1989年8月17日太阳边缘耀斑和速度场研究

本文利用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。通过分析比较，得出此耀斑环内物质运动可能属于下述两种模式：物质从环顶沿两环腿螺旋下落和物质从环足沿一环腿螺旋上升到环顶后沿另一腿螺旋下落     

圆面耀斑环物理量场的归算和分析

本文对云南天文台1981年5月16日3B级双带大耀斑环(0922UT)的H_α—SSHG光谱资料作了初步的数据处理。采用非线性函数的最小二乘曲线拟合方法,从光谱轮廓求得圆面耀斑环的线心光学厚度τ_0、Doppler宽度Δλ_D平均能源函数S_λ及视向速度V_(11)的二维分布,为处理具有时空序列的光谱资料提供了一种数值方法。计算结果表明,耀斑环系内的物质由环顶沿两环腿向色球层溅落;用色球蒸发模型解释环中的物质来源较为合理。     

1984年2月18日环状日珥和速度场

本文给出1984年2月18日耀斑后环的Hα色球和Hα-SSHG的光谱形态分析,同时给出它的二维视向速度场,并对该速度场特征给予定性解释。结果表明:(1)该环珥是一个耀斑后的拱廊(‘Post’-Flare Arch);(2)用环顶物质在重力和磁应力作用下主要沿光学厚环腿下落的假设能很好地解释观测结果。     

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。     

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     

两个大环状日珥群H_α单色光与光谱的同时观测

利用南京大学太阳塔,我们观测到1982年12月20日和1983年2月9日出现在日面西边缘的两个大环状日珥群。由同时获得的H_α单色光照相资料H_α、CallH·K线光谱资料测出了环内物质的视向速度分布,该分布与假定物质沿环无粘滞的自由下落推算出的视向速度分布相一致。利用H_α和K线的半宽求出了环内物质的运动温度及湍动速度,温度分布比较均匀,湍动速度随日面高度而增加。利用K线和H线线心强度之比,推算了环内物质的密度,得到氢原子密度为1.3—2.6×10~(10)cm~(-3),另外,还通过估算环珥群的总能量来讨论了环珥群与耀斑的关系。     

1981年4月27日耀斑环珥的H_α光谱太阳分光照像

云南天文台摄取1981年4月27日太阳西边缘的一个耀斑环珥的H_α光谱太阳分光照像(S~2HG)和H_α色球照像等资料。这些资料揭示了该耀斑环在爆发上升过程中内部运动和宏观运动随时空分布的大致图象: 1.亮度极大前耀斑环南腿系出现右螺旋运动,亮度极大后发展为两腿系的同向旋转运动,角速度约为4×10~(-3)弧度/秒。 2。两环腿的旋转角速度随腿的高度增加而减小。 3.南腿系的旋转跟它下面的N极主黑子的旋转方向一致,表明两者之间可能存在着某种内在的联系。 4.两环腿的同向旋转使环顶部的磁绳不断扭紧,导致Kink不稳定性的迅速发展,它可能是引起环顶瓦解的主要原因。 5.环顶部的H_α辐射强度和它的谱线宽度均大于两腿系,表明那里的某些物理量如N_3/N_2,n_e,T,v_t,等可能大于环腿对应的各物理量,环顶部是最不稳定的地方。     

太阳耀斑亮核和硬X射线环顶源运动的初步分析

分析了2个耀斑事件。这2个耀斑事件都具有双带结构，并伴有耀斑环顶部位置的硬X射线（HXR）辐射，这个辐射源我们称为环顶源。在文章中，通过求亮度重心的方法，我们对耀斑双带的相对运动，以及HXR环顶源的高度变化进行了分析。结果表明：耀斑相偶亮核间距离的时间曲线，与HXR亮度曲线具有相反的相关性，亮核间距离在HXR流量上升阶段会减少；与此同时，HXR环顶源的高度会下降。而通常的相偶亮核的分离运动以及环顶源的上升运动发生在极大相之后。     

1984年2月18日环珥系速度场的定量计算

本文研究了在太阳重力、偶极磁压强梯度和气体压力梯度力共同作用下环珥系内物质的下落运动,并在等温、准封闭环假设下用数值方法给出了该环珥系二维视向速度场。通过将速度场的理论计算跟观测结果拟合,导出了该环系内的有关物理参数及分布。计算表明环系内密度和磁场强度对物质下落运动的影响比较明显,而温度的影响较小。     

AR5629:1989年8月17日耀斑环的观测

利用怀柔太阳磁场望远镜,我们观测到1989年8月17日出现在太阳西边缘的耀斑环,它们产生在AR5629上(S17,L74)。当时,该活动区已转到日背面,约10°左右。17日,从UT0132至UT0911,我们取得了该耀斑环的一系列Hβ单色光资料(图1)和它们的二维实时视向速度场(图2)。从观测中,我们可以看到环的形成演化的全     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length to 6 printed pages).Authors who submit a paper are expected to be able to certify that the paper is original work,     

Research in Astronomy and Astrophysics CONTENTS

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Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews 011 all liranchcs of astronoiriy and astrophysics.Reviews arc by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length     

Alkali and halogen chemistry in volcanic gases on Io

We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10⁻⁶ to 10⁺¹ bars) ranges, which overlap the nominal conditions at Pele (T=1760 K, P=0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. The elemental abundances for O, S, Na, K, and Cl are based upon observations. CI chondritic elemental abundances relative to sulfur are used for the other alkalis and halogens (as yet unobserved on Io). We predict the major alkali species in Pele-like volcanic gases and the percentage distribution of each alkali are LiCl (73%), LiF (27%); NaCl (81%), Na (16%), NaF (3%); KCl (91%), K (5%), KF (4%); RbCl (93%), Rb (4%), RbF (3%); CsCl (92%), CsF (6%), Cs (2%). Likewise the major halogen species and the percentage distribution of each halogen are NaF (88%), KF (10%), LiF (2%); NaCl (89%), KCl (11%); NaBr (89%), KBr (10%), Br (1%); NaI (61%), I (30%), KI (9%). We predict the major halogen condensates and their condensation temperatures at P=0.01 bar are NaF (1115 K), LiF (970 K); NaCl (1050 K), KCl (950 K); KBr (750 K), RbBr (730 K), CsBr (645 K); and solid I₂ (200 K). We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. Their estimated photochemical lifetimes range from a few minutes for alkali iodides to a few hours for alkali fluorides. Condensation is apparently the only loss process for elemental iodine. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observations of brown dwarfs we also recommend a search of Io's extended atmosphere and the Io plasma torus for neutral and ionized Li, Cs, Rb, and F.     

The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts

Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr^− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.     

Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope.     

Active hot star shells

Interferometry in the visible provides milliarcsecond spatial resolution and thus has been used for studying the circumstellar environment of active hot stars. In this paper I will illustrate how the visibility modulus and phase can be used to better constrain the physics of Be disks through results from the VLA, the MkII and the GI2T interferometers. I will insist on the importance and the potential of coupling high angular resolution with high spectral resolution to the study of Be shells. Finally I will present a possible study of the circumstellar disk of Be stars using the VLTI. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fitting X-ray Afterglow Light curves of Gamma-ray Bursts by Using the Magnetar Energy Injection Model

The central compact object for some gamma-ray bursts (GRBs) may be a strongly magnetized millisecond pulsar. It can inject energy to the outer shock of the GRB by through the magnetic dipole radiation, and therefore causes the shallow decay of the early afterglow. Recently, from a large number of GRB X-ray afterglows observed by Swift/XRT(X-ray telescope), it is revealed that many of them exhibit the shallow decay about 10²∼10⁴ s after the burst prompt emission. We have fitted the X-ray afterglow light curves of 11 GRBs by using the energy injection model of a magnetar with the rotation period in the millisecond order of magnitude. The obtained result shows the validity and universality of the magnetar energy injection model in explaining the shallow decay of afterglows, and simultaneously provides some constraints on the magnetic field strength and rotation period of the central magnetar.     

我国新一代VLBI数字基带转换器研制进展

数字化是目前设备研制发展的趋势,介绍了中国科学院上海天文台利用超大规模集成电路结合软件无线电技术,自主研发的我国新一代VLBI数字基带转换器(Chinese Data Acquisition System,简称CDAS).文中描述了设备的工作原理及其组成,并以VLBI观测实验数据证明其可行性.与原有的模拟设备(Anal...