共查询到18条相似文献，搜索用时 171 毫秒
1.
首先考察了谱线形成深度理论及其在诊断太阳大气中矢量磁场分层结构方面的应用,指出了分别与贡献函数和响应函数相关的方法的优缺点,然后用理论斯托克斯轮廓观察各轮廓参量沿视线方向梯度对轮廓尤其是它的对称性和极值点的影响,在此基础上提出了基本假设使偏振辐射转移方程在极值点得到极大的简化而创立了一种不依赖形成深度理论的新方法。它由四个操作构成,将其中三个操作作循环处理便可得到位于所考虑的沿深度方向格点化的层次上的各轮廓参量及表面以下不能观测到的斯托克斯轮廓。整个推导采用层层往下递推模式,导出的结果以矢量磁场尤其是场强大小最令人满意。作者分别用理论轮廓和实测轮廓作了拟合,结果发现拟合轮廓在所利用的谱线非远线翼部分与被拟合轮廓相符较好,能导出比较复杂的磁结构。但本方法也存在导出的深度范围不广及推导表面不能精确定位等问题。 相似文献
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首先考察了谱线形成深度理论及其在诊断太阳大气中矢量磁场分层结构方面的应用,指出了分别与贡献函数和响应函数相关的方法的优缺点,然后用理论斯托克斯轮廓观察各轮廓参量沿视线方向梯度对轮廓尤其是它的对称性和极值点的影响,在此基础上提出了基本假设使偏振辐射转移方程在极值点得到极大的简化而创立了一种不依赖形成深度理论的新方法。它由四个操作构成,将其中三个操作循环处理便可得到位于所考虑的沿深度方向格点化的层次上 相似文献
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一种根据斯托克斯轮廓分析推导太阳矢量磁场和热力学参量的空间三维结构的新方法在本文中提出．在不考虑散射和原子偏振的假设下，该方法由三个具有不同功能的操作分别作用于太阳大气中一层或二层斯托克斯轮廓组成．这三个操作构成一个运行单元．将此单元运用到从表面到光球底层所划分的大气层格点，然后对扫描区所有的点应用同样的程序便可获得太阳上观察区的矢量磁场和热力学参量的空间三维结构．文中给出了相应的流程图和三个操作的详细描述，并用简化了的程序对理论轮廓进行了拟合．结果表明此方法能较满意地导出矢量磁场尤其是磁场强度的三维空间结构，而热力学参量结构的推导还需进一步改进． 相似文献
4.
本文在考虑磁光效应的条件下,选用合适的太阳黑子模型,对Fel λ6302.499等磁场敏感谱线,求得四个斯托克斯参数转移方程组的数值解。此外,本文建立由斯托克斯参数轮廓直接推求向量磁场信息(包括磁场强度、磁场方向与视线的夹角以及磁场方位角)的方法。 相似文献
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脉冲星的偏振信息是理解脉冲星辐射区的重要手段，利用澳大利亚的64m射电望远镜进行大量的脉冲星观测，得到了一批脉冲星的偏振轮廓和偏振参数，编辑了几乎所有发表的脉冲星轮廓资料，系统总结了脉冲星圆偏辐射的规律，为理论上解释脉冲星辐射这一重要难题提供观测依据和物理限制，利用脉冲星作为探针，研究了银河系磁场结构和模型，确定了银河系BS磁场模型，发现了银河系上下反对称的环向磁场，并首次对星系尺度的发电机类型进行判别，证认出A0型发电机运行于银河系，发现了银晕中的垂直磁场和M31及银盘中的非常延展的磁场，探测到NGC2997星系中由内到外的旋涡磁场，并提出可能有两种发电机在这个星系的不同区域运行。 相似文献
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为了建立三维的太阳黑子磁场模型，必须确定横向磁场的方位角（x)及其随深度的可能变化。本文提出一种探测x随深度变化的方法，即对黑子的一定点依次用磁敏谱线的不同部分测量代表线偏振的两个斯托克斯参数Q和U，然后按由牧田提出并经我们改进的方法，给出磁场方位角图。如果x随深度呈现出扭曲结构，则方位角图上的曲线含有圆圈形，否则可是类似抛物线的较为简单的曲线。在测量仪器的灵敏度足够的情况下，本方法对黑子外面的日面弱磁场区域也可以使用。 相似文献
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本文把我们在文[1]和[2]中建立的诊断方法,应用于美国高山天文台斯托克斯参量仪对1978年12月11日太阳黑子本影和半影取得的Q和U两个参数的轮廓,发现这个黑子的磁力线不呈现较强的扭绞。 相似文献
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《天文研究与技术》2021,(4)
磁场是太阳爆发活动的根本驱动力,高精度实时偏振测量是实现磁场测量的常用方法。常用的波片式测量方法需要进行多次测量,因存在机械旋转结构,易导致仪器抖动,降低测量精度;波片旋转或切入切出也会导致测量时间较长。目前,基于磷酸二氘钾(DKDP)晶体和波片的太阳大气偏振测量周期较长,实时性不高,无法应用于快速变化的太阳活动磁场探测。根据以上背景,提出了一种基于双DKDP晶体原理的太阳大气实时偏振探测技术,采用两片快轴方向不同的DKDP晶体,通过外加不同电压进行快速相位延迟变化,实现对入射太阳光的偏振调制,获取太阳大气偏振的斯托克斯(Stokes)矢量。相较于传统旋转波片与DKDP晶体相结合的方法,本文提出的方法可将单次偏振调制速率从数秒提高到毫秒级,极大地提高了太阳磁场测量的实时性。仿真分析结果表明,本文提出的方法测量精度达到2×10~(-3),单波长点测量时间分辨率提高了20倍以上,可以实现对太阳磁场偏振信息的实时精确测量。 相似文献
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A simple method is proposed to infer the vector magnetic field at the surface of the Sun from Stokes profiles. This is based on the assumption that the variations of thermodynamical and magnetic field parameters with depth near the surface are so small that the displacements of the wavelengths at which the Stokes profiles reach their extrema can be ignored. And hence the polarized radiative transfer equations are greatly reduced to a set of non-linear equations with vector magnetic field parameters (, , ) which can be solved by a numerical iteration method. By fitting the synthetic profiles, it is shown that this proposed method can produce information on the vector field at the surface. It is also used to revise the observed profiles and it is found that the observed sunspot has the magnetic field structure of the fan model with the lines of magnetic field twisted. 相似文献
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The polarization-free (POF) approximation (Trujillo Bueno and Landi Degl'Innocenti, 1996) is capable of accounting for the approximate influence of the magnetic field on the statistical equilibrium, without actually solving the full Stokes vector radiative transfer equation. The method introduces the Zeeman splitting or broadening of the line absorption profile I in the scalar radiative transfer equation, but the coupling between Stokes I and the other Stokes parameters is neglected. The expected influence of the magnetic field is largest for strongly-split strong lines and the effect is greatly enhanced by gradients in the magnetic field strength. Formally the interaction with the other Stokes parameters may not be neglected for strongly-split strong lines, but it turns out that the error in Stokes I obtained through the POF approximation to a large extent cancels the neglect of interaction with the other Stokes parameters, so that the resulting line source functions and line opacities are more accurate than those obtained with the field-free approach. Although its merits have so far only been tested for a two-level atom, we apply the POF approximation to multi-level non-LTE radiative transfer problems on the premise that there is no essential difference between these two cases. Final verification of its validity in multi-level cases still awaits the completion of a non-LTE Stokes vector transfer code.For two realistic multi-level cases (CaII and MgI in the solar atmosphere) it is demonstrated that the POF method leads to small changes, with respect to the field-free method, in the line source functions and emergent Stokes vector profiles (much smaller than for a two-level atom). Real atoms are dominated by strong ultraviolet lines (only weakly split) and continua, and most lines with large magnetic splitting (in the red and the infrared) are at higher excitation energies, i.e. they are relatively weak and unable to produce significant changes in the statistical equilibrium. We find that it is generally unpredictable by how much the POF results will differ from the field-free results, so that it is nearly always necessary to confirm predictions by actual computations.The POF approximation provides more reliable results than the field-free approximation without significantly complicating the radiative transfer problem, i.e. without solving any extra equations and without excessive computational resource requirements, so that it is to be preferred over the field-free approximation. 相似文献
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The application of Unno's (1956) solution of the transfer equation for polarized radiation to the determination of thevector magnetic field is investigated. An analysis procedure utilizing non-linear least squares techniques is developed that allows one to automate the reduction of measured spectral profiles of the Stokes parameters to determine the field angles, strength as well as other parameters. The method is applied to synthetic spectra generated using a model solar atmosphere and yields results of remarkably high accuracy. The influence of additional factors upon determination of the vector field are also considered. These factors include effects of asymmetric profiles, magneto-optical effects, magnetic field gradients, unresolved field elements, scattered light, and instrumental noise.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
14.
Various spectropolarimetric observations show peculiar Stokes profiles that reveal the coexistence of at least two magnetic components in the same resolution element. An example is given by observations of the full Stokes vector in a complex active region performed with the ZIMPOL I Stokes polarimeter. In order to deduce the physical parameters of the observed regions from such measured profiles, we have extended an existing inversion code, so that it can now fit the data with models composed of up to three different atmospheric components. Two of these components are magnetic and may possess different field strengths, field geometries, temperature stratifications, and velocity fields. The third component describes the field free atmosphere surrounding the magnetic features.The so extended inversion code has then been applied to the ZIMPOL I data. In this paper we present and discuss sample fits. The code is able to reproduce the observed complex Stokes profiles with good accuracy and provides physical parameters for both of the coexisting magnetic atmospheres. Inversion tests with a 2-component model (with one magnetic and one non-magnetic component) applied to the same profiles do not reproduce the measurements sufficiently well. 相似文献
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The system of transfer equations of the four Stokes parameters I, Q, U, V under the action of the magneto-optical effect (i.e. the Unno-Beckers equations) are numerically solved in this paper for the magneto-sensitive lines FeI λλ 6302.499 and 5324.191 using an appropriate sunspot model. The errors in the expressions for the coefficients r and W in Beckers' paper [2] have been corrected for. From the results of calculations, features of the profiles of the Stokes parameters dependent on the magnetic vector have been isolated. Our computations also show that the magneto-optical effect should be taken into consideration in the measurement of the vector magnetic fields.
In the fourth section of this paper we have established a simple and convenient method for obtaining-information on the magnetic vector (including the field strength B, its inclination to the line of sight γ and its azimuth χ) from the profiles of the Stokes parameters. It consists of three steps: (1) The value of B is determined from the distance of the highest point in the V-profile from the central line. (2) γ is then found from Vmax, i.e maximum value of V. (3) Lastly, the angle χ is found from Q0, i.e. the value of Q at line centre. 相似文献
17.
Thomas G. Moran Donald E. Jennings L. Drake Deming George H. McCabe Pedro V. Sada Robert J. Boyle 《Solar physics》2007,241(2):213-222
We present the first solar vector magnetogram constructed from measurements of infra-red Mg I 12.32-μm line spectra. Observations
were made at the McMath-Pierce Telescope using the Celeste spectrometer/polarimeter. Zeeman-split Stokes line spectra were
fitted with Seares profiles to obtain the magnetic field parameters. Maps of absolute field strength, line-of-sight angle,
and azimuth are presented. Analysis shows that the variation in field strength within a spatial resolution element, 2 arcseconds,
is greatest in the sunspot penumbra and that this is most likely caused by vertical field strength gradients, rather than
horizontal image smearing. Widths of the Zeeman-split σ components, assuming a formation layer thickness of 200 km, indicate that vertical field strength gradients can be as large
as 6.5 G/km in a penumbra. 相似文献
18.
The inversion routine proposed by Aueret al. (1977), for the determination of vector magnetic fields from Stokes profiles, has been generalized to include magneto-optical and damping effects. Synthetic profiles have then been generated from a sunspot model atmosphere accounting for the depth variation of the relevant physical parameters such as the magnetic field amplitude, inclination angle, etc...., each variation being considered one at a time. Alfvén waves and magnetic inhomogeneities over the field of view have also been considered. These synthetic profiles have been presented to the inversion routine. The results of the fits show that the magnetic field amplitude and direction are always recovered with good accuracy when these quantities are constant in the model atmosphere, and, in those cases where te magnetic field vector is supposed to vary monotonically with optical depth, the values recovered are always intermediate between the values corresponding to the top and bottom of the atmosphere. Moreover, we found that the differences between synthetic and best-fit profiles are able to characterize, in many cases, the particular physical situation considered. 相似文献