluate the model comprehensively, the t-distributed Stochastic Neighbor Embedding (t-SNE) algorithm is used to visualize and analyze the classification results, which can show the effect of FPN-ViT model on galaxy morphology classification more directly. The application of FPN network to the classification of galaxy morphology by ViT model is a new attempt, which is of great importance for the subsequent research.
{"title":"Classification of Galaxy Morphology Based on FPN-ViT Model","authors":"Cao Jie , Xu Ting-ting , Deng Yu-he , Li Guang-ping , Gao Xian-jun , Yang Ming-cun , Liu Zhi-jing , Zhou Wei-hong","doi":"10.1016/j.chinastron.2024.11.001","DOIUrl":"10.1016/j.chinastron.2024.11.001","url":null,"abstract":"<div><div>With the development of artificial intelligence technology, the research of galaxy morphology classification using deep learning methods has made great progress, but there are still shortcomings in classification accuracy, automation, and spatial characteristics representation of galaxies. The Vision Transformer model (ViT) has good robustness in galaxy morphology classification, but has limitations in handling multi-scale images. In this paper, we propose to introduce the Feature Pyramid Networks (FPN) into the ViT model to classify galaxies. The results show that the average accuracy, precision, recall, and F1-score of the FPN-ViT model are above 95%, and the indexes are improved compared with the traditional ViT model. Meanwhile, we add different levels of Gaussian noise and pretzel noise to the original galaxy images to verify that the FPN-ViT model can obtain better classification performance for low signal-to-noise ratio data. In addition, to evaluate the model comprehensively, the t-distributed Stochastic Neighbor Embedding (t-SNE) algorithm is used to visualize and analyze the classification results, which can show the effect of FPN-ViT model on galaxy morphology classification more directly. The application of FPN network to the classification of galaxy morphology by ViT model is a new attempt, which is of great importance for the subsequent research.</div></div>","PeriodicalId":35730,"journal":{"name":"Chinese Astronomy and Astrophysics","volume":"48 4","pages":"Pages 683-704"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143129318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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