Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the high...Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the higher coronal magnetic field intensity may correspond to.To try to further reveal the relationship between coronal green line brightness and magnetic field intensity,we use the 2 D coronal images observed by Yunnan Observatories Greenline Imaging System(YOGIS) of the 10 cm Lijiang coronagraph and the coronal magnetic field maps calculated from the current-free extrapolations with the photospheric magnetograms taken by Helioseismic and Magnetic Imager(HMI) on board the Solar Dynamics Observatory(SDO) spacecraft.In our analysis,we identified the coronal loop structures and construct two-dimensional maps of the corresponding magnetic field intensity in the plane of the sky(POS) above the limb.We derive the correlation coefficients between the coronal brightness and the magnetic field intensity for different heights of coronal layers.We further use a linear combination of a Gaussian and a quadratic profile to fit the correlation coefficients distribution,finding a largest correlation coefficient of 0.82 near 1.1 R(solar radii) where is almost the top of the closed loop system.For the small closed loop system identified,the correlation coefficient distributions crossing and covering the loop are calculated.We also investigate the correlation with extended heliocentric latitude zones and long period of one whole Carrington Rotation,finding again that the maximum correlation coefficient occurs at the same height.It is the first time for us to find that the correlation coefficients are high(all are larger than 0.8) at the loop-tops and showing poor correlation coefficients with some fluctuations near the feet of the coronal loops.Our findings indicate that,for the heating of the low-latitude closed loops,both DC(dissipation of currents) and AC(dissipation of Alfvén and magnetosonic waves) mechanisms should act展开更多
We have analyzed the solar irradiance data from the Earth Radiation Budget Satellite （ERBS） during the time period from 1984 October 15 to 2003 October 15.By first filtering the data by Simple Exponential Smoothing,...We have analyzed the solar irradiance data from the Earth Radiation Budget Satellite （ERBS） during the time period from 1984 October 15 to 2003 October 15.By first filtering the data by Simple Exponential Smoothing,we have applied the periodogram method to the processed data in order to search for its time variation.The study exhibits multi-periodicities on these data around 110,118,574 and 740d with very high confidence levels （more than 99%）.These periods are significantly similar to the periods of other solar activities which may suggest that solar irradiance may be associated with other solar activities.展开更多
The Solar Flare Index is regarded as one of the most important solar indices in the field of solarterrestrial research. It has the maximum effect on Earth of all other solar activity indices and is being considered fo...The Solar Flare Index is regarded as one of the most important solar indices in the field of solarterrestrial research. It has the maximum effect on Earth of all other solar activity indices and is being considered for describing the short-lived dynamo action inside the Sun. This paper attempts to study the short as well as long-term temporal fluctuations in the chromosphere region of the Sun using the Solar Flare Index. The daily Solar Flare Index for Northern, Southern Hemisphere and Total Disk are considered for a period from January 1976 to December 2014(total 14 245 days) for chaotic as well as periodic analysis.The 0–1 test has been employed to investigate the chaotic behavior associated with the Solar Flare Index.This test revealed that the time series data is non-linear and multi-periodic in nature with deterministic chaotic features. For periodic analysis, the Raleigh Power Spectrum algorithm has been used for identifying the predominant periods within the data along with their confidence score. The well-known fundamental period of 27 days and 11 years along with their harmonics are well affirmed in our investigation with a period of 28 days and 10.77 years. The presence of 14 days and 7 days periods in this investigation states the short-lived action inside the Sun. Our investigation also demonstrates the presence of other mid-range periods including the famous Rieger type period which are very much confirming the results obtained by other authors using various solar activity indicators.展开更多
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
To address the problem of the low accuracy of transverse velocity field measurements for small targets in highresolution solar images,we proposed a novel velocity field measurement method for high-resolution solar ima...To address the problem of the low accuracy of transverse velocity field measurements for small targets in highresolution solar images,we proposed a novel velocity field measurement method for high-resolution solar images based on PWCNet.This method transforms the transverse velocity field measurements into an optical flow field prediction problem.We evaluated the performance of the proposed method using the Hαand TiO data sets obtained from New Vacuum Solar Telescope observations.The experimental results show that our method effectively predicts the optical flow of small targets in images compared with several typical machine-and deeplearning methods.On the Hαdata set,the proposed method improves the image structure similarity from 0.9182 to0.9587 and reduces the mean of residuals from 24.9931 to 15.2818;on the TiO data set,the proposed method improves the image structure similarity from 0.9289 to 0.9628 and reduces the mean of residuals from 25.9908 to17.0194.The optical flow predicted using the proposed method can provide accurate data for the atmospheric motion information of solar images.The code implementing the proposed method is available on https://github.com/lygmsy123/transverse-velocity-field-measurement.展开更多
Observations of the sky irradiation intensity in the visible wavelengths during a solar eclipse permit to model the Sun diameter,a key number to constrain the internal structure of our star.In this paper,we present an...Observations of the sky irradiation intensity in the visible wavelengths during a solar eclipse permit to model the Sun diameter,a key number to constrain the internal structure of our star.In this paper,we present an algorithm that takes advantage of the precise Moon topography from Lunar Reconnaissance Orbiter to compute,with a high resolution in time,the geometrical part(i.e.top-of-atmosphere,and for a given wavelength)of the sky irradiation at any given location on the Earth during these events.The algorithm is also able to model the Baily’s beads.We give as an application the theoretical computation of the light curve corresponding to the solar eclipse observed at Lakeland(Queensland,North Australia)on 2012 November 13.The application to real data,with the introduction of atmospheric and instrumental passbands,will be considered in a forthcoming paper.展开更多
基金supported by the National Natural Science Foundation of China under grants 11873090, 12173086, 11873092, U2031148the CAS “Light of West China” Program。
文摘Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the higher coronal magnetic field intensity may correspond to.To try to further reveal the relationship between coronal green line brightness and magnetic field intensity,we use the 2 D coronal images observed by Yunnan Observatories Greenline Imaging System(YOGIS) of the 10 cm Lijiang coronagraph and the coronal magnetic field maps calculated from the current-free extrapolations with the photospheric magnetograms taken by Helioseismic and Magnetic Imager(HMI) on board the Solar Dynamics Observatory(SDO) spacecraft.In our analysis,we identified the coronal loop structures and construct two-dimensional maps of the corresponding magnetic field intensity in the plane of the sky(POS) above the limb.We derive the correlation coefficients between the coronal brightness and the magnetic field intensity for different heights of coronal layers.We further use a linear combination of a Gaussian and a quadratic profile to fit the correlation coefficients distribution,finding a largest correlation coefficient of 0.82 near 1.1 R(solar radii) where is almost the top of the closed loop system.For the small closed loop system identified,the correlation coefficient distributions crossing and covering the loop are calculated.We also investigate the correlation with extended heliocentric latitude zones and long period of one whole Carrington Rotation,finding again that the maximum correlation coefficient occurs at the same height.It is the first time for us to find that the correlation coefficients are high(all are larger than 0.8) at the loop-tops and showing poor correlation coefficients with some fluctuations near the feet of the coronal loops.Our findings indicate that,for the heating of the low-latitude closed loops,both DC(dissipation of currents) and AC(dissipation of Alfvén and magnetosonic waves) mechanisms should act
文摘We have analyzed the solar irradiance data from the Earth Radiation Budget Satellite （ERBS） during the time period from 1984 October 15 to 2003 October 15.By first filtering the data by Simple Exponential Smoothing,we have applied the periodogram method to the processed data in order to search for its time variation.The study exhibits multi-periodicities on these data around 110,118,574 and 740d with very high confidence levels （more than 99%）.These periods are significantly similar to the periods of other solar activities which may suggest that solar irradiance may be associated with other solar activities.
基金the support extended by Jadavpur UniversityWest Bengal India. This work is a part of RUSA 2.0 Faculty Major Research Project under Jadavpur University。
文摘The Solar Flare Index is regarded as one of the most important solar indices in the field of solarterrestrial research. It has the maximum effect on Earth of all other solar activity indices and is being considered for describing the short-lived dynamo action inside the Sun. This paper attempts to study the short as well as long-term temporal fluctuations in the chromosphere region of the Sun using the Solar Flare Index. The daily Solar Flare Index for Northern, Southern Hemisphere and Total Disk are considered for a period from January 1976 to December 2014(total 14 245 days) for chaotic as well as periodic analysis.The 0–1 test has been employed to investigate the chaotic behavior associated with the Solar Flare Index.This test revealed that the time series data is non-linear and multi-periodic in nature with deterministic chaotic features. For periodic analysis, the Raleigh Power Spectrum algorithm has been used for identifying the predominant periods within the data along with their confidence score. The well-known fundamental period of 27 days and 11 years along with their harmonics are well affirmed in our investigation with a period of 28 days and 10.77 years. The presence of 14 days and 7 days periods in this investigation states the short-lived action inside the Sun. Our investigation also demonstrates the presence of other mid-range periods including the famous Rieger type period which are very much confirming the results obtained by other authors using various solar activity indicators.
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 under Grant Nos.12063002,12163004,and 12073077。
文摘To address the problem of the low accuracy of transverse velocity field measurements for small targets in highresolution solar images,we proposed a novel velocity field measurement method for high-resolution solar images based on PWCNet.This method transforms the transverse velocity field measurements into an optical flow field prediction problem.We evaluated the performance of the proposed method using the Hαand TiO data sets obtained from New Vacuum Solar Telescope observations.The experimental results show that our method effectively predicts the optical flow of small targets in images compared with several typical machine-and deeplearning methods.On the Hαdata set,the proposed method improves the image structure similarity from 0.9182 to0.9587 and reduces the mean of residuals from 24.9931 to 15.2818;on the TiO data set,the proposed method improves the image structure similarity from 0.9289 to 0.9628 and reduces the mean of residuals from 25.9908 to17.0194.The optical flow predicted using the proposed method can provide accurate data for the atmospheric motion information of solar images.The code implementing the proposed method is available on https://github.com/lygmsy123/transverse-velocity-field-measurement.
基金the National Natural Science Foundation of China(U1831132 and 41804025)grant of Hubei Province Natural Science(2018CFA087)+2 种基金supported by the grant from Key Laboratory of Lunar and Deep Space Exploration,CASLIESMARS Special Research Fundingfunded through a DAR grant in planetology from the French Space Agency(CNES)。
文摘Observations of the sky irradiation intensity in the visible wavelengths during a solar eclipse permit to model the Sun diameter,a key number to constrain the internal structure of our star.In this paper,we present an algorithm that takes advantage of the precise Moon topography from Lunar Reconnaissance Orbiter to compute,with a high resolution in time,the geometrical part(i.e.top-of-atmosphere,and for a given wavelength)of the sky irradiation at any given location on the Earth during these events.The algorithm is also able to model the Baily’s beads.We give as an application the theoretical computation of the light curve corresponding to the solar eclipse observed at Lakeland(Queensland,North Australia)on 2012 November 13.The application to real data,with the introduction of atmospheric and instrumental passbands,will be considered in a forthcoming paper.
