In the solar atmosphere, there exist two frequently-observed phenomena, Moreton waves and EIT(extreme-ultraviolet imaging telescope) waves, whose physical nature is still under debate. In this work, we perform a three...In the solar atmosphere, there exist two frequently-observed phenomena, Moreton waves and EIT(extreme-ultraviolet imaging telescope) waves, whose physical nature is still under debate. In this work, we perform a three-dimensional ray-tracing simulation for the propagation of fast magnetoacoustic waves. We build a stratified solar atmosphere model and take partial ionization into consideration to give an exact description of chromosphere and transition region. The calculated result is compared with a flare event observation in which both Moreton waves and EIT waves were present. In agreement with observations, the calculated wavefront show different kinematical characteristics in different propagation directions during different times.Moreton waves and EIT waves have higher propagation speeds near the active region where the magnetic field strength is strong. The result suggests that both Moreton waves and EIT waves of this event can be interpreted as the fast magnetoacoustic waves propagating at different heights in the solar atmosphere.展开更多
To simultaneously obtain high-resolution multi-wavelength （from visible to near infrared） tomographic images of the solar atmosphere, a high-performance multi-wavelength optical filter has to be used in solar imagin...To simultaneously obtain high-resolution multi-wavelength （from visible to near infrared） tomographic images of the solar atmosphere, a high-performance multi-wavelength optical filter has to be used in solar imaging telescopes. In this Letter, the fabrication of the multi-wavelength filter for solar tomographic imaging is described in detail. For this filter, Ta2O5 and SiO2 are used as high- and low-index materials, respectively, and the multilayer structure is optimized by commercial Optilayer software at a 7.5° angle of incidence. Experimentally, this multi-wavelength optical filter is prepared by a plasma ion-assisted deposition technique with optimized deposition parameters. High transmittance at 393.3, 396.8, 430.5, 525, 532.4, 656.8, 705.8, 854.2, 1083, and 1565.3 nm, as well as high reflectance at 500 and 589 nm are achieved. Excellent environmental durability, demonstrated via temperature and humidity tests, is also established.展开更多
Adaptive optics （AO）, which provides diffraction limited imaging over a field-of-view （FOV）, is a powerful technique for solar observation. In the tomographic approach, each wavefront sensor （WFS） is looking at ...Adaptive optics （AO）, which provides diffraction limited imaging over a field-of-view （FOV）, is a powerful technique for solar observation. In the tomographic approach, each wavefront sensor （WFS） is looking at a single reference that acts as a guide star. This allows a 3D reconstruction of the distorted wavefront to be made. The correction is applied by one or more deformable mirrors （DMs）. This technique benefits from information about atmospheric turbulence at different layers, which can be used to reconstruct the wavefront extremely well. With the assistance of the MAOS software package, we consider the tomography errors and WFS aliasing errors, and focus on how the performance of a solar telescope （pointing toward zenith） is related to atmospheric anisoplanatism. We theoretically quantify the performance of the to- mographic solar AO system. The results indicate that the tomographic AO system can improve the average Strehl ratio of a solar telescope in a 10＂ - 80＂ diameter FOV by only employing one DM conjugated to the telescope pupil. Furthermore, we discuss the effects of DM conjugate altitude on the correction achievable by the AO system by selecting two atmospheric models that differ mainly in terms of atmospheric prop- erties at ground level, and present the optimum DM conjugate altitudes for different observation sites.展开更多
In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in sur...In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in surface albedo, sin-gle scattering albedo, asymmetrical factor of scattering phase function, instrumental constant and the approximate expression of diffusion flux is analy/ed, and then a method for determining surface albedo in shorter wavelength range is presented.展开更多
Ellerman bombs(EBs)and ultraviolet(UV)bursts are common brightening phenomena,which are usually generated in the low solar atmosphere of emerging flux regions.In this paper,we have investigated the emergence of an ini...Ellerman bombs(EBs)and ultraviolet(UV)bursts are common brightening phenomena,which are usually generated in the low solar atmosphere of emerging flux regions.In this paper,we have investigated the emergence of an initial un-twisted magnetic flux rope based on three-dimensional(3 D)magneto-hydrodynamic(MHD)simulations.The EB-like and UV burst-like activities successively appear in the U-shaped part of the undulating magnetic fields triggered by the Parker instability.The EB-like activity starts to appear earlier and lasts for about 80 seconds.Six minutes later,a much hotter UV burstlike event starts to appear and lasts for about 60 seconds.Along the direction vertical to the solar surface,both the EB and UV burst start in the low chromosphere,but the UV burst extends to a higher altitude in the up chromosphere.The regions with apparent temperature increase in the EB and UV burst are both located inside the small twisted flux ropes generated in magnetic reconnection processes,which are consistent with the previous 2 D simulations that most hot regions are usually located inside the magnetic islands.However,the twisted flux rope corresponding to the EB is only strongly heated after it floats up to an altitude much higher than the reconnection site during that period.Our analyses show that the EB is heated by the shocks driven by the strong horizontal flows at two sides of the U-shaped magnetic fields.The twisted flux rope corresponding to the UV burst is heated by the driven magnetic reconnection process.展开更多
The two-stream approximation is applied to solve the multiple scattered radiation transfer equations for an inhomogeneous aerosol atmosphere.The accurate absorption of water vapor,ozone,carbon dioxide and molecular ox...The two-stream approximation is applied to solve the multiple scattered radiation transfer equations for an inhomogeneous aerosol atmosphere.The accurate absorption of water vapor,ozone,carbon dioxide and molecular oxygen is calculated.Calculations have been carried out band by band for the beating rate of atmosphere.The results show that the effect of aerosols on solar heating of the atmosphere is significant.展开更多
We present a model for simulating wave propagation in stratified magnetoatmospheres. The model is based on equations of ideal MHD together with gravitational source terms. In addition, we present suitable boundary dat...We present a model for simulating wave propagation in stratified magnetoatmospheres. The model is based on equations of ideal MHD together with gravitational source terms. In addition, we present suitable boundary data and steady statesto model wave propagation. A finite volume framework is developed to simulate thewaves. The framework is based on HLL and Roe type approximate Riemann solversfor numerical fluxes, a positivity preserving fractional steps method for discretizingthe source and modified characteristic and Neumann type numerical boundary conditions. Second-order spatial and temporal accuracy is obtained by using an ENO piecewise linear reconstruction and a stability preserving Runge-Kutta method respectively.The boundary closures are suitably modified to ensure mass balance. The numericalframework is tested on a variety of test problems both for hydrodynamic as well asmagnetohydrodynamic configurations. It is observed that only suitable choices of HLLsolvers for the numerical fluxes and balanced Neumann type boundary closures yieldstable results for numerical wave propagation in the presence of complex magneticfields.展开更多
基金the National Natural Science Foundation of China(Grant Nos.41274174,41422405,41274169&41421063)the Fundamental Research Funds for the Central Universities(Grant No.WK2080000077)
文摘In the solar atmosphere, there exist two frequently-observed phenomena, Moreton waves and EIT(extreme-ultraviolet imaging telescope) waves, whose physical nature is still under debate. In this work, we perform a three-dimensional ray-tracing simulation for the propagation of fast magnetoacoustic waves. We build a stratified solar atmosphere model and take partial ionization into consideration to give an exact description of chromosphere and transition region. The calculated result is compared with a flare event observation in which both Moreton waves and EIT waves were present. In agreement with observations, the calculated wavefront show different kinematical characteristics in different propagation directions during different times.Moreton waves and EIT waves have higher propagation speeds near the active region where the magnetic field strength is strong. The result suggests that both Moreton waves and EIT waves of this event can be interpreted as the fast magnetoacoustic waves propagating at different heights in the solar atmosphere.
基金partially supported by the West Light Foundation of the Chinese Academy of Sciences
文摘To simultaneously obtain high-resolution multi-wavelength （from visible to near infrared） tomographic images of the solar atmosphere, a high-performance multi-wavelength optical filter has to be used in solar imaging telescopes. In this Letter, the fabrication of the multi-wavelength filter for solar tomographic imaging is described in detail. For this filter, Ta2O5 and SiO2 are used as high- and low-index materials, respectively, and the multilayer structure is optimized by commercial Optilayer software at a 7.5° angle of incidence. Experimentally, this multi-wavelength optical filter is prepared by a plasma ion-assisted deposition technique with optimized deposition parameters. High transmittance at 393.3, 396.8, 430.5, 525, 532.4, 656.8, 705.8, 854.2, 1083, and 1565.3 nm, as well as high reflectance at 500 and 589 nm are achieved. Excellent environmental durability, demonstrated via temperature and humidity tests, is also established.
基金The China Scholarship Council Foundation is acknowledged for funding this research
文摘Adaptive optics （AO）, which provides diffraction limited imaging over a field-of-view （FOV）, is a powerful technique for solar observation. In the tomographic approach, each wavefront sensor （WFS） is looking at a single reference that acts as a guide star. This allows a 3D reconstruction of the distorted wavefront to be made. The correction is applied by one or more deformable mirrors （DMs）. This technique benefits from information about atmospheric turbulence at different layers, which can be used to reconstruct the wavefront extremely well. With the assistance of the MAOS software package, we consider the tomography errors and WFS aliasing errors, and focus on how the performance of a solar telescope （pointing toward zenith） is related to atmospheric anisoplanatism. We theoretically quantify the performance of the to- mographic solar AO system. The results indicate that the tomographic AO system can improve the average Strehl ratio of a solar telescope in a 10＂ - 80＂ diameter FOV by only employing one DM conjugated to the telescope pupil. Furthermore, we discuss the effects of DM conjugate altitude on the correction achievable by the AO system by selecting two atmospheric models that differ mainly in terms of atmospheric prop- erties at ground level, and present the optimum DM conjugate altitudes for different observation sites.
文摘In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in surface albedo, sin-gle scattering albedo, asymmetrical factor of scattering phase function, instrumental constant and the approximate expression of diffusion flux is analy/ed, and then a method for determining surface albedo in shorter wavelength range is presented.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11973083 and 11933009)the Strategic Priority Research Program of CAS(Grant Nos.XDA17040507 and QYZDJ-SSWSLH012)+7 种基金the grants associated with the Yunling Scholar Project of the Yunnan Province and the Yunnan Province Scientist Workshop of Solar Physicsthe Youth Innovation Promotion Association CAS 2017the Applied Basic Research of Yunnan Province in China(Grant 2018FB009)the Yunnan Ten-Thousand Talents Plan-Young top talentsthe project of the Group for Innovation of Yunnan Province(Grant 2018HC023)the Yunnan Ten-Thousand Talents Plan-Yunling Scholar Projectthe Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(NSFC015-460,NSFC2015-463,the second phase)Computational Solar Physics Laboratory of Yunnan Observatories,the key Laboratory of Solar Activity(Grant KLSA202103)。
文摘Ellerman bombs(EBs)and ultraviolet(UV)bursts are common brightening phenomena,which are usually generated in the low solar atmosphere of emerging flux regions.In this paper,we have investigated the emergence of an initial un-twisted magnetic flux rope based on three-dimensional(3 D)magneto-hydrodynamic(MHD)simulations.The EB-like and UV burst-like activities successively appear in the U-shaped part of the undulating magnetic fields triggered by the Parker instability.The EB-like activity starts to appear earlier and lasts for about 80 seconds.Six minutes later,a much hotter UV burstlike event starts to appear and lasts for about 60 seconds.Along the direction vertical to the solar surface,both the EB and UV burst start in the low chromosphere,but the UV burst extends to a higher altitude in the up chromosphere.The regions with apparent temperature increase in the EB and UV burst are both located inside the small twisted flux ropes generated in magnetic reconnection processes,which are consistent with the previous 2 D simulations that most hot regions are usually located inside the magnetic islands.However,the twisted flux rope corresponding to the EB is only strongly heated after it floats up to an altitude much higher than the reconnection site during that period.Our analyses show that the EB is heated by the shocks driven by the strong horizontal flows at two sides of the U-shaped magnetic fields.The twisted flux rope corresponding to the UV burst is heated by the driven magnetic reconnection process.
文摘The two-stream approximation is applied to solve the multiple scattered radiation transfer equations for an inhomogeneous aerosol atmosphere.The accurate absorption of water vapor,ozone,carbon dioxide and molecular oxygen is calculated.Calculations have been carried out band by band for the beating rate of atmosphere.The results show that the effect of aerosols on solar heating of the atmosphere is significant.
文摘We present a model for simulating wave propagation in stratified magnetoatmospheres. The model is based on equations of ideal MHD together with gravitational source terms. In addition, we present suitable boundary data and steady statesto model wave propagation. A finite volume framework is developed to simulate thewaves. The framework is based on HLL and Roe type approximate Riemann solversfor numerical fluxes, a positivity preserving fractional steps method for discretizingthe source and modified characteristic and Neumann type numerical boundary conditions. Second-order spatial and temporal accuracy is obtained by using an ENO piecewise linear reconstruction and a stability preserving Runge-Kutta method respectively.The boundary closures are suitably modified to ensure mass balance. The numericalframework is tested on a variety of test problems both for hydrodynamic as well asmagnetohydrodynamic configurations. It is observed that only suitable choices of HLLsolvers for the numerical fluxes and balanced Neumann type boundary closures yieldstable results for numerical wave propagation in the presence of complex magneticfields.
