太阳二维光谱观测研究的进展和展望

论述了太阳二维光谱观测和研究的重大意义，综述了二维光谱观测技术和仪器的进展，特别介绍了应用ＣＣＤ的成像光谱仪的最近发展。文中还介绍了近年来二维光谱观测研究所取得的一些新结果，展望了未来观测技术和课题研究的发展前景。     

南京大学太阳塔CCD成像光谱观测系统和初步观测结果

本文介绍南京大学太阳塔的ＣＣＤ成像光谱观测系统的结构，工作方式，给出了该系统的一些性能测试结果，作为应用该系统的实例，文中给出了根据该系统观测的二维光谱资料，经处理得到的一个Ｈａ耀斑在线心和不同偏带处单色像的变化过程，该耀斑的亮度场轮廓图和速度场轮廓图。     

云台凤凰山太阳光谱最佳观测时间讨论

将一年中可以进行光谱观测的时间相对最多，同时太阳成像质量相对较好的月份作为光谱观测最佳时间。为此我们统计了光谱仪1976年到1987年的观测资料，初步分析得出云台凤凰山太阳光谱最佳观测时间的年分布情况，相对好一些的是9月份，其次是3～4月份。     

红外波段太阳观测技术方法研究

1m红外太阳塔是我国未来重点发展的地面太阳观测设备，本文的所有工作均围绕着与此相关的红外波段太阳观测技术方法展开。1．针对望远镜实验平台－云台太阳光谱仪，建立了光谱仪分光流量,工用多种实验手段验证了其可靠性。利用该模型计算了Fe Ⅰ1.56μm红外太阳光 谱的分光流量，分析了实验观测的可行性及改进方案。2．针对探测器实验平台－PtSi红外焦平面阵列相机，建立了FeⅠ1.56μm光谱观测信噪比模型，模拟了各种噪声对观测的影响。在此基础上，在国内首次成功进行了FeⅠ1.56μm红外太阳光谱的面阵观测实验。3．在红外观测实验所处的高背景低对比度条件下，讨论了红外太阳光谱观测的图像处理方法，分析了观测中出现的干涉条纹的来源及解决办法，初步建立起了一整套红外太阳光谱与成像的定标方法和图像处理方法。4．首次利用PVA材料，设计研制了一套FeⅠ1.56μm近红外Stokes参量偏振仪，并将该偏振仪安装在美国国立天文台McMath望远镜上进行了观测实验。针对一太阳黑子，通过扫描进行了二维的Stokes参量观测。同时建立了一套从Stokes参量反演磁矢量场的方法，并将反演的结果与怀柔太阳磁场望远镜的观测结果进行了比对。5．针对1m红外太阳塔的太阳光谱仪系统，给出了垂直多波段光谱仪和红外大色散光谱仪的光、机初步设计。6．针对1m红外太阳塔的科学目标，提出了多波段光谱仪探测器系统方案，对红外大色散光谱仪所使用的红外探测器也进行了初步方案设计。     

NVST垂直双光谱切换扫描系统

1 m新真空太阳望远镜(New Vacuum Solar Telescope, NVST)的科学目标之一是对太阳活动区域进行二维光谱扫描观测。基于1 m新真空太阳望远镜多波段光谱仪(Multi-Band Spectrometer, MBS)和大色散光谱仪(High Dispersion Spectrometer, HDS)提出了垂直双光谱切换扫描系统,可实现相互垂直的两个光谱仪的光谱扫描观测任务,并实现两个光谱仪之间的切换。分析了光谱扫描观测的原理和过程,结合终端仪器系统的具体构造,完成了扫描系统的光机结构设计和装调分析,并对扫描系统进行了性能测试,包括系统稳定性、扫描直线度以及扫描步幅精度。测试结果满足预期功能需求和精度要求,为后续1 m新真空太阳望远镜进行常规光谱扫描观测提供了支持。     

太阳活动区磁场观测的一种新方法

在太阳活动区的物理研究中,特别是在二维动力学光谱分析中,迫切需要相应活动区的磁图资料。本文介绍了在太阳光谱仪的入射狭缝后安装一种新型偏振器进行活动区二维磁场观测的新方法。这种方法不仅能获得日面上任一点的磁场强度,且可快速获得活动区的纵向场磁图。除此之外,还可利用多条谱线的同时观测,获得有关磁力线管结构等方面的资料。     

1989年8月17日耀斑环的视向速度场

多云模型’’是处理太阳活动体光谱不对称轮廓的有效方法,本文给出了该方法的一个具体应用实例,利用云南天文台二维多波段太阳光谱仪观测的１９８９年８月１７日耀斑环Ｈβ波段光谱资料,得到了该耀斑环的视向速度场．     

云台凤凰山太阳光谱最佳观测时间讨论

将一年中可以进行光谱观测的时间相对最多,同时太阳成像质量相对较好的月份作为光谱观测最佳时间。为此我们统计了光谱仪1976年到1987年的观测资料,初步分析得出云台凤凰山太阳光谱最佳观测时间的年分布情况,相对好一些的是9月份,其次是3～4月份。     

红外波段太阳观测技术方法研究

1m红外太阳塔是我国未来重点发展的地面太阳观测设备 ,本文的所有工作均围绕着与此相关的红外波段太阳观测技术方法展开。1 .针对望远镜实验平台—云台太阳光谱仪 ,建立了光谱仪分光流量模型 ,并用多种实验手段验证了其可靠性。利用该模型计算了FeⅠ 1 .56μm红外太阳光谱的分光流量 ,分析了实验观测的可行性及改进方案。2 .针对探测器实验平台—PtSi红外焦平面阵列相机 ,建立了FeⅠ 1 .56μm光谱观测信噪比模型 ,模拟了各种噪声对观测的影响。在此基础上 ,在国内首次成功进行了FeⅠ1 .56μm红外太阳光谱的面阵观测实验。3 .在红外观测实验所处的高背景低对比度条件下 ,讨论了红外太阳光谱观测的图像处理方法 ,分析了观测中出现的干涉条纹的来源及解决办法 ,初步建立起了一整套红外太阳光谱与成像的定标方法和图像处理方法。4 .首次利用PVA材料 ,设计研制了一套FeⅠ 1 .56μm近红外Stokes参量偏振仪 ,并将该偏振仪安装在美国国立天文台McMath望远镜上进行了观测实验。针对一太阳黑子 ,通过扫描进行了二维的Stokes参量观测。同时建立了一套从Stokes参量反演磁矢量场的方法 ,并将反演的结果与怀柔太阳磁场望远镜的观测结果进行了比对。5.针对 1m红外太阳塔的太阳光谱仪系统 ,给出了垂直多波段光谱仪和红外     

1989年8月17日太阳边缘耀斑和速度场研究

本文云南天文台二维光谱仪观测的１９８９年８月１７日耀斑的Ｈβ波 段光谱资料，采用多云模型的方法，得到此耀斑的观测视向速度分布，并在一定的简化和假设下，采用ＭＨＤ理论计算了几种情况下光耀斑环内物质运动的视向速度分布，与观测的视向速度分布加以比较，研究和探讨耀斑环中的物质运动情况。     

Low‐frequency heliographic observations of the quiet Sun corona

We present new results of heliographic observations of quiet‐Sun radio emission fulfilled by the UTR‐2 radio telescope. The solar corona investigations have been made close to the last solar minimum (Cycle 23) in the late August and early September of 2010 by means of the two‐dimensional heliograph within 16.5–33 MHz. Moreover, the UTR‐2 radio telescope was used also as an 1‐D heliograph for one‐dimensional scanning of the Sun at the beginning of September 2010 as well as in short‐time observational campaigns in April and August of 2012. The average values of integral flux density of the undisturbed Sun continuum emission at different frequencies have been found. Using the data, we have determined the spectral index of quiet‐Sun radio emission in the range 16.5–200 MHz. It is equal to –2.1±0.1. The brightness distribution maps of outer solar corona at frequencies 20.0 MHz and 26.0 MHz have been obtained. The angular sizes of radio Sun were estimated. It is found that the solar corona at these frequencies is stretched‐out along equatorial direction. The coefficient of corona ellipticity varies slightly during above period. Its mean magnitudes are equal to ≈ 0.75 and ≈ 0.73 at 20.0 MHz and 26.0 MHz, respectively. The presented results for continuum emission of solar corona conform with being ones at higher frequencies. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High‐fidelity spectroscopy at the highest resolutions

High‐fidelity spectroscopy presents challenges for both observations and in designing instruments. High‐resolution and high‐accuracy spectra are required for verifying hydrodynamic stellar atmospheres and for resolving intergalactic absorption‐line structures in quasars. Even with great photon fluxes from large telescopes with matching spectrometers, precise measurements of line profiles and wavelength positions encounter various physical, observational, and instrumental limits. The analysis may be limited by astrophysical and telluric blends, lack of suitable lines, imprecise laboratory wavelengths, or instrumental imperfections. To some extent, such limits can be pushed by forming averages over many similar spectral lines, thus averaging away small random blends and wavelength errors. In situations where theoretical predictions of lineshapes and shifts can be accurately made (e.g., hydrodynamic models of solar‐type stars), the consistency between noisy observations and theoretical predictions may be verified; however this is not feasible for, e.g., the complex of intergalactic metal lines in spectra of distant quasars, where the primary data must come from observations. To more fully resolve lineshapes and interpret wavelength shifts in stars and quasars alike, spectral resolutions on order R = 300 000 or more are required; a level that is becoming (but is not yet) available. A grand challenge remains to design efficient spectrometers with resolutions approaching R = 1 000 000 for the forthcoming generation of extremely large telescopes (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

银河系化学元素的丰度特征和合成图像(I):星际介质中轻元素丰度的观测及其特征

给出并解释了星际介质中轻元素D，3He，4He和Li的最新观测数据．星际介质中轻元素的丰度观测结果可以用来检验标准大爆炸核合成理论，因此对这些元素的丰度研究具有重要的天体物理意义．到目前为止，轻元素丰度的观测结果基本上支持开放宇宙的观点．根据最新的观测结果，在本地星际介质中D丰度可能存在小尺度不均匀性，而对类星体吸收云的观测表明不同观测者所获得的原初D丰度结果最大差别可达一个量级．如果观测是可靠的，那么在目前的标准大爆炸核合成理论和星系化学演化模型框架下还不能解释这种结果．另外种种迹象表明太阳系丰度可能不代表45亿年前本地星际介质的丰度．     

Multi‐frequency solar observations at Metsähovi Radio Observatory and KAIRA

We describe solar observations carried out for the first time jointly with Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) and Aalto University Metshovi Radio Observatory (MRO). KAIRA is new radio antenna array observing the decimeter and meter wavelength range. It is located near Kilpisjärvi, Finland, and operated by the SodankyläGeophysical Observatory, University of Oulu. We investigate the feasibility of KAIRA for solar observations, and the additional benefits of carrying out multi‐instrument solar observations with KAIRA and the MRO facilities, which are already used for regular solar observations. The data measured with three instruments at MRO, and with KAIRA during time period 2014 April–October were analyzed. One solar radio event, measured on 2014 April 18, was studied in detail. Seven solar flares were recorded with at least two of the three instruments at MRO, and with KAIRA during the chosen time period. KAIRA is a great versatile asset as a new Finnish instrument that can also be used for solar observations. Collaboration observations with MRO instruments and KAIRA enable detailed multi‐frequency solar flare analysis. Flare pulsations, flare statistics and radio spectra of single flares can be investigated due to the broad frequency range observations. The Northern locations of both MRO and KAIRA make as long as 15‐hour unique solar observations possible during summer time. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Present and Future Observing Trends in Atmospheric Magnetoseismology

With modern imaging and spectral instruments observing in the visible, EUV, X-ray, and radio wavelengths, the detection of oscillations in the solar outer atmosphere has become a routine event. These oscillations are considered to be the signatures of a wave phenomenon and are generally interpreted in terms of magnetohydrodynamic (MHD) waves. With multiwavelength observations from ground- and space-based instruments, it has been possible to detect waves in a number of different wavelengths simultaneously and, consequently, to study their propagation properties. Observed MHD waves propagating from the lower solar atmosphere into the higher regions of the magnetized corona have the potential to provide excellent insight into the physical processes at work at the coupling point between these different regions of the Sun. High-resolution wave observations combined with forward MHD modeling can give an unprecedented insight into the connectivity of the magnetized solar atmosphere, which further provides us with a realistic chance to reconstruct the structure of the magnetic field in the solar atmosphere. This type of solar exploration has been termed atmospheric magnetoseismology. In this review we will summarize some new trends in the observational study of waves and oscillations, discussing their origin and their propagation through the atmosphere. In particular, we will focus on waves and oscillations in open magnetic structures (e.g., solar plumes) and closed magnetic structures (e.g., loops and prominences), where there have been a number of observational highlights in the past few years. Furthermore, we will address observations of waves in filament fibrils allied with a better characterization of their propagating and damping properties, the detection of prominence oscillations in UV lines, and the renewed interest in large-amplitude, quickly attenuated, prominence oscillations, caused by flare or explosive phenomena.     

Solar Radius Determination from Total Solar Eclipse Observations on 29 March 2006

Solar diameter measurements have been made nearly continuously through different techniques for more than three centuries. They were obtained mainly with ground-based instruments except for some recent estimates deduced from space observations. One of the main problems in such space data analysis is that, up to now, it has been difficult to obtain an absolute value owing to the absence of an internally calibrated system. Eclipse observations provide a unique opportunity to give an absolute angular scale to the measurements, leading to an absolute value of the solar diameter. However, the problem is complicated by the Moon limb, which presents asphericity because of the mountains. We present a determination of the solar diameter derived from the total solar eclipse observation in Turkey and Egypt on 29 March 2006. We found that the solar radius carried back to 1 AU was 959.22±0.04 arcsec at the time of the observations. The inspection of the compiled 19 modern eclipses data, with solar activity, shows that the radius changes are nonhomologous, an effect that may explain the discrepancies found in ground-based measurements and implies the role of the shallow subsurface layers (leptocline) of the Sun.     

The kinematic processes in solar prominences and flares and their spectral features

In this paper various models of mass motions in solar prominences and flares, such as expansion, contraction and rotation without or with depth gradients, are considered. The variation of the source function with depth is also taken into account. Under these conditions the profiles of the first Balmer lines are calculated. The various effects of mass motions on spectral lines are studied. We have established four methods for the derivation of the velocities of motions as well as their gradients from the corresponding spectral features. These methods have been preliminarily applied to observational data, mainly those of the spectra-spectroheliograph (SSHG) of the Yunnan Observatory.     

Quantitative solar spectroscopy

Quantitative solar spectroscopy must be based on calibrated instrumentation. The basic requirement of a calibration, i.e., a comparison between the instrument under test and a primary laboratory standard through appropriate procedures, will be briefly reviewed, and the application to modern space instruments will be illustrated. Quantitative measurements of spectral radiances with high spectral and spatial resolutions as well as spectral irradiances yield detailed information on temperatures, electron densities, bulk and turbulent motions, element abundances of plasma structures in various regions of the solar atmosphere – from the photosphere to the outer corona and the solar wind. The particular requirements for helioseismology and magnetic‐field observations will not be covered in any depth in this review. Calibration by a laboratory standard is necessary, but not sufficient, because an adequate radiometric stability can only be achieved together with a stringent cleanliness concept that rules out a contamination of the optical system and the detectors as much as possible. In addition, there is a need for calibration monitoring through inter‐calibration and other means (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Variability of the HeIλ5876 Å line in early type chemically peculiar stars. II

To try to understand the behavior of helium variability in Chemically Peculiar stars, we continued our on‐going observational campaign started by Catanzaro, Leone & Catalano (1999). In this paper we present a new set of time resolved spectroscopic observations of the HeI5876 Å line for a sample of 10 stars in the spectral range B3 ‐ A2 and characterized by different overabundances. This line does not show variability in two stars: HD77350 and HD175156. It shows instead an equivalent width variation in phase with the Hipparcos light curve for two stars: HD79158 and HD196502. Antiphase variations have been found in 4 stars of our sample, namely: HD35502, HD124224, HD129174 and HD142990. Nothing we can say about HD115735 because of the constancy of Hipparcos photometric data, while no phase relation has been observed for HD90044. In the text we discuss the case of HD175156, according to photometric calibration and our spectroscopic observations we rule out the membership of this star to the main sequence chemically peculiar stars. We confirm the results obtained in the previous paper for which phase relations between light, spectral and magnetic variations are not dependent on stellar spectral type or peculiarity subclass.