Chromospheric evolution and the flare activity of super-active region NOAA 6555

Super-active region NOAA 6555 was highly flare productive during the period March 21st–27th, 1991 of its disk passage. We have st udied its chromospheric activity using high spatial resolution Hα filtergrams taken at Udaipur along with MSFC vector magnetograms. A possible relationship of flare productivity and the variation in shear has been explored. Flares were generally seen in those subareas of the active region which possessed closed magnetic field configuration, whereas only minor flares and/or surges occurred in subareas showing open magnetic field configuration. Physical mechanisms responsible for the observed surges are also discussed.     

VLA and MERLIN observations of RZ Cassiopeiae

We present radio interferometric observations of the Algol-type binary system RZ Cassiopeiae made with the VLA and MERLIN arrays at 6 cm over an incomplete orbital cycle of the system (1.195 d). We detected RZ Cas with both instruments. The images were unresolved in both cases, with angular extents comparable to the synthesized beams. The peak flux density in the VLA image was 1.14 mJy beam⁻¹ and in the MERLIN image it was 0.93 mJy beam⁻¹. The derived brightness temperatures are  4.02 × 10⁸  and  4.35 × 10⁸ K  and the effective electron energies are 0.347 and 0.346 MeV for the MERLIN and VLA data respectively. The radio light curve shows an interesting modulation centred close to the primary eclipse which seems to correlate with ASCA SIS observations of the system. The results can be interpreted as an emitting region on the outer hemisphere of the cool component aligned along the centroid axis of the binary system.     

X-ray spectroscopy of stellar coronae

Summary From the early discovery in 1948 of X-rays from the Solar corona, X-ray spectroscopy has proven to be an invaluable tool in studying hot astrophysical and laboratory plasmas. Because the emission line spectra and continua from optically thin plasmas are fairly well known, high-resolution X-ray spectroscopy has its most obvious application in the measurement of optically thin sources such as the coronae of stars. In particular X-ray observations with theEINSTEIN observatory have demonstrated that soft X-ray emitting coronae are a common feature among stars on the cool side of the Hertzsprung-Russell diagram, with the probable exception of single very cool giant and supergiant stars and A-type dwarfs. Observations with the spectrometers aboardEINSTEIN andEXOSAT have shown that data of even modest spectral resolution (/ = 10–100) permit the identification of coronal material at different temperatures whose existence may relate to a range of possible magnetic loop structures in the hot outer atmospheres of these stars. The higher spectral resolution of the next generation of spectrometers aboard NASA'sAXAF and ESA'sXMM will allow to fully resolve the coronal temperature structure and to enable velocity diagnostics and the determination of coronal densities, from which the loop geometry (i.e. surface filling factors and loop lengths) can be derived. In this paper various diagnostic techniques are reviewed and the spectral results fromEINSTEIN andEXOSAT are discussed. A number of spectral simulations forAXAF andXMM, especially high-resolution iron K-shell, L-shell, and2s-2p spectra in the wavelength regions around 1.9 Å, 10 Å, and 100 Å, respectively, are shown to demonstrate the capabilities for temperature, density, and velocity diagnostics. Finally, iron K-shell spectra are simulated for various types of detectors such as microcalorimeter, Nb-junction, and CCD.     

风云二号F星太阳X射线探测器在轨探测初步成果

风云二号系列卫星以自旋稳定方式工作于地球静止轨道,太阳X射线探测器是该系列卫星的重要有效载荷,监测太阳耀斑爆发过程,并对太阳质子事件等灾害性的空间天气事件进行预警.卫星自旋一周,该探测器完成一次全日面观测,记录太阳X射线的能谱与流量.2012年初,太阳活动进入第24周峰年,风云二号卫星太阳X射线探测器的在轨运行取得了良好的观测结果.相比于过去的太阳X射线探测器,风云二号F星的太阳X射线探测器应用了硅漂移探测(Silicon Drift Detector,SDD)技术,对GEO轨道海量的高能带电粒子采取了有效的屏蔽措施,可以对更"软"的X射线进行观测,能谱分辨率本领达到国际先进水平,对太阳耀斑的量化定级精度更高,在轨初步观测结果表明,精确的能谱探测能力可提高太阳质子事件预警能力,能道响应的时间特性比过去的探测数据更准确地反映了太阳耀斑的加热过程和带电粒子加速特性.本文介绍了风云二号F星太阳X射线探测器的设计及其发射前的标定试验结果,并且对发射后在轨运行获得的初步探测成果进行分析和讨论.     

1989年8月17日耀斑后环系速度场分析

本文给出了１９８９ 年８ 月１７ 日耀斑后环的观测视向速度场,在环内物质在太阳重力、磁场梯度和大气压力梯度联合作用下沿环腿螺旋上升和环内物质密度由环腿向环顶和环足线性递增的假设下,理论上计算了该环系的视向速度场,理论计算和观测结果基本相符,似乎为耀斑物质由色球蒸发作上升运动的观点提供了间接的例证     

边缘耀斑中HeI 10830的加宽计算

讨论了 ＨｅＩ １０８３０Ａ的 Ｄｏｐｐｌｅｒ和 Ｓｔａｒｋ加宽机制以及各种加宽参数的计算，并 得到以下一些结论：辐射阻尼对 ＨｅＩ １０８３０ Ａ的加宽作用与 Ｄｏｐｐｌｅｒ效应相比可以忽略； 在公认的耀斑电子密度（Ｎｅ＝３．２ ×１０１３ｃｍ－３）的情况下，所有阻尼项均不可能产生可以 觉察的加宽；直到 Ｎｅ＝１０１５ｃｍ－３，各种阻尼对线心半宽的增加都不起作用，其值最多 在１０－３的量级，因此；线心都可以看作是Ｄｏｐｐｌｅｒ加宽；当 Ｎｅ＞１０１４ ｃｍ－３时，Ｓｔａｒｋ 加宽，特别是电子碰撞的 Ｓｔａｒｋ加宽将在 ＨｅＩ １０８３０ Ａ的加宽中起主要作用；如要 Ｓｔａｒｋ 加宽谱线的线翼比纯Ｄｏｐｐｌｅｒ加宽大１－２倍，则阻尼加宽半宽与。可以相比拟；如果 用 Ｓｔａｒｋ加宽来解释 １９８９年边缘耀斑的观测轮廓，则电子密度将达１０～（１７）ｃｍ－３，与氦 原子的碰撞阻尼（γ３）造成的加宽对Ｉ１２和Ｉ３两分量明显不同，它们对Ｉ１２的影响比对Ｉ３ 的影响大近一个量级，我们的观测显示Ｉ１２和Ｉ３线翼的延伸基本一样，因而我们的观测 轮廓不可能是γ３造成的     

一个边缘耀斑(后)环系速度场的近似计算

利用“多云模型”方法,从云南天文台二维多波段太阳光谱仪观测到的Ｈβ光谱资料中导出１９８９年８月１７日太阳西边缘的一个大的耀斑环系不同时间的视向速度场．为了解释观测速度场的主要特征,本文采用如下假设和近似：环内物质在太阳重力、磁场应力和环内气压梯度力联合作用下由环足沿螺旋磁力线上升运动．应用ＭＨＤ理论计算了它的理论速度场．通过两者的比较发现,计算出的速度场与第一时段的观测速度场基本相似,这似乎对耀斑物质蒸发模型提供了支持．     

Detection of transient high frequency optical oscillations of the flare star YZ CMin

In this paper we present the results of the analysis of the B ‐light curve for the flares of the red dwarf YZ CMin (dM4.5e), which were observed on February of 2002, with the help of the 30‐inch Cassegrain telescope of the Stephanion Observatory, Greece. Discrete Fourier Transform analysis and the use of the Brownian Walk noise enable us to estimate the proper random noise and detect possible weak transient optical oscillations. Our results indicate that: (1) Transient high frequency oscillations occur during the flare event and during the quiet‐star phase as well. (2) The observed frequencies range between 0.0083 Hz (period 2 min) and 0.3 Hz (period 3 s) is not rigorously bounded. The phenomenon is most pronounced during the flare state. (3) During the flare state: (a) Oscillations with period 2 to 1.5 min, 60 s, 11 s, 7.5 s, and 4 s appear around the maximum light state and persist during the whole flare state, (b) from the flare maximum phase on, a progressive increase of oscillations with periods 30 s, 20 s down to 4.0 s is markedly indicated, and (c) at the end of the flare only the oscillation of the pre‐flare state do remain. Our observations are consistent with the phenomenology of impulsively exited oscillations on a coronal magnetic loop and subsequent chromospheric heating by electronic flux at the foot of the loop or/and by soft X‐ray coronal emission. Our observation give evidence that more than one impulsive events may occur in the course of an observed flare (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

太阳宇宙线高能电子能谱的形成

提出了一个太阳脉冲和经变耀斑中高能太阳宇宙线电子能谱的形成模型，探讨了高能电子通过日冕捕获区的库仑损失、轫致辐射和同步辐射等物理过程，首次研究了日冕等离子体尾场对太阳宇宙线电子的加速及其能谱的形成．所得结果和观测谱能很好地符合，从而较合理地阐明了脉冲耀斑和经变耀斑两类太阳宇宙线高能电子谱的结构．     

Multi-wavelength Diagnostics of Bombardment by Non-thermal Particles in Solar Flares

Chromospheric lines, including Ha, Lyα, Lyβand CaⅡK, CaⅡ8542, are systemically and quantitatively investigated with respect to the non-thermal excitation and ionization due to particle beam bombardment for a series of solar semi-empirical atmospheric models. As a result we propose to use the contrast in the integrated intensity of hydrogen lines to estimate the total energy flux of the bombarding beam during the solar flare impulsive phase. Partial frequency redistribution is considered in the Lyαline calculation and a smaller intensity enhancement in the Ha line-centers is found than in the previous results of Fang et al.