We present a method of 13 late-type main-sequence stars chromospheric flux observation data calculations. These Sun-like stars have well-determined cyclic flux variations similar to the 11-year solar activity cycle. O...We present a method of 13 late-type main-sequence stars chromospheric flux observation data calculations. These Sun-like stars have well-determined cyclic flux variations similar to the 11-year solar activity cycle. Our flux prediction is based on chromospheric HK emission time series measurements from the Mount Wilson Observatory and comparable solar data. We show that solar three - component modeling explains well the stellar observations. We find that the 10 - 20% of K - stars disc’s surfaces are occupied by bright active regions.展开更多
We present the research results on new CCD spectroscopic observations of three chromospherically active binary stars (BY Dra class), which were obtained by means of Coude echelle spectrograph fed by the 2 16m telescop...We present the research results on new CCD spectroscopic observations of three chromospherically active binary stars (BY Dra class), which were obtained by means of Coude echelle spectrograph fed by the 2 16m telescope at Beijing Astronomical Observatory. These spectrum images were reduced according to the standard fashion using IRAF package. With the aid of stellar model atmosphere, we have analyzed these spectra and derived the average metal abundance and Li abundance of three systems. Using two special spectral lines, we have also discussed the chromospheric activity indicators of them.展开更多
Up to now, exact measurements of chromospheric magnetic fields have not been as successful as those done in the photosphere. We are currently engaging in diagnostics of chromospheric magnetic fields with the Mg b2 lin...Up to now, exact measurements of chromospheric magnetic fields have not been as successful as those done in the photosphere. We are currently engaging in diagnostics of chromospheric magnetic fields with the Mg b2 line by employing the Multi-Channel Solar Telescope at Huairou Solar Observing Station. Therefore, how to improve accuracy in the measurement is the main issue of our present study. To this end, we first study linear calibration coefficients for longitudinal and transverse components of chromospheric fields, which vary with wavelength, in the case of a weak field assumption. Then the polarization crosstalk introduced by instruments is analyzed in detail with two numerical simulation methods. Comparisons of the po- larization signals between cases with and without correction are presented. The result indicates that polarization accuracy is greatly improved after crosstalk correction.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
The distribution or wavelength-dependence of the formation regions of frequently used solar lines, Hα, Hβ, CaIIH and Car18542, in quiet Sun, faint and bright flares is explored in the unpolarized case. We stress fou...The distribution or wavelength-dependence of the formation regions of frequently used solar lines, Hα, Hβ, CaIIH and Car18542, in quiet Sun, faint and bright flares is explored in the unpolarized case. We stress four aspects characterising the property of line formation process: 1) width of line formation core; 2) line formation region; 3) influence of the temperature minimum region; and 4) wavelength ranges within which one can obtain pure chromospheric and photospheric filtergrams. It is shown that the above four aspects depend strongly on the atmospheric physical condition and the lines used. The formation regions of all the wavelength points within a line may be continuously distributed over one depth domain or discretely distributed because of no contribution coming from the temperature minimum region, an important domain in the solar atmosphere that determines the distribution pattern of escape photons. Cm the other hand, the formation region of one wavelength point may cover only one heigh t range or spread over two domains which are separated again by the temperature minimum region. Different lines may form in different regions in the quiet Sun. However, these line formation regions become closer in solar flaring regions. Finally, though the stratification of line-of-sight velocity can alter the position of the line formation core within the line band and result in the asymmetry of the line formation core about the shifted line center, it can only lead to negligible changes in the line formation region or the line formation core width. All these results can be instructive to solar filtering observations.展开更多
We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing ...We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. The chromospheric and photospheric magnetograms together with Hβ filtergrams of the filament were examined. The filament was located on the neutral line of the large scale longitudinal magnetic field in the photosphere and the chromosphere. The lateral feet of the filament were found to be related to magnetic structures with opposite polarities. Two small lateral feet are linked to weak parasitic polarity. There is a negative magnetic structure in the photosphere under a break of the filament. At the location corresponding to the filament in the chromospheric magnetograms, the magnetic strength is found to be about 40-70 Gauss (measuring error about 39 Gauss). The magnetic signal indicates the amplitude and orientation of the internal magnetic field in the filament. We discuss several possible causes which may produce such a measured signal. A twisted magnetic configuration inside the filament is suggested .展开更多
The observations and identifications of the chromospheric evaporation of solar flares during the 21st solar peak years are considered a great discovery in the history of solar physics. In order to explain the process ...The observations and identifications of the chromospheric evaporation of solar flares during the 21st solar peak years are considered a great discovery in the history of solar physics. In order to explain the process of chromospheric evaporation,many hydrodynamical models of solar flares have been proposed. These models can explain chromospheric evaporation and predict that there should exist some chromospheric material moving downward, responding to the flare energy release. This downward moving chromospheric material, usually named chromospheric condensation, has a展开更多
We examine chromospheric oscillations in both a coronal hole (CH) and a quiet Sun (QS) region, by employing Transition Region and Coronal Explorer (TRACE) and Big Bear Solar Observatory (BBSO) data on September 14 and...We examine chromospheric oscillations in both a coronal hole (CH) and a quiet Sun (QS) region, by employing Transition Region and Coronal Explorer (TRACE) and Big Bear Solar Observatory (BBSO) data on September 14 and 16, 2004. For the CH, the average oscillation periods of network magnetic field and non-magnetic field (NMF) regions are 257 and 222 s, respectively, and the average period of network field is longer than that of NMF region by 15.8%. In the QS, the average oscillation period is the 225 s for network field and 212 s for the NMF region. The average period of the network field is also longer than that of the NMF region by 6.1%. For the network region, we find that the average period in the CH is longer than that in the QS by 14.2%. This difference between CH and QS is possibly caused by different magnetic configurations i.e. the open magnetic field in the CH and the close field in the QS.展开更多
This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospher...This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic fields. Some questions in the study of the chromospheric magnetic field are also presented.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 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
We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stell...We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle.展开更多
Ⅴ band photometry of three RS CVn stars,Ⅱ Peg, IM Peg and UX Ari, is carried out to study the physical properties of these variables. We verified the significant and regular optical photometric variability to be pre...Ⅴ band photometry of three RS CVn stars,Ⅱ Peg, IM Peg and UX Ari, is carried out to study the physical properties of these variables. We verified the significant and regular optical photometric variability to be present in all three stars. The strong photometric variability and emission of Hα and Ca Ⅱ H ＆ K using high resolution optical spectroscopy with the Hanle Echelle Spectrograph （HESP）, which operates in conjunction with the Himalayan Chandra Telescope, verify the strong chromospheric activity which is present in RS CVn stars. The photometric studies of Ⅱ Peg, UX Ari and IM Peg were subjected to light curve analysis for spot parameters using a two-starspot model.展开更多
During total solar eclipses, we can observe the outer atmospheric layers of the sun (chromosphere and corona). The solar corona extends to several solar radii depending on the sunspot cycle. Basic coronal structures s...During total solar eclipses, we can observe the outer atmospheric layers of the sun (chromosphere and corona). The solar corona extends to several solar radii depending on the sunspot cycle. Basic coronal structures such as polar streamers, helmet type structures were?observed?during the 2006 total solar eclipse. Our total solar eclipse 2006 observations through?both White light corona and H-Alpha filter allowed us to describe coronal structures and Prominence Activity. We found that the solar corona is extended to 4 times of solar radii, the existence different zones of white light corona were shown, moreover, we compared the defined features of solar corona at different observing locations along the track of total solar eclipse 2006. The solar limb activity was studied during both of partial and total eclipse phases by using H-Alpha and white light observations from Salloum, Egypt. We got same prominence activity during partial and total phases of the solar eclipse and recorded three prominences on solar limb. Finally, our processed image in a good agreement with the published?processed images?was?observed from different locations along the track of total eclipse,?added, similar magnetic field structure shown in our processed image and published one.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
文摘We present a method of 13 late-type main-sequence stars chromospheric flux observation data calculations. These Sun-like stars have well-determined cyclic flux variations similar to the 11-year solar activity cycle. Our flux prediction is based on chromospheric HK emission time series measurements from the Mount Wilson Observatory and comparable solar data. We show that solar three - component modeling explains well the stellar observations. We find that the 10 - 20% of K - stars disc’s surfaces are occupied by bright active regions.
文摘We present the research results on new CCD spectroscopic observations of three chromospherically active binary stars (BY Dra class), which were obtained by means of Coude echelle spectrograph fed by the 2 16m telescope at Beijing Astronomical Observatory. These spectrum images were reduced according to the standard fashion using IRAF package. With the aid of stellar model atmosphere, we have analyzed these spectra and derived the average metal abundance and Li abundance of three systems. Using two special spectral lines, we have also discussed the chromospheric activity indicators of them.
基金Supported by the National Natural Science Foundation of China
文摘Up to now, exact measurements of chromospheric magnetic fields have not been as successful as those done in the photosphere. We are currently engaging in diagnostics of chromospheric magnetic fields with the Mg b2 line by employing the Multi-Channel Solar Telescope at Huairou Solar Observing Station. Therefore, how to improve accuracy in the measurement is the main issue of our present study. To this end, we first study linear calibration coefficients for longitudinal and transverse components of chromospheric fields, which vary with wavelength, in the case of a weak field assumption. Then the polarization crosstalk introduced by instruments is analyzed in detail with two numerical simulation methods. Comparisons of the po- larization signals between cases with and without correction are presented. The result indicates that polarization accuracy is greatly improved after crosstalk correction.
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Item 199730l6 of National Science Founda-tion of China and National Major Project 973 under the grant G2000078401. The authors
文摘The distribution or wavelength-dependence of the formation regions of frequently used solar lines, Hα, Hβ, CaIIH and Car18542, in quiet Sun, faint and bright flares is explored in the unpolarized case. We stress four aspects characterising the property of line formation process: 1) width of line formation core; 2) line formation region; 3) influence of the temperature minimum region; and 4) wavelength ranges within which one can obtain pure chromospheric and photospheric filtergrams. It is shown that the above four aspects depend strongly on the atmospheric physical condition and the lines used. The formation regions of all the wavelength points within a line may be continuously distributed over one depth domain or discretely distributed because of no contribution coming from the temperature minimum region, an important domain in the solar atmosphere that determines the distribution pattern of escape photons. Cm the other hand, the formation region of one wavelength point may cover only one heigh t range or spread over two domains which are separated again by the temperature minimum region. Different lines may form in different regions in the quiet Sun. However, these line formation regions become closer in solar flaring regions. Finally, though the stratification of line-of-sight velocity can alter the position of the line formation core within the line band and result in the asymmetry of the line formation core about the shifted line center, it can only lead to negligible changes in the line formation region or the line formation core width. All these results can be instructive to solar filtering observations.
基金Supported by the National Natural Science Foundation of China.
文摘We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. The chromospheric and photospheric magnetograms together with Hβ filtergrams of the filament were examined. The filament was located on the neutral line of the large scale longitudinal magnetic field in the photosphere and the chromosphere. The lateral feet of the filament were found to be related to magnetic structures with opposite polarities. Two small lateral feet are linked to weak parasitic polarity. There is a negative magnetic structure in the photosphere under a break of the filament. At the location corresponding to the filament in the chromospheric magnetograms, the magnetic strength is found to be about 40-70 Gauss (measuring error about 39 Gauss). The magnetic signal indicates the amplitude and orientation of the internal magnetic field in the filament. We discuss several possible causes which may produce such a measured signal. A twisted magnetic configuration inside the filament is suggested .
基金Project supported by the National Natural Science Foundation of China
文摘The observations and identifications of the chromospheric evaporation of solar flares during the 21st solar peak years are considered a great discovery in the history of solar physics. In order to explain the process of chromospheric evaporation,many hydrodynamical models of solar flares have been proposed. These models can explain chromospheric evaporation and predict that there should exist some chromospheric material moving downward, responding to the flare energy release. This downward moving chromospheric material, usually named chromospheric condensation, has a
基金Supported by the National Natural Science Foundation of China (Grant Nos. G10873020, 10603008, 40890161, 10703020, 40674081, and10703007)the CAS Project (Grant No. KJCX2-YW-T04)the National Basic Research Program of China (Grant No. G2006CB806303)
文摘We examine chromospheric oscillations in both a coronal hole (CH) and a quiet Sun (QS) region, by employing Transition Region and Coronal Explorer (TRACE) and Big Bear Solar Observatory (BBSO) data on September 14 and 16, 2004. For the CH, the average oscillation periods of network magnetic field and non-magnetic field (NMF) regions are 257 and 222 s, respectively, and the average period of network field is longer than that of NMF region by 15.8%. In the QS, the average oscillation period is the 225 s for network field and 212 s for the NMF region. The average period of the network field is also longer than that of the NMF region by 6.1%. For the network region, we find that the average period in the CH is longer than that in the QS by 14.2%. This difference between CH and QS is possibly caused by different magnetic configurations i.e. the open magnetic field in the CH and the close field in the QS.
基金the National Key Basic Research Science Foundation (NKBRSF) (Grant Nos. G200007840 , G2000078401) the National Natural Sciences Foundation of China (Grant Nos. 9791090 , 9791092).
文摘This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic fields. Some questions in the study of the chromospheric magnetic field are also presented.
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.
基金Funding for the TESS mission is provided by the NASA Explorer Program。
文摘We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle.
文摘Ⅴ band photometry of three RS CVn stars,Ⅱ Peg, IM Peg and UX Ari, is carried out to study the physical properties of these variables. We verified the significant and regular optical photometric variability to be present in all three stars. The strong photometric variability and emission of Hα and Ca Ⅱ H ＆ K using high resolution optical spectroscopy with the Hanle Echelle Spectrograph （HESP）, which operates in conjunction with the Himalayan Chandra Telescope, verify the strong chromospheric activity which is present in RS CVn stars. The photometric studies of Ⅱ Peg, UX Ari and IM Peg were subjected to light curve analysis for spot parameters using a two-starspot model.
文摘During total solar eclipses, we can observe the outer atmospheric layers of the sun (chromosphere and corona). The solar corona extends to several solar radii depending on the sunspot cycle. Basic coronal structures such as polar streamers, helmet type structures were?observed?during the 2006 total solar eclipse. Our total solar eclipse 2006 observations through?both White light corona and H-Alpha filter allowed us to describe coronal structures and Prominence Activity. We found that the solar corona is extended to 4 times of solar radii, the existence different zones of white light corona were shown, moreover, we compared the defined features of solar corona at different observing locations along the track of total solar eclipse 2006. The solar limb activity was studied during both of partial and total eclipse phases by using H-Alpha and white light observations from Salloum, Egypt. We got same prominence activity during partial and total phases of the solar eclipse and recorded three prominences on solar limb. Finally, our processed image in a good agreement with the published?processed images?was?observed from different locations along the track of total eclipse,?added, similar magnetic field structure shown in our processed image and published one.
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.
