太阳射电精细结构高时间高频率分辨率观测研究

本文对太阳射电精细结构这一领域进行了较为详尽深入的调研 ,发现由于观测仪器技术指标 (时间、频率、频率覆盖、偏振、灵敏度等 )相对不高 ,有很多的精细结构 ,在时间上、在频率上并没有被完全分解开来 ,或是没有被检测到。对FFS的研究 ,还处于发现 -认识 -逐步深化的阶段。观测资料还很单薄。在微波高端 (厘米波段 ) ,精细结构的观测资料更是很少。另外 ,对FFS也只是有一个侧重频谱形态的分类。本文利用我国的“太阳射电宽带快速频谱仪”的观测资料 ,几年来 ,对微波频段的射电快速精细结构进行了较为深入的研究。主要研究结果有 :发现了弱偏振微波尖峰辐射中两个偏振分量之间的时间延迟和偏振反转现象 ;首次发现了微波 (短分米波段 )高偏振U型爆发并给出解释 ;首次发现了厘米波N型和M型爆发并给出解释 ;首次发现了高偏振微波斑点并给出解释 ;首次利用甚高频率分辨率频谱仪 ,通过对大样本的分米波尖峰辐射的统计 ,给出了更为可靠的、更小的相对带宽的下限 ;结合高空间分辨率的观测资料 ,对运动Ⅳ型爆发及其伴生的精细结构作了探讨 ;对双向电子束的起源及其加速位置进行了研究     

光纤阵列太阳光学望远镜偏振分析器设计

给出了满足光纤阵列太阳光学望远镜(FASOT,Fibre Arrayed Solar Optical Telescope)观测目标的偏振分析器的理论设计.它具有以下特点:(1)具备偏振光学开关功能,使得高偏振测量成为可能;(2)在750nm宽度范围内,对各Stokes偏振参量都具有50%以上的理论偏振测量效率,且总的偏振测量效率高于86.6%.使得观测者在如此宽波长范围内可对多条磁敏谱线同时进行偏振测量;(3)根据所选光球和色球线侧重于对线偏振或圆偏振的测量;(4)对偏振元件的制作工艺以及安装误差等具有相当好的容忍度.以上特性使该偏振分析器成为高性能的偏振测量设备.     

太阳射电精细结构高时间高频率分辨率观测研究

本文对太阳射电精细结构这一领域进行了较为详尽深入的调研，发现由于观测仪器技术指标（时间、频率、频率覆盖、偏振、灵敏度等）相对不高，有很多的精细结构，在时间上、在频率上并没有被完全分解开来，或是没有被检测到。对FFS的研究，还处于发现－认识－逐步深化的阶段。观测资料还很单薄。在微波高端（厘米波段），精细结构的观测资料更是很少。另外，对FFS也只是有一个侧重频谱形态的分类。本文利用我国的“太阳射电宽带快速频谱仪”的观测资料，几年来，对微波频段的射电快速精细结构进行了较为深入的研究。主要研究结果有：发现了弱偏振微波尖峰辐射中两个偏振分量之间的时间延迟和偏振反转现象；首次发现了微波（短分米波段）高偏振U型爆发并给出解释；首次发现了厘米波N型和M型爆发并给出解释；首次发现了高偏振微波斑点并给出解释；首次利用甚高频率分辨率频谱仪，通过对大样本的分米波尖峰辐射的统计，给出了更为可靠的、更小的相对带宽的下限；结合高空间分辨率的观测资料，对运动Ⅳ型爆发及其伴生的精细结构作了探讨；对双向电子束的起源及其加速位置进行了研究。     

SPIKES和FFS辐射偏振状态的快速逆转

本文简述了1991年5月16日叠加在一个47GB微波大爆发上的快速精细结构(FFS)和spike群的偏振状态.在相隔100MHz的2645、2545MHz两频率上,spike的偏振状态随时间或随频率在50～100ms量级短时标内发生快速交替变化.我们认为这可能与小尺度空间内spike辐射源区的等离子体密度出现短时标的波动及磁场强度的起伏有关.这种波动和起伏使得等离子体频率与磁迴旋频率的比值(ω_p/Q_e)在2~(1/2)附近起伏变化,从而造成电磁波X波模和O波模的电子迴旋脉塞不稳定性增长率交替支配着电磁波的辐射,产生spike 辐射偏振状态的逆转.     

1998年4月15日射电爆发中的微波Ⅲ型爆发

详细介绍了北京天文台2.6-3.8GHz太阳射电频谱仪在1998年4月15日观测到的一群微波Ⅲ型爆发。它们具有宽频带（＞100MHz）、短时标（＜100ms）、高偏振（100％）、短周期脉动（百毫秒）、内向快速频率漂移（高于1GHz/s）等显著特征。讨论了它的观测特征、时间轮廓和脉动现象，认为该群微波Ⅲ型爆发起源于等离子体基波辐射，阐述了在高频范围Ⅲ型爆发起源于等离子体基波辐射的可能性。     

耀变体在射电波段的偏振研究

利用UMRAO数据库22个耀变体源的偏振数据,根据LazarianPogosyan理论模型分析研究了耀变体射电波段的偏振随波长的变化,得出不同类的耀变体偏振随波长变化的原因。结果表明,与LazarianPogosyan理论模型吻合较好。由此得出如下结论:(1)反常去偏振耀变体源中反常法拉第旋光起主导作用,反常去偏振相对较少;(2)热辐射与同步辐射混合作用,高频波段的偏振度小于低频波段的偏振度(反常去偏振);(3)当被观测波段波长小于吸积盘热辐射对应的维恩波长时,高频波段的偏振度大于低频波段的偏振度(常规去偏振)。     

发生在5月16日太阳耀斑中的微波射电尖峰辐射

对1991年5月16日发生在2.5GHz和2.6 GHz的射电尖峰辐射的持续时间,偏振和准周期振荡等特点作统计分析,详细报导了尖峰辐射的左旋偏振和右旋偏振在2.5,2.6GHz和3.1 GHz上的贡献.在这3个频率上,大量尖峰辐射不仅迭加在微波爆发的上升和极大相上.还迭加在微波爆发的下降相上.值得注意的是,在2.5 GHz和2.6 GHz处,也迭加在发生在主微波爆发后的小爆发上.尖峰辐射持续了17分钟.描述了发生在2.5GHz和2.6 GHz上尖峰辐射的不同时间尺度的偏振反转.统计分析表明在2.5 GHz以及2.6 GHz频率上的尖峰辐射的偏振反转有不同特点,在2.5 GHz频率上的尖峰辐射偏振反转比2.6 GH早1.5分钟,并且在2.5 GHz上尖峰辐射偏振方向反转更多.     

类水星系外行星偏振特性研究

通过对不可分辨水星偏振相位曲线的研究了解类水星不可分辨系外行星的偏振特性,为用偏振探测手段寻找类水星系外行星提供有力的依据.通过贝叶斯非线性拟合得到水星测光相位曲线和偏振相位曲线,进而得到不可分辨水星的偏振相位曲线.从该曲线中得出以下结果: (1)水星在不可分辨情况下在可见光波段其偏振度的量级为10-12;(2)垂直于散射平面和平行于散射平面的最大偏振度相当,且它们所对应的相位角相对于可分辨情况下发生了明显的改变;(3)在相位角大于158°时不可分辨水星的偏振度几乎为零.     

激变射电源中偏振角快速旋转的解释

在许多激变射电源(Blazar天体)中,观测到一种非常特别的现象,即偏振角的快速旋转.在相对论喷流的框架下,这种偏振角的旋转可以用双成分模型来解释.在这个模型中,一个成分是作为背景喷流本身的辐射,是恒定不变的成分;另一个成分被认为是沿喷流传播的相对论性激波,它产生变化的流量和偏振.这两个成分的偏系辐射的叠加可以产生观测到的偏振角旋转。本文讨论了三个激变射电源(BL Lac,AO0235+164,0727-115)中发生的偏振角旋转.结果表明,用相对论喷流-激波双成分模型可以很好地拟合观测到的偏振角旋转、偏振度和流量变化。说明射电激变源中出现的快速偏振和流量变化可能是由于相对论激波沿喷流传播时,激波辐射区中磁场取向和有序性以及强度和电子密度的变化所引起的。     

伴随CME的微波爆发的特征

分析了与日冕物质抛射(CME)有关的太阳微波爆发(SMB)的特征,包括持 续时间、峰值流量、爆发类型、谱指数等．选取了从1999年11月至2003年9月的136 个事件,包括60个部分晕状CME(120°<宽度<360°)／晕状CME(宽度=360°)和 76个正常CME(20°<宽度<120°)／窄CME(0°<宽度<20°)． 研究发现: (1)与正常CME／窄CME有关的微波爆发持续时间较短,与部分晕状 ／晕状CME有关的微波爆发持续时间有长有短; (2)与慢CME有关的微波爆发持续时 间较短,与快CME有关的微波爆发持续时间可长可短;(3)与正常／窄CME有关的微 波爆发峰值辐射流量比较小,与部分晕状／晕状CME有关的微波爆发峰值辐射流量有大 有小;(4)与慢CME有关的微波爆发峰值辐射流量较小,与快CME有关的微波爆发峰 值辐射流量可长可短; (5)与正常／窄CME有关的微波爆发绝大多数为简单(simple) 型,与晕状CME有关的微波爆发绝大多数为复杂(C)／大爆发(GB)型; (6)与CME 有关的事件在频率,f相似文献   

Spike observations in flares in China

Variations on short time-scales have been found in solar flares at different wavelengths. Millisecond scale radio spikes are a quickly developing area of solar radio astronomy. The solar radio astronomy group of Beijing Astronomical Observatory (BAO) has found fine structures of microwave bursts with millisecond time-scale at 2840 MHz. In this paper, we briefly summarize the observations. A joint-observation network for observing solar radio bursts with high time resolution has also been established. The equipment in the network covers a frequency domain of more than 10:1, including 1.3, 2.0, 6, 10, 15, 20 cm, and meter wavelengths. In particular, a multi-channel polarimeter with super-fast sampling (10 s) at 2600 MHz, an intensity interferometer with 1 ms sampling rate at 6 cm wavelength, and an auto-correlation radio spectrograph with 8 ms time constant at 21 cm wavelength are being established. We pay close attention to research on the spike emission features over wide bands, and their relationship to special characteristics in other spectral ranges.     

Ferroelectric Liquid Crystal Polarimeter for High-cadence Hα Imaging Polarimetry

We developed a polarimeter with ferroelectric liquid crystals (FLCs) to observe polarization of flare kernels in the H line. Polarization is one of the important diagnostics of the high-energy particles in solar flares, and high-cadence imaging polarimetry with the precision of the order of 0.1% is required to observe the polarization of flare kernels. However, to achieve such high precision is difficult mainly due to the seeing-induced polarization error, which particularly appears around the flare kernels, because the brightness gradient is steep there. To reduce the seeing-induced error, a high modulation frequency is required, and our new polarimeter based on the combination of a high-speed CCD camera and FLCs realized high-frequency polarization modulation nearly 250 Hz. We evaluated the polarization error, and confirmed that the error was significantly reduced with the new polarimeter. We concluded that the polarimeter with FLCs meets the requirement of solar flare polarimetry.     

On polarimetry in solar active regions

The miscentering by the Doppler compensator of the Locarno polarimeter is investigated in detail. It is shown that the linear polarization is strongly falsified by this effect which also occurs at the Crimean and Izmiran polarimeters.The new design for the exit slits of the Locarno polarimeter is described. It avoids the ambiguities in the determination of the magnetic field vector that always occur when using two exit slits.A new simple electronic setup avoids most of the difficulties which are usually involved in eliminating instrumental polarization and compensating intensity fluctuations.The observational techniques for solar polarimetry at the Locarno observatory are described.To avoid mutual influences of V and U, the line centre ₀ (corresponding to V = 0 and U = max.) must coincide with the centre of slit II. Only in this case we have 234-01     

A novel quadruple beam imaging polarimeter and its application to Comet Tanaka-Machholz 1992 X

For observations of solar system objects an imaging polarimeter has been constructed as an auxiliary instrument for a f/15 focal reducer. With this instrument simultaneous measurement of theQ andU Stokes parameters is possible. It contains no moving parts such as a moving /2 retarder. The polarizer consists of two Wollaston prisms which are combined to form a single optical element. Their polarization angles differ by 45°. This compound polarizer is placed in the exit pupil of the afocal telescope-collimator system of the focal reducer and splits the exit pupil into halves. In this way four polarized beams with E-vector orientations 0°, 90°, 45°, and 135° emerge from the exit pupil. These are intercepted by the camera lens of the focal reducer system and imaged simultaneously on the CCD detector. With a properly designed field mask at the Cassegrain focus, the four beams are imaged without overlap.As a demonstration of the capabilities of this quadruple-beam Wollaston-prism polarimeter, we present observations of comet Tanaka-Machholz 1992 X in May 1992. The advantages, shortcomings, and possible improvements of the instrument are discussed.based on observations obtained at Hoher List Observatorypresently at Astronomical Observatory of Khar'kiv University, Sumskaya Street 35, 310022 Khar'kiv, Ukraine     

A solar flare X-ray polarimeter for the space shuttle

We have recently built and tested an instrument designed to measure the polarization of the hard (5–30 keV) X-ray emission from solar flares, and thereby to investigate the energy release mechanism and constrain flare models. In particular, these measurements will help to determine whether hard X-ray bursts are produced by nonthermal or by thermal electrons. The polarimeter makes use of the angular dependence of Thomson scattering from targets of metallic lithium. It has an energy resolution of a few keV, a time resolution of 5 s, and sufficient sensitivity to measure polarization levels (3) of a few percent in about 10 s for a moderate strength solar flare. The instrumental polarization has been directly measured and found to be within the design goal of 1%. This polarimeter is scheduled to be flown as part of the OSS-1 pallet on an early Space Shuttle mission.     

The Haleakala Stokes polarimeter

A versatile Stokes polarimeter for solar observations has been developed at the University of Hawaii. Recent improvements to the instrument include a high-resolution echelle spectrometer coupled to the telescope by optical fibers, and 128-element diode array detectors. The on-axis design of the telescope and polarimeter limit instrumental polarization to 10^–4, and the spectrometer detector combination provides spectral resolving power of 160000 for any wavelength between 4000 and 11000 Å. This paper describes the Haleakala polarimeter and in particular the spectrometer with its fiber-optic coupling. Examples of Stokes line profiles observed in a sunspot are presented, together with derived vector magnetic field maps.     

Development of a hard x-ray focal plane compton polarimeter: a compact polarimetric configuration with scintillators and Si photomultipliers

X-ray polarization measurement of cosmic sources provides two unique parameters namely degree and angle of polarization which can probe the emission mechanism and geometry at close vicinity of the compact objects. Specifically, the hard X-ray polarimetry is more rewarding because the sources are expected to be intrinsically highly polarized at higher energies. With the successful implementation of Hard X-ray optics in NuSTAR, it is now feasible to conceive Compton polarimeters as focal plane detectors. Such a configuration is likely to provide sensitive polarization measurements in hard X-rays with a broad energy band. We are developing a focal plane hard X-ray Compton polarimeter consisting of a plastic scintillator as active scatterer surrounded by a cylindrical array of CsI(Tl) scintillators. The scatterer is 5 mm diameter and 100 mm long plastic scintillator (BC404) viewed by normal PMT. The photons scattered by the plastic scatterer are collected by a cylindrical array of 16 CsI(Tl) scintillators (5 mm × 5 mm × 150 mm) which are read by Si Photomultiplier (SiPM). Use of the new generation SiPMs ensures the compactness of the instrument which is essential for the design of focal plane detectors. The expected sensitivity of such polarimetric configuration and complete characterization of the plastic scatterer, specially at lower energies have been discussed in [11, 13]. In this paper, we characterize the CsI(Tl) absorbers coupled to SiPM. We also present the experimental results from the fully assembled configuration of the Compton polarimeter.     

分光仪PSP0的偏振器设计与实验

本文介绍人光仪ＰＳＰ０ 的偏振器设计和实验结果。偏振器设计为旋转半滤片加固定偏振片的系统,但在选用偏振器件方面提出了两种方案。对于低价设计的实验结果表明,偏振器可在４３０７８０ｎｍ 波长范围内工作,能够实现ＰＳＰ０ 在其最佳工作波长的偏振测量。     

LONG-TERM VARIATIONS OF THE TORSIONAL OSCILLATIONS OF THE SUN

We investigated long-term variations of the differential rotation of the solar large-scale magnetic field on 1024 H charts in the latitude zones from +45° to -45° in the period 1915–1990. We used the expansion in terms of Walsh functions. It turns out that the rotation of the Sun becomes more rigid than average during the cycle maximum and the rotation is more differential during minimum. From 1915 to 1990, 7 bands of faster- and 7 bands of slower-than-average rotation are revealed showing an 11-year period. These bands drift towards the equator: 45° in 2.5 to 8 years. The time span of the bands varies from 4 to 6.8 years and is in anti-phase with long-term solar activity. The latitude span of the bands of torsional oscillations varies from 0.5 R to 1.3 R and shows a long-term variation of about 55 years. The poloidal component of velocity, V varies from 2 ms ^-1 to 6 ms ^-1. The maximum rate of the equatorial drift occurs in the period between 1935 and 1955 and it develops prior to the highest maximum activity. At the modern epoch from 1965 to 1985, V does not exceed 3 ms ^-1, but now it has a tendency to increase. The bands of slower-than-average rotation correspond to the evolution of the magnetic activity towards the equator in the butterfly diagram.