This paper presents the analytical results of solar MgⅠb_(2)flash spectra,obtained by the prototype Fiber Arrayed Solar Optic Telescope in process of the 2013 Gabon total solar eclipse.The analysis reveals irregular ...This paper presents the analytical results of solar MgⅠb_(2)flash spectra,obtained by the prototype Fiber Arrayed Solar Optic Telescope in process of the 2013 Gabon total solar eclipse.The analysis reveals irregular distributions of the spectral line parameters like ratio of line source function to continuum oneβ,ratio of line emissivity to continuum emissivityζ,ratio of the continuum opacity to the line opacity r_(0),line center optical depthτ_(0)、,the line widthΔλ_(D),and the line-of-sight velocity v_(los),while the approximately spherical symmetry can be found in the maps of integrated line intensity and continuum intensity.These irregular distributions originate from those of line profile features like the maximum intensity,the line width and line center wavelength.It is also found from the recovered line center optical depthτ_(0) that in the middle chromosphere,the optical depth is not small due to nonignorable absorption and the long light path along the line-of-sight.Finally,we show that the excessive broadening of spectral lines can be due to co-existence of multiple radiative sources with different line-of-sight velocities unresolved in one detector pixel.展开更多
The in-flight calibration and performance of the Solar Disk Imager(SDI),which is a pivotal instrument of the LyαSolar Telescope onboard the Advanced Space-based Solar Observatory mission,suggested a much lower spatia...The in-flight calibration and performance of the Solar Disk Imager(SDI),which is a pivotal instrument of the LyαSolar Telescope onboard the Advanced Space-based Solar Observatory mission,suggested a much lower spatial resolution than expected.In this paper,we developed the SDI point-spread function(PSF)and Image Bivariate Optimization Algorithm(SPIBOA)to improve the quality of SDI images.The bivariate optimization method smartly combines deep learning with optical system modeling.Despite the lack of information about the real image taken by SDI and the optical system function,this algorithm effectively estimates the PSF of the SDI imaging system directly from a large sample of observational data.We use the estimated PSF to conduct deconvolution correction to observed SDI images,and the resulting images show that the spatial resolution after correction has increased by a factor of more than three with respect to the observed ones.Meanwhile,our method also significantly reduces the inherent noise in the observed SDI images.The SPIBOA has now been successfully integrated into the routine SDI data processing,providing important support for the scientific studies based on the data.The development and application of SPIBOA also paves new ways to identify astronomical telescope systems and enhance observational image quality.Some essential factors and precautions in applying the SPIBOA method are also discussed.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
Using the new soft X-ray data from the Macao Science Satellite-1,we studied a solar flare that occurred on 22 June 2023.We found that the centroids of the Ca(around 3.9 keV)and Fe(around 6.7 keV)line features exhibit ...Using the new soft X-ray data from the Macao Science Satellite-1,we studied a solar flare that occurred on 22 June 2023.We found that the centroids of the Ca(around 3.9 keV)and Fe(around 6.7 keV)line features exhibit a rapid shift toward higher energy channels during the flare's rising phase,followed by a gradual decrease during the decay phase.Through precise energy calibration,the centroids are determined with high accuracy.Temperature and velocity are then self-consistently derived by comparing the centroids with those calculated from the synthesized line features using the latest CHIANTI atomic database(ver.10.1).The calculated maximum velocity reaches up to 710±60 km s-1,which significantly exceeds the previously reported values.Our results suggest that the entire shift of soft X-ray lines may occur during the process of chromospheric evaporation.展开更多
The data of velocity and magnetic fields in the solar photosphere (5324 A) and thechromosphere (4861 A) clearly show the features of tangential discontinuity of velocity inthe chromosphere. The velocity fields in and ...The data of velocity and magnetic fields in the solar photosphere (5324 A) and thechromosphere (4861 A) clearly show the features of tangential discontinuity of velocity inthe chromosphere. The velocity fields in and near the solar active region named No. 88029by the Huairou Station have been analyzed in detail. A lot of magnetohydrodynamic discon-tinuous surfaces, especially the tangential discontinuities, are shown from the observations.The calculations of the thickness of discontinuous layer and the evoluiton time of instabilityagree with the observational results. The variations of the flow field will directly influencethe evolutions and changes of the active region as the magnetic field are coupled closelywith the plasma motion.展开更多
Low mass ratio contact binary systems are more likely to have unstable orbits and potentially merge.In addition,such systems exhibit characteristics such as starspots and high energy emissions(UV)suggestive of chromos...Low mass ratio contact binary systems are more likely to have unstable orbits and potentially merge.In addition,such systems exhibit characteristics such as starspots and high energy emissions(UV)suggestive of chromospheric and magnetic activity.Light curve modeling of ten contact binary systems is reported.All were found to be of extreme low mass ratio ranging from 0.122 to 0.24 and three were found to be potentially unstable and possible merger candidates.Filling of the infrared calcium absorption lines is a marker of increased chromospheric activity.We use the available Large Sky Area Multi-Object Fiber Spectroscopic Telescope spectra along with matched standard spectra(broadened for rotation)to measure the excess filling of the central core depression flux of the two main infrared calcium absorption linesλ8542 andλ8662.We find that all reported contact binaries have excess filling of the core flux in the infrared calcium lines.Three of the systems reported were also observed by the Galaxy Evolution Explorer mission and we find that all three have features of excess ultraviolet emissions further adding evidence for increased chromospheric activity in low mass ratio contact binaries.Analysis of both orbital stability and absorption line filling is dependent on the determination of geometric and absolute parameters from light curve modeling.Not an insignificant number of contact binary light curves exhibit the O’Connell effect,usually attributed to starspots.We discuss the inclusion of starspots in light curve solutions and how they influence the geometric and absolute parameters.展开更多
We study the nonlinear coupling of kinetic Alfvén waves with ion acoustic waves applicable to the Earth’s radiation belt and near-Sun streamer belt solar wind using dynamical equations in the form of modified Za...We study the nonlinear coupling of kinetic Alfvén waves with ion acoustic waves applicable to the Earth’s radiation belt and near-Sun streamer belt solar wind using dynamical equations in the form of modified Zakharov systems.Numerical simulations show the formation of magnetic field filamentary structures associated with density humps and dips which become turbulent at later times,redistributing the energy to higher wavenumbers.The magnetic power spectra exhibit an inertial range Kolmogorov-like spectral index value of-5/3 for k_(⊥)ρ_(i)<1 followed by a steeper dissipation range spectra with indices~-3 for the radiation belt case and~-4 for the nearSun streamer belt solar wind case,here k_(⊥)andρ_(i)represent the wavevector component perpendicular to the background magnetic field and the ion thermal gyroradius,respectively.Applying quasilinear theory in terms of the Fokker-Planck equation in the region of wavenumber turbulent spectra,we find the particle distribution function flattening in the superthermal tail population which is the signature of particle energization and plasma heating.展开更多
The characteristics of magnetohydrodynamic fast wave propagation in the solar stratified atmosphere are studied by the ray tracing method. The propagation behaviour of the wavefronts is described in detail. A magnetic...The characteristics of magnetohydrodynamic fast wave propagation in the solar stratified atmosphere are studied by the ray tracing method. The propagation behaviour of the wavefronts is described in detail. A magnetic field incorporating the characteristics field spreading expected in flux tubes is used, which represents the main feature of an active region. Partly ionization is considered beside the stratified solar atmosphere consisting chromosphere, transition region and corona. The study may explain the characteristics in observations of Moreton and extraultraviolet image telescope （EIT） waves. The wavefront incurred by the disturbance initialized at the base of the transition region propagates fast initially due to strong magnetic field, and it slows down when arriving beyond the region of flux-tube. Meanwhile, the wave propagates in the corona with a more consistent speed, as seen in the observation of EIT waves. The speeds and propagated characteristics in chromosphere and corona of the wavefronts are in agreement with those observed in H~ Moreton and EIT waves, respectively.展开更多
The Multi-wavelength Spectrometer is a medium-dispersion（R^130 000）grating spectrometer installed on the New Vacuum Solar Telescope at the Fuxian Solar Observatory,Yunnan Astronomical Observatory,Chinese Academy of ...The Multi-wavelength Spectrometer is a medium-dispersion（R^130 000）grating spectrometer installed on the New Vacuum Solar Telescope at the Fuxian Solar Observatory,Yunnan Astronomical Observatory,Chinese Academy of Sciences.It is designed to accurately observe the velocity and magnetic fields of the Sun.The present configuration of this spectrometer allows us to simultaneously observe three different solar spectral lines.This work is dedicated to showing the first observations carried out in both the Hαand Ca II 8542 A lines.We give a detailed description of the data reduction process,focusing on the retrieval of a flat field from the high-resolution spectral data.Two different methods are also performed and compared to eliminate the residual fringe in the reduced data.The real spectral resolution and instrumental profile are analyzed based on the final results,which indicate that this spectrometer presently satisfies the expected performance and it is ready for further scientific observations.展开更多
The emission sources of umbral flashes （UFs） are believed to be closely related to running umbral and penumbral waves, and are concluded to be associated with umbral dots in the solar photosphere. Accurate identific...The emission sources of umbral flashes （UFs） are believed to be closely related to running umbral and penumbral waves, and are concluded to be associated with umbral dots in the solar photosphere. Accurate identification of emission sources of UFs is crucial for investigating these physical phenomena and their inherent relationships. A relatively novel model of shape perception, namely phase congruency （PC）, uses phase information in the Fourier domain to identify the geometrical shape of the region of interest in different intensity levels, rather than intensity or gradient. Previous studies indicate that the model is suitable for identifying features with low contrast and low luminance. In the present paper, we applied the PC model to identify the emission sources of UFs and to locate their positions. For illustrating the high performance of our proposed method, two time sequences of Ca n H images derived from the Hinode/SOT on 2010 August 10 and 2013 August 20 were used. Furthermore, we also compared these results with the analysis results that are identified by the traditional/classical identification methods, including the gray-scale adjusted technique and the running difference technique. The result of our analysis demonstrates that our proposed method is more accurate and effective than the traditional identification methods when applied to identifying the emission sources of UFs and to locating their positions.展开更多
Suppressing the interference of atmospheric turbulence and obtaining observation data with a high spatial resolution are an issue to be solved urgently for ground observations. One way to solve this problem is to perf...Suppressing the interference of atmospheric turbulence and obtaining observation data with a high spatial resolution are an issue to be solved urgently for ground observations. One way to solve this problem is to perform a statistical reconstruction of short-exposure speckle images. Combining the rapidity of Shift-Add and the accuracy of speckle masking, this paper proposes a novel reconstruction algorithm-NASIR(Non-rigid Alignment based Solar Image Reconstruction). NASIR reconstructs the phase of the object image at each frequency by building a computational model between geometric distortion and intensity distribution and reconstructs the modulus of the object image on the aligned speckle images by speckle interferometry. We analyzed the performance of NASIR by using the correlation coefficient, power spectrum, and coefficient of variation of intensity profile in processing data obtained by the NVST(1 m New Vacuum Solar Telescope). The reconstruction experiments and analysis results show that the quality of images reconstructed by NASIR is close to speckle masking when the seeing is good, while NASIR has excellent robustness when the seeing condition becomes worse. Furthermore, NASIR reconstructs the entire field of view in parallel in one go, without phase recursion and block-by-block reconstruction, so its computation time is less than half that of speckle masking. Therefore, we consider NASIR is a robust and highquality fast reconstruction method that can serve as an effective tool for data filtering and quick look.展开更多
We present properties of intensity oscillations of a sunspot in the photo- sphere and chromosphere using G band and Ca u H filtergrams from Hinode. Intensity power maps as function of magnetic field strength and frequ...We present properties of intensity oscillations of a sunspot in the photo- sphere and chromosphere using G band and Ca u H filtergrams from Hinode. Intensity power maps as function of magnetic field strength and frequency reveal reduction of power in the G band with an increase in photospheric magnetic field strength at all frequencies. In Ca II H, however, stronger fields exhibit more power at high frequen- cies, particularly in the 4.5-8.0 mHz band. Power distributions in different locations of the active region show that the oscillations in Ca II H exhibit more power compared to that of the G band. We also relate the power in intensity oscillations with differ- ent components of the photospheric vector magnetic field using near simultaneous spectro-polarimetric observations of the sunspot from the Hinode spectropolarime- ter. The photospheric umbral power is strongly anti-correlated with the magnetic field strength and its line-of-sight component but there is a good correlation with the trans- verse component. A reversal of this trend is observed in the chromosphere except at low frequencies （V≤ 1.5 mHz）. The power in sunspot penumbrae is anti-correlated with the magnetic field parameters at all frequencies （1.0 ≤ v ≤ 8.0 mHz） in both the photosphere and chromosphere, except that the chromospheric power shows a strong correlation in the frequency range 3-3.5 mHz.展开更多
The Atmospheric Imaging Assembly(AIA)onboard the Solar Dynamics Observatory(SDO)provides full-disk solar images with high temporal cadence and spatial resolution over seven extreme ultraviolet(EUV)wave bands.However,a...The Atmospheric Imaging Assembly(AIA)onboard the Solar Dynamics Observatory(SDO)provides full-disk solar images with high temporal cadence and spatial resolution over seven extreme ultraviolet(EUV)wave bands.However,as violent solar flares happen,images captured in EUV wave bands may have saturation in active regions,resulting in signal loss.In this paper,we propose a deep learning model to restore the lost signal in saturated regions by referring to both unsaturated/normal regions within a solar image and statistical probability model of massive normal solar images.The proposed model,namely mixed convolution network(MCNet),is established over conditional generative adversarial network(GAN)and the combination of partial convolution(PC)and validness migratable convolution(VMC).These two convolutions were originally proposed for image inpainting.In addition,they are implemented only on unsaturated/valid pixels,followed by certain compensation to compensate the deviation of PC/VMC relative to normal convolution.Experimental results demonstrate that the proposed MCNet achieves favorable desaturated results for solar images and outperforms the state-of-the-art methods both quantitatively and qualitatively.展开更多
An algorithm was developed for identifying and tracking a magnetic bright point, or bright point （BP） for short, observed in both the photosphere （G-band） and chromosphere （Ca II H）, as well as for pairing a pho...An algorithm was developed for identifying and tracking a magnetic bright point, or bright point （BP） for short, observed in both the photosphere （G-band） and chromosphere （Ca II H）, as well as for pairing a photospheric BP （PBP） with its conjugate chromospheric BP （CBP）. Two sets of data observed by Hinode/SOT in the quiet Sun near the disk center were analyzed. About 278 PBP-CBP pairs were identified and tracked. Lifetimes of both the PBPs and CBPs follow an exponential distribution with average lifetimes of 174 s and 163 s, respectively. We found that the differences in appearance time, in disappearance time and in lifetime of the two kinds of BPs all follow Gaussian distributions,which may indicate that the mechanisms of PBP and CBP formation/disintegration are different. However, the lifetimes of PBPs and CBPs are positively correlated with one another, with a correlation coefficient of 0.8. Furthermore, we calculated the horizontal displacement between the PBP and its conjugate CBP, which follows a Gaussian function with an average and standard deviation of （67.7 ± 38.5）km. We also calculated the amplitude of the flux tube shape change which might be caused by MHD waves propagating along the flux tube, and found that it follows an exponential distribution very well.展开更多
New high-resolution echelle spectra of six single late-type Pleiades-like stars （V368 Cep, EP Eri, DX Leo, GJ 211, PW And and V383 Lac） were obtained with the 2.16 meter telescope at Xinglong Station in 2008-2010. U...New high-resolution echelle spectra of six single late-type Pleiades-like stars （V368 Cep, EP Eri, DX Leo, GJ 211, PW And and V383 Lac） were obtained with the 2.16 meter telescope at Xinglong Station in 2008-2010. Using the spectral subtraction technique, we analyzed our spectroscopic data and calculated the equiva- lent widths of excess emission from several indicators of chromospheric activity （Na I D1, D2, Hoz and Ca II infrared triplet lines）. All our results using chromospheric activ- ity indicators confirmed the previous findings. In addition, the maximum amplitudes of chromospheric rotational modulation and the ratio of EW8542/EW8498 were found to rise with increasing v sin i velocity.展开更多
We analyze oscillation behaviours in chromospheric internetwork regions using spectral observations of the C<SUB>II</SUB> 1334 ? line obtained with the Solar Ultraviolet Measurements of Emitted Radiation s...We analyze oscillation behaviours in chromospheric internetwork regions using spectral observations of the C<SUB>II</SUB> 1334 ? line obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) aboard Solar and Heliospheric Observatory (SOHO). Three areas, 26×120arcsec<SUP>2</SUP> each, at the various latitudes from the disk center to the north polar coronal hole, were rastered with a cadence of about 40–60 s in the solar minimum year. We obtained the time evolution of two-dimensional (2D) line intensity, continuum and line core shift. The continuum and the line shift show ~3 min chromospheric oscillations in the internetwork regions underlying the coronal hole as well as at the disk center. We find that the C<SUB>II</SUB> 1334 ? line shift oscillates with an average speed of ~1.7km<SUP>-1</SUP>, independent of the latitude, while its coherent scale decreases with latitude. On the other hand, the oscillation amplitude of the continuum around the 1334 ? and the phase delay between the Doppler shift and continuum slightly increase with latitude.展开更多
We attempt to propose a method for automatically detecting the solar filament chirality and barb beating. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm...We attempt to propose a method for automatically detecting the solar filament chirality and barb beating. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line （PIL） shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Ha filtergrams from the Big Bear Solar Observatory （BBSO） Ha archive and magnetograms observed with the Helioseismic and Magnetic Imager （HMI） on board the Solar Dynamics Observatory （SDO）. Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere （northern hemisphere） mainly have left-bearing （fight- bearing） barbs and positive （negative） magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid. The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations.展开更多
Ellerman bombs （EBs） are small brightening events in the solar lower atmosphere. By their original definition, the main characteristic of EBs is the two emission bumps in both wings of chro- mospheric lines, such a...Ellerman bombs （EBs） are small brightening events in the solar lower atmosphere. By their original definition, the main characteristic of EBs is the two emission bumps in both wings of chro- mospheric lines, such as Hα and Ca II 8542A lines. Up to now, most authors have found that the temperature increase of EBs around the temperature minimum region is in the range of 600-3000 K. However, with recent IRIS observations, some authors proposed that the temperature increase of EBs could be more than 10 000 K. Using non-LTE semi-empirical modeling, we investigate the line profiles, continuum emission and radiative losses for EB models with different temperature increases, and com- pare them with observations. Our result indicates that if the EB maximum temperature reaches more than 10000K around the temperature minimum region, then the resulting Hα and Call 8542A line profiles and the continuum emission would be much stronger than those of EB observations. Moreover, due to the high radiative losses, a high temperature EB compatible with observations. Thus, our study does not higher than 10 000 K. would have a very short lifetime, which is not support the proposal that EB temperatures are higher than 10 000 K.展开更多
Using the multi-wavelength data from the Atmospheric Imaging Assembly （AIA） onboard the Solar Dynamics Observatory （SDO） spacecraft, we study a jet occurring in a coronal hole near the northern pole of the Sun. Th...Using the multi-wavelength data from the Atmospheric Imaging Assembly （AIA） onboard the Solar Dynamics Observatory （SDO） spacecraft, we study a jet occurring in a coronal hole near the northern pole of the Sun. The jet presented distinct upward helical motion during ejection. By tracking six identified moving features （MFs） in the jet, we found that the plasma moved at an approximately constant speed along the jet＇s axis. Meanwhile, the MFs made a circular motion in the plane transverse to the axis. Inferred from linear and trigonometric fittings to the axial and transverse heights of the six tracks, the mean values of the axial velocities, transverse velocities, angular speeds, rotation periods, and rotation radii of the jet are 114 km s-1, 136 km s-1, 0.81° s-1, 452 s and 9.8 × 10^3 km respectively. As the MFs rose, the jet width at the corresponding height increased. For the first time, we derived the height variation of the longitudinal magnetic field strength in the jet from the assumption of magnetic flux conservation. Our results indicate that at heights of 1 × 10^4 -7 × 10^4 km from the base of the jet, the flux density in the jet decreases from about 15 to 3 G as a function of B = 0.5（R/R） - 1）-0.84 （G）. A comparison was made with other results in previous studies.展开更多
Ellerman bombs （EBs） are tiny brightenings often observed near sunspots. The most impressive characteristic of EB spectra is the two emission bumps in both wings of the Hα and Ca II 8542 A lines. High-resolution sp...Ellerman bombs （EBs） are tiny brightenings often observed near sunspots. The most impressive characteristic of EB spectra is the two emission bumps in both wings of the Hα and Ca II 8542 A lines. High-resolution spectral data of three small EBs were obtained on 2013 June 6 with the largest solar telescope, the 1.6 m New Solar Telescope at the Big Bear Solar Observatory. The characteristics of these EBs are analyzed. The sizes of the EBs are in the range of 0.3＂ - 0.8＂ and their durations are only 3-5 min. Our semi-empirical atmospheric models indicate that the heating occurs around the temperature minimum region with a temperature increase of 2700- 3000 K, which is surprisingly higher than previously thought. The radiative and kinetic energies are estimated to be as high as 5 × 1025 - 3.0 × 10^26 erg despite the small size of these EBs. Observations of the magnetic field show that the EBs just appeared in a parasitic region with mixed polarities and were accompanied by mass motions. Nonlinear force-free field extrapolation reveals that the three EBs are connected with a series of magnetic field lines associated with bald patches, which strongly implies that these EBs should be produced by magnetic reconnection in the solar lower atmosphere. According to the lightcurves and the estimated magnetic reconnection rate, we propose that there is a three phase process in EBs： pre-heating, flaring and cooling phases.展开更多
基金the National Natural Science Foundation of China(NSFC,Grant Nos.11527804,U1931206,11373065,11078005,10943002 and 12003066)。
文摘This paper presents the analytical results of solar MgⅠb_(2)flash spectra,obtained by the prototype Fiber Arrayed Solar Optic Telescope in process of the 2013 Gabon total solar eclipse.The analysis reveals irregular distributions of the spectral line parameters like ratio of line source function to continuum oneβ,ratio of line emissivity to continuum emissivityζ,ratio of the continuum opacity to the line opacity r_(0),line center optical depthτ_(0)、,the line widthΔλ_(D),and the line-of-sight velocity v_(los),while the approximately spherical symmetry can be found in the maps of integrated line intensity and continuum intensity.These irregular distributions originate from those of line profile features like the maximum intensity,the line width and line center wavelength.It is also found from the recovered line center optical depthτ_(0) that in the middle chromosphere,the optical depth is not small due to nonignorable absorption and the long light path along the line-of-sight.Finally,we show that the excessive broadening of spectral lines can be due to co-existence of multiple radiative sources with different line-of-sight velocities unresolved in one detector pixel.
基金supported by the National Natural Science Foundation of China(NSFC)under grant No.12233012,the Strategic Priority Research Program of the Chinese Academy of Sciences,grant No.XDB0560102the National Key R&D Program of China 2022YFF0503003(2022YFF0503000)。
文摘The in-flight calibration and performance of the Solar Disk Imager(SDI),which is a pivotal instrument of the LyαSolar Telescope onboard the Advanced Space-based Solar Observatory mission,suggested a much lower spatial resolution than expected.In this paper,we developed the SDI point-spread function(PSF)and Image Bivariate Optimization Algorithm(SPIBOA)to improve the quality of SDI images.The bivariate optimization method smartly combines deep learning with optical system modeling.Despite the lack of information about the real image taken by SDI and the optical system function,this algorithm effectively estimates the PSF of the SDI imaging system directly from a large sample of observational data.We use the estimated PSF to conduct deconvolution correction to observed SDI images,and the resulting images show that the spatial resolution after correction has increased by a factor of more than three with respect to the observed ones.Meanwhile,our method also significantly reduces the inherent noise in the observed SDI images.The SPIBOA has now been successfully integrated into the routine SDI data processing,providing important support for the scientific studies based on the data.The development and application of SPIBOA also paves new ways to identify astronomical telescope systems and enhance observational image quality.Some essential factors and precautions in applying the SPIBOA method are also discussed.
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.
文摘Using the new soft X-ray data from the Macao Science Satellite-1,we studied a solar flare that occurred on 22 June 2023.We found that the centroids of the Ca(around 3.9 keV)and Fe(around 6.7 keV)line features exhibit a rapid shift toward higher energy channels during the flare's rising phase,followed by a gradual decrease during the decay phase.Through precise energy calibration,the centroids are determined with high accuracy.Temperature and velocity are then self-consistently derived by comparing the centroids with those calculated from the synthesized line features using the latest CHIANTI atomic database(ver.10.1).The calculated maximum velocity reaches up to 710±60 km s-1,which significantly exceeds the previously reported values.Our results suggest that the entire shift of soft X-ray lines may occur during the process of chromospheric evaporation.
基金Project supported by Academia Sinica under contract 87-64.
文摘The data of velocity and magnetic fields in the solar photosphere (5324 A) and thechromosphere (4861 A) clearly show the features of tangential discontinuity of velocity inthe chromosphere. The velocity fields in and near the solar active region named No. 88029by the Huairou Station have been analyzed in detail. A lot of magnetohydrodynamic discon-tinuous surfaces, especially the tangential discontinuities, are shown from the observations.The calculations of the thickness of discontinuous layer and the evoluiton time of instabilityagree with the observational results. The variations of the flow field will directly influencethe evolutions and changes of the active region as the magnetic field are coupled closelywith the plasma motion.
基金support by the Astronomical station Vidojevica,funding from the Ministry of Science,Technological Development and Innovation of the Republic of Serbia(contract No.451-03-66/2024-03/200002)by the EC through project BELISSIMA(call FP7-REGPOT-2010-5,No.265772)financed by Silesian University of Technology Statutory Activities grant No.BK-250/RAu-11/2024。
文摘Low mass ratio contact binary systems are more likely to have unstable orbits and potentially merge.In addition,such systems exhibit characteristics such as starspots and high energy emissions(UV)suggestive of chromospheric and magnetic activity.Light curve modeling of ten contact binary systems is reported.All were found to be of extreme low mass ratio ranging from 0.122 to 0.24 and three were found to be potentially unstable and possible merger candidates.Filling of the infrared calcium absorption lines is a marker of increased chromospheric activity.We use the available Large Sky Area Multi-Object Fiber Spectroscopic Telescope spectra along with matched standard spectra(broadened for rotation)to measure the excess filling of the central core depression flux of the two main infrared calcium absorption linesλ8542 andλ8662.We find that all reported contact binaries have excess filling of the core flux in the infrared calcium lines.Three of the systems reported were also observed by the Galaxy Evolution Explorer mission and we find that all three have features of excess ultraviolet emissions further adding evidence for increased chromospheric activity in low mass ratio contact binaries.Analysis of both orbital stability and absorption line filling is dependent on the determination of geometric and absolute parameters from light curve modeling.Not an insignificant number of contact binary light curves exhibit the O’Connell effect,usually attributed to starspots.We discuss the inclusion of starspots in light curve solutions and how they influence the geometric and absolute parameters.
基金the University Grants Commission,India for providing a Non-NET fellowship。
文摘We study the nonlinear coupling of kinetic Alfvén waves with ion acoustic waves applicable to the Earth’s radiation belt and near-Sun streamer belt solar wind using dynamical equations in the form of modified Zakharov systems.Numerical simulations show the formation of magnetic field filamentary structures associated with density humps and dips which become turbulent at later times,redistributing the energy to higher wavenumbers.The magnetic power spectra exhibit an inertial range Kolmogorov-like spectral index value of-5/3 for k_(⊥)ρ_(i)<1 followed by a steeper dissipation range spectra with indices~-3 for the radiation belt case and~-4 for the nearSun streamer belt solar wind case,here k_(⊥)andρ_(i)represent the wavevector component perpendicular to the background magnetic field and the ion thermal gyroradius,respectively.Applying quasilinear theory in terms of the Fokker-Planck equation in the region of wavenumber turbulent spectra,we find the particle distribution function flattening in the superthermal tail population which is the signature of particle energization and plasma heating.
基金Supported by the National Natural Science Foundation of China under Grant Nos 40274050 and 40336052, and the National Key Basic Research Special Foundation of China under Grant No G2000078405.
文摘The characteristics of magnetohydrodynamic fast wave propagation in the solar stratified atmosphere are studied by the ray tracing method. The propagation behaviour of the wavefronts is described in detail. A magnetic field incorporating the characteristics field spreading expected in flux tubes is used, which represents the main feature of an active region. Partly ionization is considered beside the stratified solar atmosphere consisting chromosphere, transition region and corona. The study may explain the characteristics in observations of Moreton and extraultraviolet image telescope （EIT） waves. The wavefront incurred by the disturbance initialized at the base of the transition region propagates fast initially due to strong magnetic field, and it slows down when arriving beyond the region of flux-tube. Meanwhile, the wave propagates in the corona with a more consistent speed, as seen in the observation of EIT waves. The speeds and propagated characteristics in chromosphere and corona of the wavefronts are in agreement with those observed in H~ Moreton and EIT waves, respectively.
基金partially supported by the National Natural Science Foundation of China (Grant No. 11103075)the West Light Foundation of Chinese Academy of Sciences
文摘The Multi-wavelength Spectrometer is a medium-dispersion（R^130 000）grating spectrometer installed on the New Vacuum Solar Telescope at the Fuxian Solar Observatory,Yunnan Astronomical Observatory,Chinese Academy of Sciences.It is designed to accurately observe the velocity and magnetic fields of the Sun.The present configuration of this spectrometer allows us to simultaneously observe three different solar spectral lines.This work is dedicated to showing the first observations carried out in both the Hαand Ca II 8542 A lines.We give a detailed description of the data reduction process,focusing on the retrieval of a flat field from the high-resolution spectral data.Two different methods are also performed and compared to eliminate the residual fringe in the reduced data.The real spectral resolution and instrumental profile are analyzed based on the final results,which indicate that this spectrometer presently satisfies the expected performance and it is ready for further scientific observations.
基金supported by the National Natural Science Foundation of China (Nos. U1231205,11163004,11263004 and 11303011)the Open Research Program of Key Laboratory of Solar Activity of Chinese Academy of Sciences (No. KLSA201309)supported by the Opening Project of Key Laboratory of Astronomical Optics&Technology,Nanjing Institute of Astronomical Optics & Technology,Chinese Academy of Sciences (No. CAS-KLAOT-KF201306)
文摘The emission sources of umbral flashes （UFs） are believed to be closely related to running umbral and penumbral waves, and are concluded to be associated with umbral dots in the solar photosphere. Accurate identification of emission sources of UFs is crucial for investigating these physical phenomena and their inherent relationships. A relatively novel model of shape perception, namely phase congruency （PC）, uses phase information in the Fourier domain to identify the geometrical shape of the region of interest in different intensity levels, rather than intensity or gradient. Previous studies indicate that the model is suitable for identifying features with low contrast and low luminance. In the present paper, we applied the PC model to identify the emission sources of UFs and to locate their positions. For illustrating the high performance of our proposed method, two time sequences of Ca n H images derived from the Hinode/SOT on 2010 August 10 and 2013 August 20 were used. Furthermore, we also compared these results with the analysis results that are identified by the traditional/classical identification methods, including the gray-scale adjusted technique and the running difference technique. The result of our analysis demonstrates that our proposed method is more accurate and effective than the traditional identification methods when applied to identifying the emission sources of UFs and to locating their positions.
基金sponsored by the National Natural Science Foundation of China (NSFC) under Grant Nos.11873027, U2031140, 12073077, 11833010 and 11973088West Light Foundation of the Chinese Academy of Sciences (Y9XB01A and Y9XB019)。
文摘Suppressing the interference of atmospheric turbulence and obtaining observation data with a high spatial resolution are an issue to be solved urgently for ground observations. One way to solve this problem is to perform a statistical reconstruction of short-exposure speckle images. Combining the rapidity of Shift-Add and the accuracy of speckle masking, this paper proposes a novel reconstruction algorithm-NASIR(Non-rigid Alignment based Solar Image Reconstruction). NASIR reconstructs the phase of the object image at each frequency by building a computational model between geometric distortion and intensity distribution and reconstructs the modulus of the object image on the aligned speckle images by speckle interferometry. We analyzed the performance of NASIR by using the correlation coefficient, power spectrum, and coefficient of variation of intensity profile in processing data obtained by the NVST(1 m New Vacuum Solar Telescope). The reconstruction experiments and analysis results show that the quality of images reconstructed by NASIR is close to speckle masking when the seeing is good, while NASIR has excellent robustness when the seeing condition becomes worse. Furthermore, NASIR reconstructs the entire field of view in parallel in one go, without phase recursion and block-by-block reconstruction, so its computation time is less than half that of speckle masking. Therefore, we consider NASIR is a robust and highquality fast reconstruction method that can serve as an effective tool for data filtering and quick look.
基金Support for the post-launch operation is provided by JAXA and NAOJ (Japan), STFC (UK), NASA (USA), ESA and NSC (Norway)financial the German Science Foundation (DFG) under grant DE 787/3-1
文摘We present properties of intensity oscillations of a sunspot in the photo- sphere and chromosphere using G band and Ca u H filtergrams from Hinode. Intensity power maps as function of magnetic field strength and frequency reveal reduction of power in the G band with an increase in photospheric magnetic field strength at all frequencies. In Ca II H, however, stronger fields exhibit more power at high frequen- cies, particularly in the 4.5-8.0 mHz band. Power distributions in different locations of the active region show that the oscillations in Ca II H exhibit more power compared to that of the G band. We also relate the power in intensity oscillations with differ- ent components of the photospheric vector magnetic field using near simultaneous spectro-polarimetric observations of the sunspot from the Hinode spectropolarime- ter. The photospheric umbral power is strongly anti-correlated with the magnetic field strength and its line-of-sight component but there is a good correlation with the trans- verse component. A reversal of this trend is observed in the chromosphere except at low frequencies （V≤ 1.5 mHz）. The power in sunspot penumbrae is anti-correlated with the magnetic field parameters at all frequencies （1.0 ≤ v ≤ 8.0 mHz） in both the photosphere and chromosphere, except that the chromospheric power shows a strong correlation in the frequency range 3-3.5 mHz.
基金supported by the Peng Cheng Laboratory Cloud Brain(No.PCL2021A13)the National Natural Science Foundation of China(NSFC)under 11790305,11973058 and 12103064。
文摘The Atmospheric Imaging Assembly(AIA)onboard the Solar Dynamics Observatory(SDO)provides full-disk solar images with high temporal cadence and spatial resolution over seven extreme ultraviolet(EUV)wave bands.However,as violent solar flares happen,images captured in EUV wave bands may have saturation in active regions,resulting in signal loss.In this paper,we propose a deep learning model to restore the lost signal in saturated regions by referring to both unsaturated/normal regions within a solar image and statistical probability model of massive normal solar images.The proposed model,namely mixed convolution network(MCNet),is established over conditional generative adversarial network(GAN)and the combination of partial convolution(PC)and validness migratable convolution(VMC).These two convolutions were originally proposed for image inpainting.In addition,they are implemented only on unsaturated/valid pixels,followed by certain compensation to compensate the deviation of PC/VMC relative to normal convolution.Experimental results demonstrate that the proposed MCNet achieves favorable desaturated results for solar images and outperforms the state-of-the-art methods both quantitatively and qualitatively.
基金supported by the CAS grants(XDA17010507,XDA15010900 and QYZDJ-SSWSLH012)the NationalBasic Research Program of China(973 Program,2013CBA01503)+1 种基金the National Natural Science Foundation of China(Grant Nos.U1631130,11333007 and 11763004)supported by a grant associated with the Project of the Group for Innovation of Yunnan Province
文摘An algorithm was developed for identifying and tracking a magnetic bright point, or bright point （BP） for short, observed in both the photosphere （G-band） and chromosphere （Ca II H）, as well as for pairing a photospheric BP （PBP） with its conjugate chromospheric BP （CBP）. Two sets of data observed by Hinode/SOT in the quiet Sun near the disk center were analyzed. About 278 PBP-CBP pairs were identified and tracked. Lifetimes of both the PBPs and CBPs follow an exponential distribution with average lifetimes of 174 s and 163 s, respectively. We found that the differences in appearance time, in disappearance time and in lifetime of the two kinds of BPs all follow Gaussian distributions,which may indicate that the mechanisms of PBP and CBP formation/disintegration are different. However, the lifetimes of PBPs and CBPs are positively correlated with one another, with a correlation coefficient of 0.8. Furthermore, we calculated the horizontal displacement between the PBP and its conjugate CBP, which follows a Gaussian function with an average and standard deviation of （67.7 ± 38.5）km. We also calculated the amplitude of the flux tube shape change which might be caused by MHD waves propagating along the flux tube, and found that it follows an exponential distribution very well.
基金Supported by the National Natural Science Foundation of China
文摘New high-resolution echelle spectra of six single late-type Pleiades-like stars （V368 Cep, EP Eri, DX Leo, GJ 211, PW And and V383 Lac） were obtained with the 2.16 meter telescope at Xinglong Station in 2008-2010. Using the spectral subtraction technique, we analyzed our spectroscopic data and calculated the equiva- lent widths of excess emission from several indicators of chromospheric activity （Na I D1, D2, Hoz and Ca II infrared triplet lines）. All our results using chromospheric activ- ity indicators confirmed the previous findings. In addition, the maximum amplitudes of chromospheric rotational modulation and the ratio of EW8542/EW8498 were found to rise with increasing v sin i velocity.
基金Supported by the National Natural Science Foundation of China.
文摘We analyze oscillation behaviours in chromospheric internetwork regions using spectral observations of the C<SUB>II</SUB> 1334 ? line obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) aboard Solar and Heliospheric Observatory (SOHO). Three areas, 26×120arcsec<SUP>2</SUP> each, at the various latitudes from the disk center to the north polar coronal hole, were rastered with a cadence of about 40–60 s in the solar minimum year. We obtained the time evolution of two-dimensional (2D) line intensity, continuum and line core shift. The continuum and the line shift show ~3 min chromospheric oscillations in the internetwork regions underlying the coronal hole as well as at the disk center. We find that the C<SUB>II</SUB> 1334 ? line shift oscillates with an average speed of ~1.7km<SUP>-1</SUP>, independent of the latitude, while its coherent scale decreases with latitude. On the other hand, the oscillation amplitude of the continuum around the 1334 ? and the phase delay between the Doppler shift and continuum slightly increase with latitude.
基金supported by NKBRSF (Grant Nos.2011CB811402 and 2014CB744203)the National Natural Science Foundation of China (Grant Nos.11203014,11533005 and 11025314)the grants from CSC201306190046 and CXZZ130041
文摘We attempt to propose a method for automatically detecting the solar filament chirality and barb beating. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line （PIL） shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Ha filtergrams from the Big Bear Solar Observatory （BBSO） Ha archive and magnetograms observed with the Helioseismic and Magnetic Imager （HMI） on board the Solar Dynamics Observatory （SDO）. Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere （northern hemisphere） mainly have left-bearing （fight- bearing） barbs and positive （negative） magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid. The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11533005,11025314,13001003,11203014 and 11103075)NKBRSF(Grant 2014CB744203)
文摘Ellerman bombs （EBs） are small brightening events in the solar lower atmosphere. By their original definition, the main characteristic of EBs is the two emission bumps in both wings of chro- mospheric lines, such as Hα and Ca II 8542A lines. Up to now, most authors have found that the temperature increase of EBs around the temperature minimum region is in the range of 600-3000 K. However, with recent IRIS observations, some authors proposed that the temperature increase of EBs could be more than 10 000 K. Using non-LTE semi-empirical modeling, we investigate the line profiles, continuum emission and radiative losses for EB models with different temperature increases, and com- pare them with observations. Our result indicates that if the EB maximum temperature reaches more than 10000K around the temperature minimum region, then the resulting Hα and Call 8542A line profiles and the continuum emission would be much stronger than those of EB observations. Moreover, due to the high radiative losses, a high temperature EB compatible with observations. Thus, our study does not higher than 10 000 K. would have a very short lifetime, which is not support the proposal that EB temperatures are higher than 10 000 K.
基金supported by the National Natural Science Foundation of China(Grant Nos.11103090,11025315,40890161,10921303,40825014, and 40890162)the CAS project KJCX2-YW-T04,the National Basic Research Program of China (973 Program,No.2011CB811403)the Shandong Provincial Natural Science Foundation, China(ZR 2011AQ009)
文摘Using the multi-wavelength data from the Atmospheric Imaging Assembly （AIA） onboard the Solar Dynamics Observatory （SDO） spacecraft, we study a jet occurring in a coronal hole near the northern pole of the Sun. The jet presented distinct upward helical motion during ejection. By tracking six identified moving features （MFs） in the jet, we found that the plasma moved at an approximately constant speed along the jet＇s axis. Meanwhile, the MFs made a circular motion in the plane transverse to the axis. Inferred from linear and trigonometric fittings to the axial and transverse heights of the six tracks, the mean values of the axial velocities, transverse velocities, angular speeds, rotation periods, and rotation radii of the jet are 114 km s-1, 136 km s-1, 0.81° s-1, 452 s and 9.8 × 10^3 km respectively. As the MFs rose, the jet width at the corresponding height increased. For the first time, we derived the height variation of the longitudinal magnetic field strength in the jet from the assumption of magnetic flux conservation. Our results indicate that at heights of 1 × 10^4 -7 × 10^4 km from the base of the jet, the flux density in the jet decreases from about 15 to 3 G as a function of B = 0.5（R/R） - 1）-0.84 （G）. A comparison was made with other results in previous studies.
基金supported by the National Natural Science Foundation of China (NSFC, Grants 10878002, 10933003, 11025314, 10673004, 11203014 and 11103075)NKBRSF (Grant Nos. 2011CB811402 and 2014CB744203)+1 种基金the support of the US NSF (AGS0847126 and AGS-1250818)NASA (NNX13AG14G)
文摘Ellerman bombs （EBs） are tiny brightenings often observed near sunspots. The most impressive characteristic of EB spectra is the two emission bumps in both wings of the Hα and Ca II 8542 A lines. High-resolution spectral data of three small EBs were obtained on 2013 June 6 with the largest solar telescope, the 1.6 m New Solar Telescope at the Big Bear Solar Observatory. The characteristics of these EBs are analyzed. The sizes of the EBs are in the range of 0.3＂ - 0.8＂ and their durations are only 3-5 min. Our semi-empirical atmospheric models indicate that the heating occurs around the temperature minimum region with a temperature increase of 2700- 3000 K, which is surprisingly higher than previously thought. The radiative and kinetic energies are estimated to be as high as 5 × 1025 - 3.0 × 10^26 erg despite the small size of these EBs. Observations of the magnetic field show that the EBs just appeared in a parasitic region with mixed polarities and were accompanied by mass motions. Nonlinear force-free field extrapolation reveals that the three EBs are connected with a series of magnetic field lines associated with bald patches, which strongly implies that these EBs should be produced by magnetic reconnection in the solar lower atmosphere. According to the lightcurves and the estimated magnetic reconnection rate, we propose that there is a three phase process in EBs： pre-heating, flaring and cooling phases.
