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The Chinese Hα Solar Explorer(CHASE) mission: An overview

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Science China(Physics,Mechanics & Astronomy) 2022年第8期65卷 2-9页

作者： Chuan Li Cheng Fang Zhen Li MingDe Ding PengFei Chen Ye Qiu Wei You Yuan Yuan MinJie An HongJiang Tao XianSheng Li Zhe Chen Qiang Liu Gui Mei Liang Yang Wei Zhang WeiQiang Cheng JianXin Chen ChangYa Chen Qiang Gu QingLong Huang MingXing Liu ChengShan Han HongWei Xin ChangZheng Chen YiWei Ni WenBo Wang ShiHao Rao HaiTang Li Xi Lu Wei Wang Jun Lin YiXian Jiang LingJie Meng Jian Zhao School of Astronomy and Space Science Nanjing University Key Laboratory for Modern Astronomy and Astrophysics (Nanjing University) Ministry of Education Shanghai Institute of Satellite Engineering Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Shanghai Academy of Spaceflight Technology China Center for Resources Satellite Data and Application China Aerospace Science and Technology Corporation Key and Special Project Center of China National Space Administration (CNSA)

The Chinese Hα Solar Explorer(CHASE), dubbed “Xihe”—Goddess of the Sun, was launched on October 14, 2021 as the first solar space mission of China National Space Administration(CNSA). The CHASE mission is designed to test a newly developed satellite platform and to acquire the spectroscopic observations in the Hα waveband. The Hα Imaging Spectrograph(HIS)is the scientific payload of the CHASE satellite. It consists of two observational modes: raster scanning mode and continuum imaging mode. The raster scanning mode obtains full-Sun or region-of-interest spectral images from 6559.7 to 6565.9 ? and from 6567.8 to 6570.6 ? with 0.024 ? pixel spectral resolution and 1 min temporal resolution. The continuum imaging mode obtains photospheric images in continuum around 6689 ? with the full width at half maximum of 13.4 ?. The CHASE mission will advance our understanding of the dynamics of solar activity in the photosphere and chromosphere. In this paper, we present an overview of the CHASE mission including the scientific objectives, HIS instrument overview, data calibration flow, and first results of on-orbit observations.

关键词： space-based telescope solar physics chromosphere photosphere

Magnetohydrostatic modeling of the solar atmosphere

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Science China(Technological Sciences) 2022年第8期65卷 1710-1726页

作者： ZHU XiaoShuai NEUKIRCH Thomas WIEGELMANN Thomas State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Mathematics and Statistics University of St AndrewsSt Andrews KY169SSUK Max-Planck-Institut f¨ur Sonnensystemforschung G¨ottingen 37077Germany

Understanding structures and evolutions of the magnetic fields and plasma in multiple layers on the Sun is very important. A force-free magnetic field which is an accurate approximation of the solar corona due to the low plasma β has been widely studied and used to model the coronal magnetic structure. While the force-freeness assumption is well satisfied in the solar corona, the lower atmosphere is not force-free given the high plasma β. Therefore, a magnetohydrostatic(MHS) equilibrium which takes into account plasma forces, such as pressure gradient and gravitational force, is considered to be more appropriate to describe the lower atmosphere. This paper reviews both analytical and numerical extrapolation methods based on the MHS assumption for calculating the magnetic fields and plasma in the solar atmosphere from measured magnetograms.

关键词： magnetic field photosphere chromosphere corona

Calibration procedures for the CHASE/HIS science data

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Science China(Physics,Mechanics & Astronomy) 2022年第8期65卷 10-17页

作者： Ye Qiu ShiHao Rao Chuan Li Cheng Fang MingDe Ding Zhen Li YiWei Ni WenBo Wang Jie Hong Qi Hao Yu Dai PengFei Chen XiaoSheng Wan Zhi Xu Wei You Yuan Yuan HongJiang Tao XianSheng Li YuKun He Qiang Liu School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Key Laboratory for Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Shanghai Institute of Satellite Engineering Shanghai 201109China Changchun Institute of Optics Fine Mechanics and PhysicsUniversity of Chinese Academy of SciencesChangchun 130033China

The Hα line is an important optical line in solar observations containing the information from the photosphere to the chromosphere. To study the mechanisms of solar eruptions and the plasma dynamics in the lower atmosphere, the Chinese Hα Solar Explorer(CHASE) was launched into a Sun-synchronous orbit on October 14, 2021. The scientific payload of the CHASE satellite is the Hα Imaging Spectrograph(HIS). The CHASE/HIS acquires, for the first time, seeing-free Hα spectroscopic observations with high spectral and temporal resolutions. It consists of two observational modes. The raster scanning mode provides full-Sun or region-of-interest spectra at Hα(6559.7-6565.9 ?) and Fe I(6567.8-6570.6 ?) wavebands. The continuum imaging mode obtains full-Sun photospheric images at around 6689 ?. In this paper, we present detailed calibration procedures for the CHASE/HIS science data, including the dark-field and flat-field correction, slit image curvature correction, wavelength and intensity calibration, and coordinate transformation. The higher-level data products can be directly used for scientific research.

关键词： space-based telescope solar physics chromosphere photosphere

THE TANGENTIAL DISCONTINUOUS SURFACE OF VELOCITY IN SOLAR chromosphere

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Science China Mathematics 1991年第11期34卷 1354-1364页

作者：胡文瑞张洪起陈济民 Institute of Mechanics Academia Sinica Beijing 100080 PRC Beijing Observatory Academia Sinica Beijing 100080 PRC

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.

关键词： solar chromosphere magnetic field velocity field.

Image Desaturation for SDO/AIA Using Mixed Convolution Network

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Research in Astronomy and Astrophysics 2022年第6期22卷 91-100页

作者： Xuexin Yu Long Xu Zhixiang Ren Dong Zhao Wenqing Sun National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Peng Cheng National Laboratory Shenzhen 518000China National Space Science Center Chinese Academy of SciencesBeijing 100190China State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and EngineeringBeihang UniversityBeijing 100190China

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.

关键词： Sun:activity Sun atmosphere-Sun chromosphere

Analysis of sudden variations in photospheric magnetic fields during a large flare and their influences in the solar atmosphere

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Research in Astronomy and Astrophysics 2016年第8期16卷 95-112页

作者： Brajesh Kumar Ankala Raja Bayanna Parameswaran Venkatakrishnan Shibu Kuchandy Mathew Udaipur Solar Observatory Physical Research Laboratory Dewali Badi Road Udaipur 313004 Rajasthan India Indian Institute of Astrophysics Ⅱ Block Koramangala Bangalore 560034 India

The solar active region NOAA 11719 produced a large two-ribbon flare on 2013 April 11. We have investigated sudden variations in the photospheric magnetic fields in this active region during the flare by employing magnetograms obtained in the spectral line Fe I 6173 A acquired by the Helioseismic and Magnetic Imager （HMI） onboard the Solar Dynamics Observatory （SDO） spacecraft. The analysis of the line-of-sight magnetograms from HMI show sudden and persistent magnetic field changes at different locations of the active region before the onset of the flare and during the flare. The vector magnetic field observations available from HMI also show coincident variations in the total magnetic field strength and its inclination angle at these locations. Using the simultaneous Dopplergrams obtained from HMI, we observe perturbations in the photospheric Doppler signals following the sudden changes in the magnetic fields in the aforementioned locations. The power spectrum analysis of these velocity signals shows enhanced acoustic power in these affected locations during the flare as compared to the pre-flare condition. Accompanying these observations, we have also used nearly simultaneous chromospheric observations obtained in the spectral line Ha 6562.8 A by the Global Oscillation Network Group （GONG） to study the evolution of flare- ribbons and intensity oscillations in this active region. The Ha intensity oscillations also show enhanced oscillatory power during the flare in the aforementioned locations. These results indicate that the transient Lorentz force associated with sudden changes in the magnetic fields could drive localized photospheric and chromospheric oscillations, like the flare-induced oscillations in the solar atmosphere.

关键词： Sun sunspots -- Sun flares -- Sun magnetic fields -- Sun oscillations -- Sun photosphere-- Sun chromosphere

Network and plage indices from Kodaikanal Ca-K data

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Research in Astronomy and Astrophysics 2014年第2期14卷 229-232页

作者： K.P.Raju Jagdev Singh Indian Institute of Astrophysics

The Ca II K filtergrams from Kodaikanal Solar Observatory have been used to study solar activity. The images are dominated by the chromospheric network and plages. Programs have been developed to obtain the network and plage indices from the daily images as functions of solar latitude and time. Preliminary results from the analysis are reported here. The network and plage indices were found to follow the sunspot cycle. A secondary peak is found during the period of declining activity in both the indices. A comparison of network indices from the northern and the southern hemispheres shows that the former is more active than the latter. However such an asymmetry is not clearly seen in the plage index.

关键词： Sun chromosphere

Solar ultraviolet bursts in a coordinated observation of IRIS,Hinode and SDO

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Science China(Technological Sciences) 2019年第9期62卷 1555-1564页

作者： CHEN YaJie TIAN Hui ZHU XiaoShuai SAMANTA Tanmoy WANG LingHua HE JianSen School of Earth and Space Sciences Peking UniversityBeijing 100871China Max Planck Institute for Solar System Research Gottingen 37077Germany

Solar ultraviolet(UV) bursts are small-scale compact brightenings in transition region images. The spectral profiles of transition region lines in these bursts are significantly enhanced and broadened, often with chromospheric absorption lines such as Ni ii 1335.203 and 1393.330 A superimposed. We investigate the properties of several UV bursts using a coordinated observation of the Interface Region Imaging Spectrograph(IRIS), Solar Dynamics Observatory(SDO), and Hinode on February 7, 2015. We have identified 12 UV bursts, and 11 of them reveal small blueshifts of the Ni ii absorption lines. However, the Ni ii lines in one UV burst exhibit obvious redshifts of ~20 km s^-1, which appear to be related to the cold plasma downflows observed in the IRIS slit-jaw images. We also examine the three-dimensional magnetic field topology using a magnetohydrostatic model, and find that some UV bursts are associated with magnetic null points or bald patches. In addition, we find that these UV bursts reveal no obvious coronal signatures from the observations of the Atmospheric Imaging Assembly(AIA) on board SDO and the EUV Imaging Spectrometer(EIS) on board Hinode.

关键词： Sun: chromosphere Sun: transition region Sun: UV radiation magnetic reconnection

Propagation of Fast Magnetoacoustic Waves in Stratified Solar Atmosphere

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Chinese Physics Letters 2006年第2期23卷 399-402页

作者：郑惠南张元元王水王传兵李毅 CAS Key Laboratory for Basic Plasma Physics School of Earth and Space Sciences University of Science and Technology of China Hefei 230026

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.

关键词： CORONAL MASS EJECTION MAGNETIC-FLUX MORETON WAVE H-ALPHA chromosphere EIT SIMULATIONS MODELS