非均匀喷流模型及其在BL Lac天体中的应用

在非均匀锥形喷流模型中,电子数密度、磁场强度随着到喷流顶点的距离呈幂律分布.该模型能成功解释活动星系核喷流核心区域的平谱射电辐射,但已有的模型计算只适用于喷流运动方向与视线夹角很大的情况,所以需要建立适用于任何视角情况的非均匀锥形喷流辐射计算公式.普遍认为BL Lac天体中喷流的运动方向与视线夹角很小,推广后的非均匀喷流模型拟合了3个BL Lac天体的射电观测谱,确定了它们喷流中电子数密度、磁场强度等物理参数.研究结果表明观测辐射谱拐折频率确定出锥形喷流离黑洞最近距离,对于这3个BL Lac天体,它们的锥形喷流离黑洞最近距离约为Schwarzschild半径.     

同步-自康普顿谱的相关性分析

有一些射电源同时观测到射电辐射和紫外-X射线辐射,某些作者认为这两种辐射起源于同步一自康普顿效应。本文给出该效应中同步射电谱与康普顿紫外-X射线谱的一系列相关性。分析这些相关性,可以提供一些半定量的理论判据,用以检验同步一自康普顿效应的正确性。这种分析也有利于估计源的各种物理参量。     

武仙座X-1可能存在软X射线或远紫外波段的谱线

在双星系统X射线源HerX-1的硬X射线波段测量到强的X射线谱线.第一条谱线在58keV,第二条谱线在110keV附近,并给出了谱线宽度,强度比和流量.对这种现象可以有几种解释,其中之一是认为这些谱线是由强磁场中量子化的电子同步加速辐射产生,从而可以推导出发射区的磁场强度.这几乎可以认为是宇宙中存在强磁场的     

太阳射电爆发现象中的电子回旋脉泽辐射

太阳射电爆发(Solar Radio Burst, SRB)是太阳高能电子与背景等离子体相互作用产生的感应辐射现象,其多样的动力学谱类型及其复杂的精细结构反映了辐射源区磁等离子体结构状态丰富的物理信息,而相关辐射机制则是解读相关物理信息的关键工具.长期以来,在SRB辐射机制的研究中一直存在着争议不决的两种主要机制,即等离子体辐射机制和电子回旋脉泽(Electron Cyclotron Maser, ECM)辐射机制.近年来,针对传统的ECM辐射机制应用到SRB现象时遇到的一些主要困难,发展了由幂律谱电子低能截止驱动和包含快电子束自生阿尔文波效应的新型ECM驱动模型,并成功应用于解释各类不同SRB动力学谱的形成机制.基于这些新型的ECM辐射模型,系统地总结了ECM辐射机制在各种不同类型SRB现象中的应用,并对它们不同动力学谱结构的形成给出了一致统一的物理解释.     

太阳微波爆发区磁场强度诊断和误差分析

本文分析了前人利用Dulk和Marsh的射电微波爆发谱极大频率Vp近似式求解磁场强度B的方法（我们简称两参数法）在数学、物理上存在解不唯一和不自洽的问题，且相对误差高达-3．0±5．3．而我们最近提出的利用一套完整的微波爆发谱谱参数（Vp、β和Tbv）决定磁场的方法，亦即三参数法，具有B的唯一解和自洽解，精度高达±0．48．     

同步辐射瑞利-金斯波场对高能电子加速

由分析可知，在光学厚的介质中麦氏分布的极端相对论电子在磁场中能产生同步加速辐射，其辐射谱为瑞利—金斯谱．基于Fokker-Planck方程，这种波场对快电子的加速将产生幂律分布的电子能谱．考虑到日冕活动区的物理条件，在太阳耀斑中观测到的10Mev左右的电子能谱很可能就是由同步加速辐射加速快电子产生的．     

武仙座X-1的硬X射线谱线

本文应用对武仙座X射线源 Her X-1新近获得的硬X射线谱线的观测资料,对辐射区域的物理情况作了初步的探讨。得到:辐射区域对谱线辐射是不透明的,激发温度T～2.4×10~8K,辐射区域的截面积～2×10~7厘米~2,并预言第三条谱线的强度约为第一条谱线的1/13,第三条谱线的宽度约为第一条谱线的3倍。     

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。     

猎户座中SiO脉泽分布的新模型

我们研究了Orion-IRc2SiO脉泽饱和辐射谱线轮廓，找到了很好的拟和谱线轮廓的函数．在观测结果中发现，Orion－IRc2SiO脉泽饱和辐射谱线轮廓中存在着若干峰，为了解释这一现象，我们提出了一个新的分布模型，即多重分离的旋转膨胀盘壳模型.计算结果表明，这个新模型，不仅可以解释脉泽的非饱和辐射谱，而且可以解释脉泽的饱和辐射谱.     

星际γ射线谱线辐射流量的估算和来源探讨（Ⅱ）：—新星,SNIa的贡献和…

运用四种星体空间分布模型和新星（及ＳＮＩａ）的最新核物理数据，计算了它们所产生的（５条）γ射线谱线辐射流量及核素丰度。结果表明，如果只根据“物理因子”上限，新星可能成为＾２６Ａｌ的主要来源之一，然而由于核素丰度值的要求，新星模型本身仍存在难以克服的困难，另还指出，谱线轮廓的研究也将为本文探讨的问题提供重要判据。     

Magnetic field strength estimation in synchrotron radiation sources

In this paper a method of estimating the magnetic field strength,B, in a homogeneous microwave burst source with simplified expressions for the synchrotron radiation is presented. An approximate formula of the magnetic field is obtained using the method. Once the magnetic field is estimated the total number of energetic electrons along the line of sightN L can be estimated also. The errors ofB andN L have been given. It is found that this method is useful for semiquantitative investigations of models of radio burst sources.     

Diagnostics and error analysis of the magnetic field strength in solar microwave burst regions

This paper points out that the previous method of finding the magnetic field strength using the approximate formula of the maximum frequency of microwave burst of Dulk and Marsh gives non-unique and self-inconsistent results, and with relative errors as high as −3.0±5.3, whereas my recently proposed three-parameter (ν_p, β, T) method will give unique and self-consistent solutions of the field strength, with greatly reduced errors (±0.48).     

一个微波爆发的源区磁场和高能电子的能流估计

本文分析了１９９３年１０月２日０７：３９：４０－０７：４１：００ＵＴ时段太阳产生的一个多脉冲微波暴的观测，认为它是由多个脉冲爆发叠加在一个慢变爆发背景上组成的．根据谱分析和利用我们的日冕磁场诊断公式［１］，第一次获得了一个爆发源区的磁场强度和高能电子的信息，其主要结果是：（１）脉冲爆发分量在光薄部分的射电谱指数的平均值比慢变爆发背景的值小１，即前者的谱比后者的硬．在１９．６ＧＨｚ上的亮度温度前者比后者高６倍．（２）从脉冲爆发分量和慢变爆发背景分量推断的源区磁场平均值分别为１５８和５３１高斯，且发现在爆发期间，慢变暴源区磁场强度随时间圣马鞍形变化，在极大相的值比脉冲相和下降相低约５０％（３）产生脉冲暴分量的高能电子的柱密度ＮＬ和数密度Ｎ（＞Ｅ０）分别为慢变暴分量的４％和８％，但它们所携带的能流和发射系数要比慢变爆发分量的值高１倍和８倍！表明这两种爆发成份可能分别来自能谱不同的两群电子在不同爆发源区的辐射．     

The magnetic field strength and energy flux of energetic electrons in a microwave burst source region

The observations of a microwave burst with multiple impulses on 1993 Oct 2, 073940–074100 UT are analysed. This event consists of multiple impulses superimposed on a slowly varying burst background. Our formula for coronal magnetic field diagnostics was used here for the first time to derive the field strength and information on the energetic electrons. The results are: 1) The mean spectral index of the impulsive component in the optically thin part is less than that of the slow background by 1 (a harder spectrum). The mean brightness temperature at 19.6 GHz of the former is 6 times that of the latter. 2) The mean magnetic strengths of the impulse and slow burst regions are 158 G and 531 G, respectively. The time variation in the slow burst region is saddle-shaped, being 50% lower in the middle than at the beginning and end. 3) The column density NL and number density N of energetic electrons in the impulsive component are 4% and 8% of those of the slow component, but the energy flux and emission coefficient are 100% and 800% greater. The two components appear to be produced by two different electron groups with different energy distributions in two different regions.     

Diagnosis of coronal magnetic field with data of Nobeyama Radio Heliograph

The expression is derived for the coronal magnetic field strength from the observations of brightness, temperature, peak frequency, spectral index, and polarization degree of solar microwave bursts. One example of solar burst on November 28, 1998 is given for the calculation of coronal magnetic field from the data of Nobeyama Radio Heliograph (NoRH). The results are comparable with the SOHO/MDI magnetogram and the calculation from the Nobeyama Radio Polarimeters (NoRP), as well as the coronal loops in SOHO/EIT and YOHKOH/SXT images. Therefore, it may be the first time that the two-dimensional diagnosis of coronal magnetic field in a microwave burst source from the radio observations has been made.     

The intensity decrease of microwave bursts

A typical microwave burst on 1968 January 11, 1700 UT is used to demonstrate that the radiation spectrum at maximum phase can be described by gyromagnetic absorption. A model for the source is derived from the observed spectrum. With the aid of this model, we try to explain the decreasing phase of the burst intensity. Satisfactory agreement with observation is obtained, when one assumes that the cooling of the burst plasma is caused by heat conduction parallel to the magnetic field lines.     

The Energetic Spectrum of Non-Thermal Electrons in an Acceleration Region Calculated From a Solar Microwave Type III Burst with both Positive and Negative Frequency Drifts

A typical event of solar microwave type III burst with both positive and negative frequency drifts was observed by the 1–2 GHz spectrograph at Beijing Observatory on January 5, 1994. The separatrix frequency (1.3 GHz) may correspond to an acceleration region. The energy of the electron beam responsible for the burst is calculated from the drift rate and the height of the source above the photosphere. Moreover, if the solar microwave type III burst is explained by the beam-plasma instability as suggested by Huang (1998), the energy density as well as the particle density of the electron beam may be estimated from the burst flux, the growth rates and the modularity (Huang et al., 1996). So that, a very good power- law distribution is simulated for the energetic spectrum of the electron beam in this event with a spectrum index 4.5. The electron beam may be accelerated by an electric field with a length of 10⁷ m and a strength of <10-4 V m- 1. These results are necessary for understanding the acceleration process in solar flares. This revised version was published online in July 2006 with corrections to the Cover Date.     

The self absorption of gyro-synchrotron emission in a magnetic dipole field: Microwave impulsive burst and hard X-ray burst

The gyro-synchrotron emission from a model source with a non-uniform magnetic field is computed taking into account the self absorption. This model seems adequate not only to interpret the radio spectrum and its time variation of microwave impulsive bursts but also to solve the discrepancy between the numbers of non-thermal electrons emitting radio burst and those emitting hard X-ray burst.The decrease of flux of radio burst with decreasing frequency at low microwave frequencies is due to the self absorption and/or the thermal gyro-absorption. In this frequency range, the radio source is optically thick even at weak microwave bursts. The weakness of the bursts may be rather due to the small size of the radio source and/or the weakness of the magnetic field than the small number density of the non-thermal electrons.The time variation of the flux of radio burst may be mainly attributed to the variation of source size in a horizontal direction ( direction) instead of the variation of the number density of non-thermal electrons itself, implying that the acceleration region progressively moves in the horizontal direction leaving the non-thermal electrons behind during the increasing phase of the radio burst.     

On the Microwave Spike Emission of the September 6, 1992 Flare

The main aim of this paper is to estimate, from multispectral observations, the plasma parameters in a microwave burst source which was also the site of spike emission. This information is essential for the determination of the spike emission process. By analyzing one-dimensional source distributions observed with the SSRT at 5.7 GHz and correlating them with Yohkoh X-ray and Nobeyama 17 GHz images, we have concluded that the microwave emitting region was larger than the soft X-ray loop-top source, and that the origin of the burst could be explained by gyrosynchrotron emission of non-thermal electrons in a magnetic field of approximately 100 G. It has been shown that the source of 5.7 GHz spikes observed during the burst was located close to an SXR-emitting loop with high density and temperature and a relatively low magnetic field. Thus, plasma emission is the most favourable radiation mechanism for the generation of the sub-arc-second microwave pulses.     

A two-component model of impulsive microwave burst emission consistent with soft and hard X-rays

A two-component (core-halo) emission model has been applied reconciling hard and soft X-ray burst emissions with the microwave burst radiation. The core region is represented by a nonthermal energy distribution (Maxwellian+power law tail) and assumed to be surrounded by a thermal halo. Parameters characterizing the energy distribution and emission measures have been derived numerically from soft and hard X-ray measurements. Using an artificial magnetic field model the microwave flux spectrum has been calculated on the basis of gyro-synchrotron emission and absorption by solving the equation of radiation transfer along the ray trajectories. Open parameters were used to adapt the spectrum to the radio measurements.Thus probable informations about the most appropriate magnetic field parameters as well as about the time- and frequency- dependent source diameters (yielding growth velocities of the core region during the impulsive phase) are deduced for the burst of 1972 May 18 as an example. A fit of the observed spectrum at the burst maximum is consistent with a magnetic field of 150O G at the core centre decreasing up to about 40 G at the top of the halo at a height of 50 000 km above the centre, a core density of 10¹⁰ cm^–3 decreasing to 10⁹ cm^–3 at the outer halo boundary, and a core diameter of 15 000 km (]20).Due to the simple geometry and emission process adopted,- the model refers primarily to special impulsive bursts. For the representation of broad band microwave bursts, e.g. type IV , events, a more complex source geometry and/or other variants of the emission mechanism must be invoked.