This study analyzes total electron content(TEC)variations during two solar eclipse events that occurred on October 25,2022,and October 14,2023.The solar eclipse of October 25,2022,was a partial solar eclipse,while the...This study analyzes total electron content(TEC)variations during two solar eclipse events that occurred on October 25,2022,and October 14,2023.The solar eclipse of October 25,2022,was a partial solar eclipse,while the eclipse of October 14,2023,was an annular solar eclipse.For this study,the data of eight International GNSS Service(IGS)stations from different eclipse coverage zones are used to analyze TEC variations.It is found that the stations located in the maximum eclipse cover zone exhibited notable decreases in TEC values.The minimum variation of about 11.76%in TEC values is observed at the station situating in about 20 percent eclipse cover zone,while it varies from 22%to 38%at the stations falling in about 60 percent eclipse cover zone.The highest variation in TEC values of about 44%is found at the stations in about 80 percent eclipse cover zone.The time of occurrence of maximum depletion in TEC values at each station is in line with their longitudinal sequence.Atmospheric gravity waves(AGWs)are also observed by performing wavelet analysis on TEC data.The global TEC maps visualize and confirm observed TEC variations,providing spatial and temporal insights into the ionospheric response.This analysis highlights the influence of station location and eclipse coverage on the magnitude and spatial distribution of TEC variations.展开更多
A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in...A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in Science on May 23 as a rare case:it turns out to be eclipsed by a companion,very likely a helium star,with a mass similar to the Sun and in an orbit smaller than the solar radius.展开更多
During the total solar eclipse of 2013 November 3, a fiber-based spectrometer captured the flash spectrum within the wavelength range of 5162–5325Å, with the field-of-view positioned approximately 0.04 R⊙above ...During the total solar eclipse of 2013 November 3, a fiber-based spectrometer captured the flash spectrum within the wavelength range of 5162–5325Å, with the field-of-view positioned approximately 0.04 R⊙above the east limb, near the second-contact point. This placement near the innermost corona, together with the nearby Baily's beads, enabled the detection of emission lines from the photosphere, lower chromosphere, and corona in the same spectral frame. The higher field-of-view made the coronal line Fe XIV 5303Åmore visible, while the reduced intensity of photospheric and lower chromospheric light, caused by terrestrial scattering, also influenced the observed spectrum. Meanwhile, we selected 18 flash emission lines to measure the ratio of the relative line height of the flash emission line to the relative line depth of the corresponding solar absorption line. This ratio serves as a diagnostic of the source function, minimizing opacity effects. Comparison of disk and flash spectra shows that this ratio increases for spectral lines at greater formation heights, being strongest for chromospheric lines(particularly Fe II), moderate for photospheric low-FIP lines, and weakest for photospheric neutral lines. This trend suggests a rising source function with formation height, potentially linked to increasing electron temperatures or influenced by factors observed in flash spectra near active regions as reported in earlier studies.展开更多
This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI an...This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI and Ti80 titanium alloys.Slow strain rate tensile(SSRT)tests were performed to evaluate SCC susceptibility.The SCC susceptibility index(I_(SSRT))was calculated,and the fracture morphologies were investigated to clarify the stress corrosion mechanisms.The experimental results show that the ISSRT of Ti6411 titanium alloy with a lamellar micro structure(LM)is the highest under a strain rate of 1×10^(-6)s^(-1),and the corresponding fracture mode shows a quasi-cleavage fracture with low ductility.TC4ELI alloy with an equiaxed microstructure exhibits excellent SCC resistance.However,the SCC behavior of the Ti80 alloy with a bimodal microstructure is relatively sensitive to high strain rates,and the Ti52 tube with a typical Widmanst?tten microstructure is sensitive to low strain rates.The stress corrosion mechanism can be attributed to the cyclic process of passive film rupture,anodic dissolution,and hydrogen-induced cracking due to a multifactor comprehensive interaction corresponding to specific microstructures,strain rates,and corrosive media.The LM of the Ti6411 plate allowed easy chloride penetration into the bare metal,thereby reducing the protection of the film and resulting in continuous anodic dissolution and hydrogen accumulation at the crack tip.The coupled effect of the internal hydrogen pressure and external tensile stress can easily cause crack propagation and failure under service conditions.展开更多
基金the Global GNSS-TEC data processing has been supported by JSPS KAKENHI Grant Number 16H06286。
文摘This study analyzes total electron content(TEC)variations during two solar eclipse events that occurred on October 25,2022,and October 14,2023.The solar eclipse of October 25,2022,was a partial solar eclipse,while the eclipse of October 14,2023,was an annular solar eclipse.For this study,the data of eight International GNSS Service(IGS)stations from different eclipse coverage zones are used to analyze TEC variations.It is found that the stations located in the maximum eclipse cover zone exhibited notable decreases in TEC values.The minimum variation of about 11.76%in TEC values is observed at the station situating in about 20 percent eclipse cover zone,while it varies from 22%to 38%at the stations falling in about 60 percent eclipse cover zone.The highest variation in TEC values of about 44%is found at the stations in about 80 percent eclipse cover zone.The time of occurrence of maximum depletion in TEC values at each station is in line with their longitudinal sequence.Atmospheric gravity waves(AGWs)are also observed by performing wavelet analysis on TEC data.The global TEC maps visualize and confirm observed TEC variations,providing spatial and temporal insights into the ionospheric response.This analysis highlights the influence of station location and eclipse coverage on the magnitude and spatial distribution of TEC variations.
文摘A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in Science on May 23 as a rare case:it turns out to be eclipsed by a companion,very likely a helium star,with a mass similar to the Sun and in an orbit smaller than the solar radius.
基金supported by the National Natural Science Foundation of China(NSFC)under grant Nos.12473054 and 12127901the Strategic Priority Research Program of the Chinese Academy of Sciences under grant No.XDB0560000+1 种基金Yunnan Key Laboratory of Solar Physics and Space Science under No.202205AG070009Yunnan Fundamental Research Projects under No.202105AC160085.
文摘During the total solar eclipse of 2013 November 3, a fiber-based spectrometer captured the flash spectrum within the wavelength range of 5162–5325Å, with the field-of-view positioned approximately 0.04 R⊙above the east limb, near the second-contact point. This placement near the innermost corona, together with the nearby Baily's beads, enabled the detection of emission lines from the photosphere, lower chromosphere, and corona in the same spectral frame. The higher field-of-view made the coronal line Fe XIV 5303Åmore visible, while the reduced intensity of photospheric and lower chromospheric light, caused by terrestrial scattering, also influenced the observed spectrum. Meanwhile, we selected 18 flash emission lines to measure the ratio of the relative line height of the flash emission line to the relative line depth of the corresponding solar absorption line. This ratio serves as a diagnostic of the source function, minimizing opacity effects. Comparison of disk and flash spectra shows that this ratio increases for spectral lines at greater formation heights, being strongest for chromospheric lines(particularly Fe II), moderate for photospheric low-FIP lines, and weakest for photospheric neutral lines. This trend suggests a rising source function with formation height, potentially linked to increasing electron temperatures or influenced by factors observed in flash spectra near active regions as reported in earlier studies.
基金the financial support from the National Key R&D Program of China(No.2022YFB3705605)。
文摘This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI and Ti80 titanium alloys.Slow strain rate tensile(SSRT)tests were performed to evaluate SCC susceptibility.The SCC susceptibility index(I_(SSRT))was calculated,and the fracture morphologies were investigated to clarify the stress corrosion mechanisms.The experimental results show that the ISSRT of Ti6411 titanium alloy with a lamellar micro structure(LM)is the highest under a strain rate of 1×10^(-6)s^(-1),and the corresponding fracture mode shows a quasi-cleavage fracture with low ductility.TC4ELI alloy with an equiaxed microstructure exhibits excellent SCC resistance.However,the SCC behavior of the Ti80 alloy with a bimodal microstructure is relatively sensitive to high strain rates,and the Ti52 tube with a typical Widmanst?tten microstructure is sensitive to low strain rates.The stress corrosion mechanism can be attributed to the cyclic process of passive film rupture,anodic dissolution,and hydrogen-induced cracking due to a multifactor comprehensive interaction corresponding to specific microstructures,strain rates,and corrosive media.The LM of the Ti6411 plate allowed easy chloride penetration into the bare metal,thereby reducing the protection of the film and resulting in continuous anodic dissolution and hydrogen accumulation at the crack tip.The coupled effect of the internal hydrogen pressure and external tensile stress can easily cause crack propagation and failure under service conditions.
