Solar wind charge exchange(SWCX)is the process of solar wind high-valence ions exchanging charges with neutral components and generating soft X-rays.Recently,detecting the SWCX emission from the magnetosphere is propo...Solar wind charge exchange(SWCX)is the process of solar wind high-valence ions exchanging charges with neutral components and generating soft X-rays.Recently,detecting the SWCX emission from the magnetosphere is proposed as a new technique to study the magnetosphere using panoramic soft X-ray imaging.To better prepare for the data analysis of upcoming magnetospheric soft X-ray imaging missions,this paper compares the magnetospheric SWCX emission obtained by two methods in an XMM-Newton observation,during which the solar wind changed dramatically.The two methods differ in the data used to fit the diffuse X-ray background(DXB)parameters in spectral analysis.The method adding data from the ROSAT All-Sky Survey(RASS)is called the RASS method.The method using the quiet observation data is called the Quiet method,where quiet observations usually refer to observations made by the same satellite with the same target but under weaker solar wind conditions.Results show that the spectral compositions of magnetospheric SWCX emission obtained by the two methods are very similar,and the changes in intensity over time are highly consistent,although the intensity obtained by the RASS method is about 2.68±0.56 keV cm^(-2)s^(-1)sr^(-1)higher than that obtained by the Quiet method.Since the DXB intensity obtained by the RASS method is about 2.84±0.74 keV cm^(-2)s^(-1)sr^(-1)lower than that obtained by the Quiet method,and the linear correlation coefficient between the difference of SWCX and DXB obtained by the two methods in diffe rent energy band is close to-1,the diffe rences in magnetospheric SWCX can be fully attributed to the diffe rences in the fitted DXB.The difference between the two methods is most significant when the energy is less than 0.7 keV,which is also the main energy band of SWCX emission.In addition,the difference between the two methods is not related to the SWCX intensity and,to some extent,to solar wind conditions,because SWCX intensity typically va ries with the solar wind.In summary,both methods are robust and reliable,and should be considered based on the best available options.展开更多
The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)Soft X-ray Imager(SXI)will shine a spotlight on magnetopause dynamics during magnetic reconnection.We simulate an event with a southward interplanetary magne...The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)Soft X-ray Imager(SXI)will shine a spotlight on magnetopause dynamics during magnetic reconnection.We simulate an event with a southward interplanetary magnetic field turning and produce SXI count maps with a 5-minute integration time.By making assumptions about the magnetopause shape,we find the magnetopause standoff distance from the count maps and compare it with the one obtained directly from the magnetohydrodynamic(MHD)simulation.The root mean square deviations between the reconstructed and MHD standoff distances do not exceed 0.2 RE(Earth radius)and the maximal difference equals 0.24 RE during the 25-minute interval around the southward turning.展开更多
In-depth studies of solar flares emissions and energy releases include analyses of polarization data. Polarization gives clear information about mechanisms and processes leading to electron acceleration and photon pro...In-depth studies of solar flares emissions and energy releases include analyses of polarization data. Polarization gives clear information about mechanisms and processes leading to electron acceleration and photon production. Despite of many past attempts, the key energy range of hard X-rays was only rarely explored and results were inconclusive. To large extend it was due to greater instrumental complications. Currently several novel polarimeters are either to be employed or under constructions for both balloon and satellite based observations. The novel hard X-ray polarimeter POLAR is an instrument developed by a collaboration between Switzerland, China and Poland. It is primarily designed for high accuracy polarization measurements from the prompt photon emissions of the gamma-ray bursts. The satellite orientation and instrument pointing direction make it also capable for precise measurements of polarization in solar flares. The instrument should fly in near future onboard of the Chinese Space Station TG2.展开更多
Astronomical imaging technologies are basic tools for the exploration of the universe,providing basic data for the research of astronomy and space physics.The Soft X-ray Imager(SXI)carried by the Solar wind Magnetosph...Astronomical imaging technologies are basic tools for the exploration of the universe,providing basic data for the research of astronomy and space physics.The Soft X-ray Imager(SXI)carried by the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)aims to capture two-dimensional(2-D)images of the Earth’s magnetosheath by using soft X-ray imaging.However,the observed 2-D images are affected by many noise factors,destroying the contained information,which is not conducive to the subsequent reconstruction of the three-dimensional(3-D)structure of the magnetopause.The analysis of SXI-simulated observation images shows that such damage cannot be evaluated with traditional restoration models.This makes it difficult to establish the mapping relationship between SXIsimulated observation images and target images by using mathematical models.We propose an image restoration algorithm for SXIsimulated observation images that can recover large-scale structure information on the magnetosphere.The idea is to train a patch estimator by selecting noise–clean patch pairs with the same distribution through the Classification–Expectation Maximization algorithm to achieve the restoration estimation of the SXI-simulated observation image,whose mapping relationship with the target image is established by the patch estimator.The Classification–Expectation Maximization algorithm is used to select multiple patch clusters with the same distribution and then train different patch estimators so as to improve the accuracy of the estimator.Experimental results showed that our image restoration algorithm is superior to other classical image restoration algorithms in the SXI-simulated observation image restoration task,according to the peak signal-to-noise ratio and structural similarity.The restoration results of SXI-simulated observation images are used in the tangent fitting approach and the computed tomography approach toward magnetospheric reconstruction techniques,significantly improving the reconstruction results.Hence,the proposed technology may be feasible for processing SXI-simulated observation images.展开更多
A multichannel low-noise electronic prototype system was designed for a pixelated CdZnTe detector. This system is the result of preliminary work on a solar hard X-ray imager, which is one of the three payloads for fut...A multichannel low-noise electronic prototype system was designed for a pixelated CdZnTe detector. This system is the result of preliminary work on a solar hard X-ray imager, which is one of the three payloads for future solar observations satellite-Advanced Space-based Solar Observatory(ASO-S). A new charge-sensitive amplifier application-specific integrated circuit, VATA450.3, with an on-chip analog-to-digital converter, is used to read out 8×8 anode pixel signals. Two CdZnTe detectors with a thickness of 2 mm and 5 mm were tested. The 2-mm-thick detector achieved energy resolution better than 5%(fullwidth at half-maximum, FWHM) at 59.5 keV, and the 5-mm-thick detector had better resolution than 1.2%(FWHM) at 662 keV. The design and test results of the prototype system are discussed in this paper.展开更多
A spaceborne hard X-ray spectrometer, composed of an array of 99 scintillation detectors and associated readout electronics, has been developed for the hard X-ray imager(HXI). The HXI is one of the three payloads onbo...A spaceborne hard X-ray spectrometer, composed of an array of 99 scintillation detectors and associated readout electronics, has been developed for the hard X-ray imager(HXI). The HXI is one of the three payloads onboard the advanced space-based solar observatory(ASO-S), which is scheduled to be launched in early 2022 as the first Chinese solar satellite. LaBr3 scintillators and photomultiplier tubes with a super bialkali cathode are used to achieve an energy resolution better than 20% at 30 keV.Further, a new multi-channel charge-sensitive readout application-specific integrated circuit guarantees high-frequency data acquisition with low power consumption. This paper presents a detailed design of the spectrometer for the engineering model of the HXI and discusses its noise and linearity performance.展开更多
We present the preliminary results of VLF signal perturbations produced due to solar flare. The data were recorded by the Stanford VLF AWESOME receiver located at National University of Ma-laysia, Selangor. Two new lo...We present the preliminary results of VLF signal perturbations produced due to solar flare. The data were recorded by the Stanford VLF AWESOME receiver located at National University of Ma-laysia, Selangor. Two new long distance (>1000 km) VLF paths, JJI-UKM (2700 km) and NWC-UKM (3300 km) were analyzed simultaneously. Data from the GOES satellite were used to determine the onset time and type of each of these flares. Results indicated that all five solar flare events with an X-ray peak flux above 10-5 W/m2 (M-class) were recorded, 37.5% for X-ray flux greater than 10-6 W/m2 (C-class), while the weakest X-ray flux recorded was 2.6 × 10-7 W/m2 (B-class) with 0.24% probing potentiality. We found a strong positive correlation (0.84) between solar flare radiation intensity and the values of amplitude and phase perturbations for both paths. The values of amplitude and phase perturbations time-correlated with solar flare, varied from 0.2 to 5 dB and 0.15 to 20 degree respectively. These findings are in complete agreement with previous works and demonstrate that the data obtained by the UKM AWESOME observation station will provide addi-tional contribution to the study of ELF/VLF waves phenomena in the ionosphere/magnetosphere, especially at low latitudes region.展开更多
The present study investigates the changes in TEC(total electron content)and ionospheric scintillation index(S4)inferred from the GNSS data recorded at the SCINDA station of Abidjan(Latitude=5.34°N,Longitude=3.90...The present study investigates the changes in TEC(total electron content)and ionospheric scintillation index(S4)inferred from the GNSS data recorded at the SCINDA station of Abidjan(Latitude=5.34°N,Longitude=3.90°W)during and after a solar flare.In the course of 2014,a year of high solar activity,three(3)cases of extreme(X1.66)and moderate(M6.23 and M2.13)solar flares recorded in the months of September and December effects on the ionosphere have been studied using the X ray fluxes,the magnetic parameters(Vx,Bz,Dst),the ionospheric scintillation index S4 and TEC and its ROT(time rate of change).The ROT exhibits a prominent peak between ten(10)and twelve(12)minutes after the occurrence of the maximum peak of the time rate of change of the X-ray flux emitted during the flare.The ROT maximum value occurs simultaneously with an enhancement of the S4 index.Deferred perturbations of the solar flare on the TEC in the SCINDA station of Abidjan occur within 42 to 54 hours after an M-class solar flare and within 46 to 58 hours following an X-Class solar flare.The magnetic storms resulted from these flares show an increment of 20%on VTEC observed when compared to the average VTEC(<VTECquiet>)computed from the most five(5)quietest days of the selected months.展开更多
Using the method recently developed by Can et al. (2001a, 2002), We investigate the time variation of the lower energy cutoff (Ec) of nonthermal electrons for three BATSE/CGRO hard X-ray events. The result shows tha...Using the method recently developed by Can et al. (2001a, 2002), We investigate the time variation of the lower energy cutoff (Ec) of nonthermal electrons for three BATSE/CGRO hard X-ray events. The result shows that Ec changes with time, from smaller before the peak flux, to larger at the peak, and then back to smaller after the peak. Such a variation of Ec, being a preliminary conclusion for the first time, should be checked in the future by using data with a higher energy resolution.展开更多
A quantitative method to determine the lower energy cutoff (Ec) of power-law electron beams is established. We apply this method to the 54 hard X-ray events observed with BATSE/Compton Gamma Ray Observatory (CGRO). Th...A quantitative method to determine the lower energy cutoff (Ec) of power-law electron beams is established. We apply this method to the 54 hard X-ray events observed with BATSE/Compton Gamma Ray Observatory (CGRO). The results show that about 75% of the observed broken double power-law spectra of hard X-rays can be explained by a lower energy cutoff in the power-law electron beams. The values of Ec, varying among the flares, are all greater than the usually accepted 20 keV! On average, E~ is about 69 keV. So high a lower energy cutoff of nonthermal electrons implies that nonthermal electrons might not be as important in powering solar flares as was previously thought. Further significance of this finding is discussed.展开更多
In this paper we have reviewed our achievements in soft X-ray and extreme ultraviolet (EUV) optics. Up to now, the research system of soft X-ray and EUV optics has been established, including light sources, detectors,...In this paper we have reviewed our achievements in soft X-ray and extreme ultraviolet (EUV) optics. Up to now, the research system of soft X-ray and EUV optics has been established, including light sources, detectors, calibrations, optical testing and machining of super smooth mirrors, and fabrications of multilayer film mirrors. Based on our achievements, we have developed two types of solar space telescopes for the soft X-ray and EUV space solar observations. One is an EUV multilayer normal incident telescope array including 4 different operation wavelength telescopes. The operation wavelengths of the EUV telescope are 13.0, 17.1, 19.5 and 30.4 nm. The other is a complex space solar telescope, which is composed of an EUV multilayer normal incident telescope and a soft X-ray grazing incident telescope. The EUV multilayer normal incident telescope stands in the central part of the soft X-ray grazing incident telescope. The normal incident telescope and the grazing incident telescope have a common detector. The different operation wavelengths can be changed by rotating a filter wheel.展开更多
We briefly introduce our recent work on the spectral evolution of energetic protons, the beam property of accelerated electrons, the gamma-ray flare classification, the temporal features of the annihilation line, the ...We briefly introduce our recent work on the spectral evolution of energetic protons, the beam property of accelerated electrons, the gamma-ray flare classification, the temporal features of the annihilation line, the hard X-ray delayed events, the hydrodynamic process, and the continuum emission in solar flares.展开更多
White-light (WL) flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the im...White-light (WL) flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatio-temporal correlation between the WL emission and the hard X-ray (HXR) radiation, presumably suggesting that energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares (〉M5) observed simultaneously by the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), and the Reuven Ramaty High Energy Solar Spectroscopic lmager (RHESS1). Among these events, WL emission was detected by SDO/HMI in 13 flares, associated with HXR emission. To quantitatively describe the strength of WL emission, equivalent area (EA) is defined as the integrated contrast enhancement over the entire flaring area. Our results show that the EA is inversely proportional to the HXR power-law index, indicating that stronger WL emission tends to be associated with a larger population of high energy electrons. However, no obvious correlation is found between WL emission and flux of non-thermal electrons at 50 keV. For the other group of 13 flares without detectable WL emission, the HXR spectra are softer (larger power-law index) than those flares with WL emission, especially for the X-class flares in this group.展开更多
Breakthroughs in energy storage and conversion devices depend heavily on the exploration of low-cost and high-performance materials.Carbon-supported electrocatalysts with dimensional varieties have recently attracted ...Breakthroughs in energy storage and conversion devices depend heavily on the exploration of low-cost and high-performance materials.Carbon-supported electrocatalysts with dimensional varieties have recently attracted significant attention due to their strong structural flexibility and easy accessibility.Nevertheless,understanding the connection between their electronic,structural properties,and catalytic performance must remain a top priority.Synchrotron radiation(SR)X-ray absorption spectroscopy(XAS)techniques,including hard XAS and soft XAS,are recognized as efficient and comprehensive platforms for probing the surface,interface,and bulk electronic structure of elements of interest in the materials community.In the past decade,the flourishing development of materials science and advanced characterization technologies have led to a deeper understanding at different temporal,longitudinal,and spatial scales.In this review,we briefly describe the concept of XAS techniques and summarize their recent progress in addressing scientific questions on carbon-supported electrocatalysts through the development of advanced instruments and experimental methods.We then discuss the remaining challenges and potential research directions in nextgeneration materials frontiers,and suggest challenges and perspectives for shedding light on the structure–activity relationship.展开更多
The Neupert effect suggests a flare model in which the nonthermal emissions are produced by energetic electrons which heat lower corona and chromosphere to produce the thermal emissions. Based on this concept, we inve...The Neupert effect suggests a flare model in which the nonthermal emissions are produced by energetic electrons which heat lower corona and chromosphere to produce the thermal emissions. Based on this concept, we investigate the Neupert effect to test the correlation between the hard X-ray spectral index and the time rate of the UV flare area at 1600 or 171 . Using the T RACE and RHESSI observations, we explore these quantities for two solar flares, one on March 14, 2002 and the other on November 1, 2003. The negative dependence between the spectral index and the time rate of the UV flare area is found, especially during the hard X-ray sub-peaks. This finding indicates that the electron-beam-driven heating plays a prominent role in the UV emission of these two flares.展开更多
During the upward period of solar cycle 23, the imaging riometer at Zhongshan, Antarctica (geomag. lat. 74.5°S) was used to study the solar proton events and the X-ray solar flares which are associated with the a...During the upward period of solar cycle 23, the imaging riometer at Zhongshan, Antarctica (geomag. lat. 74.5°S) was used to study the solar proton events and the X-ray solar flares which are associated with the absorption events. In our study, the relationship between the absorption intensity and X-ray flux is found in a power form which is consistent with the theoretical result. The imaging riometer absorption data at Ny-Alesund, Svalbard reconfirm the above relationship. We also argue that only M-class flares can generate a significant daytime absorption.展开更多
Growing observations reveal that soft gamma-ray repeaters and anomalous x-ray pulsars are magnetars. Their magnetic fields may achieve 10^14 - 10^15G. We explore the origin of the superstrong magnetic field by conside...Growing observations reveal that soft gamma-ray repeaters and anomalous x-ray pulsars are magnetars. Their magnetic fields may achieve 10^14 - 10^15G. We explore the origin of the superstrong magnetic field by considering the magnetization of the ^3P2 superfluid neutrons inside neutron stars (NSs). By solving the Tolman-Oppenheimer-Volkov equations together with the equation of state adopted by Elgaroy it et al. [Phys. Rev. Lett. 77 (1996) 1428] in the calculation of the neutron pairing gap, we specifically calculate the NS internal structure, the permissible region for ^3P2 superfluid neutrons inside the NS, and the total magnetic moment contributed by the orderly arranged neutron vortexes. The result shows that the induced magnetic field may cover a wide range, which is consistent with the magnetic field predicted by the standard magnetic dipole radiation for pulsar spindown.展开更多
基金supported by NNSFC grants 42322408,42188101 and 42074202the Strategic Pioneer Program on Space Science,CAS Grant nos.XDA15350201+3 种基金in part by the Research Fund from the Chinese Academy of Sciencesthe Specialized Research Fund for State Key Laboratories of China.supported by the Young Elite Scientists Sponsorship Program(CAST-Y202045)supported by Royal Society grant DHFR1211068。
文摘Solar wind charge exchange(SWCX)is the process of solar wind high-valence ions exchanging charges with neutral components and generating soft X-rays.Recently,detecting the SWCX emission from the magnetosphere is proposed as a new technique to study the magnetosphere using panoramic soft X-ray imaging.To better prepare for the data analysis of upcoming magnetospheric soft X-ray imaging missions,this paper compares the magnetospheric SWCX emission obtained by two methods in an XMM-Newton observation,during which the solar wind changed dramatically.The two methods differ in the data used to fit the diffuse X-ray background(DXB)parameters in spectral analysis.The method adding data from the ROSAT All-Sky Survey(RASS)is called the RASS method.The method using the quiet observation data is called the Quiet method,where quiet observations usually refer to observations made by the same satellite with the same target but under weaker solar wind conditions.Results show that the spectral compositions of magnetospheric SWCX emission obtained by the two methods are very similar,and the changes in intensity over time are highly consistent,although the intensity obtained by the RASS method is about 2.68±0.56 keV cm^(-2)s^(-1)sr^(-1)higher than that obtained by the Quiet method.Since the DXB intensity obtained by the RASS method is about 2.84±0.74 keV cm^(-2)s^(-1)sr^(-1)lower than that obtained by the Quiet method,and the linear correlation coefficient between the difference of SWCX and DXB obtained by the two methods in diffe rent energy band is close to-1,the diffe rences in magnetospheric SWCX can be fully attributed to the diffe rences in the fitted DXB.The difference between the two methods is most significant when the energy is less than 0.7 keV,which is also the main energy band of SWCX emission.In addition,the difference between the two methods is not related to the SWCX intensity and,to some extent,to solar wind conditions,because SWCX intensity typically va ries with the solar wind.In summary,both methods are robust and reliable,and should be considered based on the best available options.
基金support from the UK Space Agency under Grant Number ST/T002964/1partly supported by the International Space Science Institute(ISSI)in Bern,through ISSI International Team Project Number 523(“Imaging the Invisible:Unveiling the Global Structure of Earth’s Dynamic Magnetosphere”)。
文摘The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)Soft X-ray Imager(SXI)will shine a spotlight on magnetopause dynamics during magnetic reconnection.We simulate an event with a southward interplanetary magnetic field turning and produce SXI count maps with a 5-minute integration time.By making assumptions about the magnetopause shape,we find the magnetopause standoff distance from the count maps and compare it with the one obtained directly from the magnetohydrodynamic(MHD)simulation.The root mean square deviations between the reconstructed and MHD standoff distances do not exceed 0.2 RE(Earth radius)and the maximal difference equals 0.24 RE during the 25-minute interval around the southward turning.
文摘In-depth studies of solar flares emissions and energy releases include analyses of polarization data. Polarization gives clear information about mechanisms and processes leading to electron acceleration and photon production. Despite of many past attempts, the key energy range of hard X-rays was only rarely explored and results were inconclusive. To large extend it was due to greater instrumental complications. Currently several novel polarimeters are either to be employed or under constructions for both balloon and satellite based observations. The novel hard X-ray polarimeter POLAR is an instrument developed by a collaboration between Switzerland, China and Poland. It is primarily designed for high accuracy polarization measurements from the prompt photon emissions of the gamma-ray bursts. The satellite orientation and instrument pointing direction make it also capable for precise measurements of polarization in solar flares. The instrument should fly in near future onboard of the Chinese Space Station TG2.
基金supported by the National Natural Science Foundation of China(Grant Nos.42322408,42188101,41974211,and 42074202)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDJ-SSW-JSC028)+1 种基金the Strategic Priority Program on Space Science,Chinese Academy of Sciences(Grant Nos.XDA15052500,XDA15350201,and XDA15014800)supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y202045)。
文摘Astronomical imaging technologies are basic tools for the exploration of the universe,providing basic data for the research of astronomy and space physics.The Soft X-ray Imager(SXI)carried by the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)aims to capture two-dimensional(2-D)images of the Earth’s magnetosheath by using soft X-ray imaging.However,the observed 2-D images are affected by many noise factors,destroying the contained information,which is not conducive to the subsequent reconstruction of the three-dimensional(3-D)structure of the magnetopause.The analysis of SXI-simulated observation images shows that such damage cannot be evaluated with traditional restoration models.This makes it difficult to establish the mapping relationship between SXIsimulated observation images and target images by using mathematical models.We propose an image restoration algorithm for SXIsimulated observation images that can recover large-scale structure information on the magnetosphere.The idea is to train a patch estimator by selecting noise–clean patch pairs with the same distribution through the Classification–Expectation Maximization algorithm to achieve the restoration estimation of the SXI-simulated observation image,whose mapping relationship with the target image is established by the patch estimator.The Classification–Expectation Maximization algorithm is used to select multiple patch clusters with the same distribution and then train different patch estimators so as to improve the accuracy of the estimator.Experimental results showed that our image restoration algorithm is superior to other classical image restoration algorithms in the SXI-simulated observation image restoration task,according to the peak signal-to-noise ratio and structural similarity.The restoration results of SXI-simulated observation images are used in the tangent fitting approach and the computed tomography approach toward magnetospheric reconstruction techniques,significantly improving the reconstruction results.Hence,the proposed technology may be feasible for processing SXI-simulated observation images.
基金supported by the National Natural Science Funds of China(Nos.11622327,11273070,11773087,U1631116)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2014275)the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences(No.XDA15010200)
文摘A multichannel low-noise electronic prototype system was designed for a pixelated CdZnTe detector. This system is the result of preliminary work on a solar hard X-ray imager, which is one of the three payloads for future solar observations satellite-Advanced Space-based Solar Observatory(ASO-S). A new charge-sensitive amplifier application-specific integrated circuit, VATA450.3, with an on-chip analog-to-digital converter, is used to read out 8×8 anode pixel signals. Two CdZnTe detectors with a thickness of 2 mm and 5 mm were tested. The 2-mm-thick detector achieved energy resolution better than 5%(fullwidth at half-maximum, FWHM) at 59.5 keV, and the 5-mm-thick detector had better resolution than 1.2%(FWHM) at 662 keV. The design and test results of the prototype system are discussed in this paper.
基金supported by the Strategic Priority Program Stage Ⅱ on Space Science of Chinese Academy of Sciences(No.XDA15320104)the National Natural Science Foundation of China(Nos.11703097,11427803,11820101002,11622327,11773087,U1631116,and 11803093)
文摘A spaceborne hard X-ray spectrometer, composed of an array of 99 scintillation detectors and associated readout electronics, has been developed for the hard X-ray imager(HXI). The HXI is one of the three payloads onboard the advanced space-based solar observatory(ASO-S), which is scheduled to be launched in early 2022 as the first Chinese solar satellite. LaBr3 scintillators and photomultiplier tubes with a super bialkali cathode are used to achieve an energy resolution better than 20% at 30 keV.Further, a new multi-channel charge-sensitive readout application-specific integrated circuit guarantees high-frequency data acquisition with low power consumption. This paper presents a detailed design of the spectrometer for the engineering model of the HXI and discusses its noise and linearity performance.
文摘We present the preliminary results of VLF signal perturbations produced due to solar flare. The data were recorded by the Stanford VLF AWESOME receiver located at National University of Ma-laysia, Selangor. Two new long distance (>1000 km) VLF paths, JJI-UKM (2700 km) and NWC-UKM (3300 km) were analyzed simultaneously. Data from the GOES satellite were used to determine the onset time and type of each of these flares. Results indicated that all five solar flare events with an X-ray peak flux above 10-5 W/m2 (M-class) were recorded, 37.5% for X-ray flux greater than 10-6 W/m2 (C-class), while the weakest X-ray flux recorded was 2.6 × 10-7 W/m2 (B-class) with 0.24% probing potentiality. We found a strong positive correlation (0.84) between solar flare radiation intensity and the values of amplitude and phase perturbations for both paths. The values of amplitude and phase perturbations time-correlated with solar flare, varied from 0.2 to 5 dB and 0.15 to 20 degree respectively. These findings are in complete agreement with previous works and demonstrate that the data obtained by the UKM AWESOME observation station will provide addi-tional contribution to the study of ELF/VLF waves phenomena in the ionosphere/magnetosphere, especially at low latitudes region.
文摘The present study investigates the changes in TEC(total electron content)and ionospheric scintillation index(S4)inferred from the GNSS data recorded at the SCINDA station of Abidjan(Latitude=5.34°N,Longitude=3.90°W)during and after a solar flare.In the course of 2014,a year of high solar activity,three(3)cases of extreme(X1.66)and moderate(M6.23 and M2.13)solar flares recorded in the months of September and December effects on the ionosphere have been studied using the X ray fluxes,the magnetic parameters(Vx,Bz,Dst),the ionospheric scintillation index S4 and TEC and its ROT(time rate of change).The ROT exhibits a prominent peak between ten(10)and twelve(12)minutes after the occurrence of the maximum peak of the time rate of change of the X-ray flux emitted during the flare.The ROT maximum value occurs simultaneously with an enhancement of the S4 index.Deferred perturbations of the solar flare on the TEC in the SCINDA station of Abidjan occur within 42 to 54 hours after an M-class solar flare and within 46 to 58 hours following an X-Class solar flare.The magnetic storms resulted from these flares show an increment of 20%on VTEC observed when compared to the average VTEC(<VTECquiet>)computed from the most five(5)quietest days of the selected months.
文摘Using the method recently developed by Can et al. (2001a, 2002), We investigate the time variation of the lower energy cutoff (Ec) of nonthermal electrons for three BATSE/CGRO hard X-ray events. The result shows that Ec changes with time, from smaller before the peak flux, to larger at the peak, and then back to smaller after the peak. Such a variation of Ec, being a preliminary conclusion for the first time, should be checked in the future by using data with a higher energy resolution.
基金National Natural Science Foundation of China via grants 19525308,9883002,49990451 grant G2000078402 from the Ministry of Science and Tec hnology of China.
文摘A quantitative method to determine the lower energy cutoff (Ec) of power-law electron beams is established. We apply this method to the 54 hard X-ray events observed with BATSE/Compton Gamma Ray Observatory (CGRO). The results show that about 75% of the observed broken double power-law spectra of hard X-rays can be explained by a lower energy cutoff in the power-law electron beams. The values of Ec, varying among the flares, are all greater than the usually accepted 20 keV! On average, E~ is about 69 keV. So high a lower energy cutoff of nonthermal electrons implies that nonthermal electrons might not be as important in powering solar flares as was previously thought. Further significance of this finding is discussed.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40774098 and 10878004)
文摘In this paper we have reviewed our achievements in soft X-ray and extreme ultraviolet (EUV) optics. Up to now, the research system of soft X-ray and EUV optics has been established, including light sources, detectors, calibrations, optical testing and machining of super smooth mirrors, and fabrications of multilayer film mirrors. Based on our achievements, we have developed two types of solar space telescopes for the soft X-ray and EUV space solar observations. One is an EUV multilayer normal incident telescope array including 4 different operation wavelength telescopes. The operation wavelengths of the EUV telescope are 13.0, 17.1, 19.5 and 30.4 nm. The other is a complex space solar telescope, which is composed of an EUV multilayer normal incident telescope and a soft X-ray grazing incident telescope. The EUV multilayer normal incident telescope stands in the central part of the soft X-ray grazing incident telescope. The normal incident telescope and the grazing incident telescope have a common detector. The different operation wavelengths can be changed by rotating a filter wheel.
基金the National Natural Science Foundation of China (Grant Nos. 19525308, 9883002, 49990451, 10173027) Ministry of Science and Technology of China(G2000078402).
文摘We briefly introduce our recent work on the spectral evolution of energetic protons, the beam property of accelerated electrons, the gamma-ray flare classification, the temporal features of the annihilation line, the hard X-ray delayed events, the hydrodynamic process, and the continuum emission in solar flares.
基金supported by NSF grants AGS-1539791, AGS-1250374, AGS-1408703 and AGS-1348513
文摘White-light (WL) flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatio-temporal correlation between the WL emission and the hard X-ray (HXR) radiation, presumably suggesting that energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares (〉M5) observed simultaneously by the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), and the Reuven Ramaty High Energy Solar Spectroscopic lmager (RHESS1). Among these events, WL emission was detected by SDO/HMI in 13 flares, associated with HXR emission. To quantitatively describe the strength of WL emission, equivalent area (EA) is defined as the integrated contrast enhancement over the entire flaring area. Our results show that the EA is inversely proportional to the HXR power-law index, indicating that stronger WL emission tends to be associated with a larger population of high energy electrons. However, no obvious correlation is found between WL emission and flux of non-thermal electrons at 50 keV. For the other group of 13 flares without detectable WL emission, the HXR spectra are softer (larger power-law index) than those flares with WL emission, especially for the X-class flares in this group.
基金supported in part by the National Key R&D Program of China(Nos.2020YFA0405800,2022YFA1504104,and 2022YFA1605400)the National Natural Science Foundation of China(Nos.12225508,12322515,U1932201,U2032113,and 22075264)+5 种基金the Youth Innovation Promotion Association of CAS(No.2022457)the Institute of Energy,Hefei Comprehensive National Science Center,University Synergy Innovation Program of Anhui Province(No.GXXT-2020-002)and the CAS Iterdisciplinary Innovation Team.We thank the Shanghai Synchrotron Radiation Facility(BL14W1,BL14B1,and SSRF)the Beijing Synchrotron Radiation Facility(1W1B,4B7A,and BSRF)the Hefei Synchrotron Radiation Facility(Infrared Spectroscopy and Microspectroscopy,MCD-A and MCD-B Soochow Beamline for Energy Materials at NSRL)and the USTC Center for Micro and Nanoscale Research and Fabrication for helps in characterizations.
文摘Breakthroughs in energy storage and conversion devices depend heavily on the exploration of low-cost and high-performance materials.Carbon-supported electrocatalysts with dimensional varieties have recently attracted significant attention due to their strong structural flexibility and easy accessibility.Nevertheless,understanding the connection between their electronic,structural properties,and catalytic performance must remain a top priority.Synchrotron radiation(SR)X-ray absorption spectroscopy(XAS)techniques,including hard XAS and soft XAS,are recognized as efficient and comprehensive platforms for probing the surface,interface,and bulk electronic structure of elements of interest in the materials community.In the past decade,the flourishing development of materials science and advanced characterization technologies have led to a deeper understanding at different temporal,longitudinal,and spatial scales.In this review,we briefly describe the concept of XAS techniques and summarize their recent progress in addressing scientific questions on carbon-supported electrocatalysts through the development of advanced instruments and experimental methods.We then discuss the remaining challenges and potential research directions in nextgeneration materials frontiers,and suggest challenges and perspectives for shedding light on the structure–activity relationship.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10603014, 10843005, and 10833007)the National Basic Research Program of China (Grant No. 2006CB06302)the CAS project (KJCX2-YW-T04)
文摘The Neupert effect suggests a flare model in which the nonthermal emissions are produced by energetic electrons which heat lower corona and chromosphere to produce the thermal emissions. Based on this concept, we investigate the Neupert effect to test the correlation between the hard X-ray spectral index and the time rate of the UV flare area at 1600 or 171 . Using the T RACE and RHESSI observations, we explore these quantities for two solar flares, one on March 14, 2002 and the other on November 1, 2003. The negative dependence between the spectral index and the time rate of the UV flare area is found, especially during the hard X-ray sub-peaks. This finding indicates that the electron-beam-driven heating plays a prominent role in the UV emission of these two flares.
基金the National Natural Science Foundation ofChina (Grant No. 49639160), the major project of Chinese Academy of Sciences (Grant No. KJ951-1-305) and the Oceanic Youth Foundation of State Oceanic Administration (Grant No. 98605).
文摘During the upward period of solar cycle 23, the imaging riometer at Zhongshan, Antarctica (geomag. lat. 74.5°S) was used to study the solar proton events and the X-ray solar flares which are associated with the absorption events. In our study, the relationship between the absorption intensity and X-ray flux is found in a power form which is consistent with the theoretical result. The imaging riometer absorption data at Ny-Alesund, Svalbard reconfirm the above relationship. We also argue that only M-class flares can generate a significant daytime absorption.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10173005, 10273006 and 19935030, and the Doctoral Programme of the Ministry of Education of China.
文摘Growing observations reveal that soft gamma-ray repeaters and anomalous x-ray pulsars are magnetars. Their magnetic fields may achieve 10^14 - 10^15G. We explore the origin of the superstrong magnetic field by considering the magnetization of the ^3P2 superfluid neutrons inside neutron stars (NSs). By solving the Tolman-Oppenheimer-Volkov equations together with the equation of state adopted by Elgaroy it et al. [Phys. Rev. Lett. 77 (1996) 1428] in the calculation of the neutron pairing gap, we specifically calculate the NS internal structure, the permissible region for ^3P2 superfluid neutrons inside the NS, and the total magnetic moment contributed by the orderly arranged neutron vortexes. The result shows that the induced magnetic field may cover a wide range, which is consistent with the magnetic field predicted by the standard magnetic dipole radiation for pulsar spindown.