太阳黑子本影振荡的多波段观测

基于多波段的观测数据, 研究了黑子本影振荡在太阳大气不同高度或温度的振荡特征. 目标黑子发生在2017年9月15日, 位于活动区12680. 多波段的观测数据包括AIA (Atmospheric Imaging Assembly)的极紫外成像及IRIS (Interface Region Imaging Spectrograph)的紫外光谱和成像. 在太阳黑子的本影位置, AIA 1700 Å 光变曲线的振荡周期约为(4.2士0.8) min,而AIA 1600 Å、171 Å和193 Å光变曲线的振荡周期约为(2.8士0.3)min. IRIS的Mg II h和k谱线及远紫外成像(2796 Å)都表现为(3.1士0.5) min的准周期振荡,而谱线Si IV 1393.76 Å的振荡周期约为(2.9+0.4)min.观测结果说明黑子本影的振荡周期随着太阳大气高度的升高而逐渐减小.较短的周期可认为是3 min振荡,很可能与黑子本影上方的慢磁声波有关,它起源于温度极小区并向上传播到日冕.较长的周期可解释为光球的5 min振荡,与太阳的P模振荡有关.     

冕环振荡的物理特征研究

太阳动力学观测站(Solar Dynamics Observatory,SDO)上的太阳大气成像仪(Atmospheric Imaging Assembly,AIA)利用谱线Fe IX 171 (A)在2010年10月16日对整个日面进行了连续的高分辨率观测,获得了高质量的数据.这些高质量的数据提供了仔细研究冕环振荡的样本.通过分析这份数据,发现活动区NOAA 1112在此期间爆发了一个M2.9级的耀斑.该耀斑触发了太阳表面的多个冕环产生强烈振荡.其中最为明显的两个振荡冕环呈现出截然不同的振荡特征.位于西492 Mm,南170 Mm(简称W492/S170,后面出现的坐标位置均采取这种标注)处的冕环做周期为pA0 =385 s的简谐振荡,其振荡方程为x=2.2sin[2π55(t-768)],其中t为时间,单位为s;而位于W559/S142处的冕环则是一种典型的阻尼振荡,其阻尼振荡周期为Pf =449 s,相应的振荡方程可表示为x=24.8e-2π/342tsin[2π/449(t-1128)].     

卫星黑子衰减触发的喷流事件

详细分析了一次太阳低层大气磁场重联触发的喷流事件.这次喷流发生在2014年8月1日,爆发自美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration, NOAA)活动区12127边缘的一个卫星黑子处.该喷流爆发包括日浪、紫外喷流、极紫外高温和低温喷流.大熊湖太阳天文台(Big Bear Solar Observatory,BBSO)的Goode Solar Telescope (GST)高分辨率氧化钛(TiO)谱线的光球观测显示,喷流爆发过程中,卫星黑子一直衰减.到喷流结束,卫星黑子面积共减少了80%.在此过程中,太阳动力学天文台(Solar Dynamics Observatory, SDO)日球磁场成像仪(Helioseismic and Magnetic Imager, HMI)的视向磁场观测表明,该卫星黑子对应的负极磁场与相邻的正极磁场发生明显对消,产生喷流足部亮点.根据SDO卫星太阳大气成像仪(Atmospheric Imaging Assembly, AIA)的多波段观测,该足部亮点首先出现在紫外1600?波段.待紫外(1600?)喷流从紫外足部亮点顶部向上喷发,在极紫外波段也观测到相应的亮源.随着足点源亮度突然增强,有明显的极紫外低温喷流和日浪从足部亮点侧面喷发.从GST的高分辨率Hα图像上,可见日浪由许多精细纤维组成,这些纤维扎根在足点源的东南侧.根据从光球层过色球层再到日冕层的多波段高分辨率观测,色球中下层的磁场对消触发了这次喷流事件.向上喷发的物质流可以携带能量进入上层大气,并加热上层大气.研究结果表明,低层大气磁重联可能对解决日冕加热问题起重要作用.     

对2007年5月23日的一个CME的起源和初始阶段的观测研究

利用多波段联合观测数据,综合分析研究了一个发生于2007年5月23日的日冕物质抛射(Coronal Mass Ejection,CME)爆发事件的起源和初始阶段的物理演化过程.该CME起源于活动区10956内的一个并没有严格地位于活动区极性反转线上的U形活动区暗条,该暗条首先被扰动,然后从中间部分开始缓慢上升.在暗条上升运动过程中,从极紫外和软X射线像上可观测到位于暗条上方的日冕磁环也在不断地上升并且有持续向外的扩张运动.最终,这些冕环和暗条一起爆发并伴随着一个位于暗条断开位置附近的日冕暗化区域的形成.这一爆发过程还伴随着一个静止轨道业务卫星(GeostationaryOperational Environmental Satellites,GOES)软X射线流量级别为B5.3的亚耀斑发生,该光斑显示出与CME之间具有在时间和空间上的紧密联系.与CME的"标准"磁流绳模型一致,这些太阳表面活动可以看作是CME的初始演化阶段在日面上的表现信号,并且该CME的亮前锋可能是由预先存在于暗条上方的冕环体系直接演化而来.另外,文中还讨论了与该事件相关的暗条爆发、耀斑、冕环扩张和消失以及日冕暗化之间的关系.     

旋涡黑子在1972年10月太阳活动中的作用

本文收集了云南天文台和北京天文台观测的1972年10月太阳活动区(McMath 12094)的68个耀斑192个节点的照相资料和一些黑子日珥形态,对它们进行了相关分折,得到如下主要结果:1.本区最初的耀斑活动开始于全群诸黑子中具有扭结磁场最高能态的前导黑子A(N)的上空,它迅速发展到后随S极黑子上空,然后发展到黑子面积以外.这一演变过程与全群黑子的形态变化和旋转运动同步.2.A黑子附近的耀斑活动最初开始于扭结磁力管的内部,与扭结磁形态的松解过程同步,耀斑节点的分布由黑子本影附近移向半影的外面.当扭结完全松开,该处耀斑活动全面减少.3.发现了一个巨大的黑子冕珥下面的强烈的吸引中心是旋涡黑子,从而证实了冕珥是强大电流在日冕中收缩形成的.4.对于A黑子的扭转磁结构提供了本区耀斑活动的主要能量来源和导致不稳定性的问题进行了讨论.     

黑子半影内偶极运动磁特征的Hinode观测研究

利用Hinode卫星观测的单色像和磁图,对出现在黑子半影内的35对偶极运动磁特征进行形态特征、运动速度以及低层太阳大气响应3方面的研究,得出以下结论:(1)偶极运动磁特征正负两极成对出现在黑子半影较垂直的磁场之间并向着半影外边界运动,间接验证了偶极运动磁特征起源于黑子半影水平磁场,在2-8小时的时间间隔内,同一位置上会反复出现形态特征和运动速度相似的偶极运动磁特征,为海蛇状磁力线模型提供了证据支持. (2)光球和色球在偶极运动磁特征向外运动过程中会出现增亮,说明偶极运动磁特征会加热中低层太阳大气.(3)偶极运动磁特征的出现位置和半影磁场结构分布符合非梳子状黑子半影结构特征.     

旋涡黑子在1972年10月太阳活动中的作用

本文收集了云南天文台和北京天文台观测的McMath 12094活动区的68个耀斑192个节点的照像资料和一些黑子日珥形态,它们和黑子精细结构形态的相关分析进一步证实了过去的结论(7.8)。 1、本区最初耀斑活动开始于全群诸黑子中具有扭结磁场最高能态的前导黑子A(N)的上空,它迅动发展到后随S极黑子上空,然后发展到黑子面积以外。这一演化过程与全群黑子的形态变化和旋转运动同步。 2、巨大的A黑子附近的耀斑活动最初开始扭结磁力管的内部,与扭结磁形态的松解过程同步,耀斑节点的分布由黑子本影附近移向半影的外面。当扭结完全松开,该处耀斑活动全面减少。 3、发现了一个巨大的黑子冕珥下面的强烈的吸引力中心是旋涡黑子。从而证实了冕珥是强大电流在日冕中收缩形成的。 4、对于A黑子的扭转磁结构提供了本区耀斑活动的主要能量来源和导致不稳定性的问题进行了讨论。     

2003年10月22日太阳活动区AR0484内日浪事件的研究

利用色球Hα、TRACE／WL、SOHO／EITEuV单色像观测资料及SOHO／MDI光球磁场观测资料，对2003年10月22日太阳活动区AR0484内发生的日浪事件进行了研究．发现：(1)在Ha线心观测上，日浪包含有亮、暗2个分量，这2个分量先后出现而且并不共空间．日浪的亮分量与UV和EUV波段上观测到的喷发具有较好的同时性和共空间性．(2)日浪喷发物质沿着EUV环运动。(3)在光球层，日浪足根处的黑子和磁场有明显的变化．这些观测结果支持日浪的磁重联模型。     

基于相位一致性和方向滤波冕环震荡识别与跟踪

冕环结构的准确识别和跟踪有利于更好地研究和分析冕环特征以及同耀斑爆发和日冕物质抛射之间的关系。提出基于相位一致性和方向滤波的冕环震荡识别和跟踪方法。识别过程如下:首先,使用相位一致性技术对太阳图像中的冕环特征进行识别;其次,对识别后的图像进行二值化处理;接着使用方向滤波去除非冕环的结构特征;然后,对其进行形态学处理;最后,再对识别结果进行二次曲线拟合。运用所提算法对2011年9月6日由太阳动力学观测站(Solar Dynamics Observatory,SDO)在Fe IX 17.1 nm波段观测到的冕环震荡进行了识别和跟踪,结果验证了所提算法的可行性和准确性。证明所提算法能被用于冕环特性以及震荡过程的研究和分析。     

太阳日冕加热事件的多波段分析

随着大熊湖太阳天文台的1.6 m口径的新太阳望远镜(BBSO/NST)的成功运行,太阳观测已经进入了优于O.1″的高分辨率时代.这有助于详细分析单个曰冕加热事件,从而为日冕加热问题的最终解决提供原始的高分辨率的观测证据.利用NST所获得的在中性氦10830 A谱线、氧化钛7057 A谱线和H_α蓝翼(-0.7A)高分辨率成像观测数据,结合太阳动力学天文台上搭载的大气成像仪(SDO/AIA)和曰球磁场成像仪(SDO/HMI)同时观测到的极紫外和纵向磁场成像数据,分析了源自太阳米粒间通道的两个小的曰冕加热事件(磁环增亮)中的磁场演化.发现:这两个增亮磁环的足点都处于磁场中性线附近的一侧,一个磁环的足点伴随着一个小的纵向磁场单元的消失和两个米粒之间新形成的连接;在另一磁环的足点伴随着纵向磁场的微弱变化和一个米粒的破碎.据此,倾向于认为发生在太阳米粒之间底层大气的重联同时产生了高温和低温物质的外流.同时指出高分辨率和高偏振测量精度的光球磁场观测对于最终解决曰冕加热问题是至关重要的.     

On the origin of the solar system and the exceptional position of the Sun in the Galaxy

The solar system's position in the Galaxy is an exclusive one, since the Sun is close to the corotation circle, which is the place where the angular velocity of the galactic differential rotation is equal to that of density waves displaying as spiral arms. Each galaxy contains only one corotation circle; therefore, it is an exceptional place. In the Galaxy, the deviation of the Sun from the corotation is very small — it is equal to ΔR/R _⊙≈0.03, where ΔR=R _c ?R _⊙,R _c is the corotation distance from the galactic center andR _⊙ is the Sun's distance from the galactic center. The special conditions of the Sun's position in the Galaxy explain the origin of the fundamental cosmogony timescalesT ₁≈4.6×10⁹ yr,T ₂?10⁸ yr,T ₃?10⁶ yr detected by the radioactive decay of various nuclides. The timescaleT ₁ (the solar system's ‘lifetime’) is the protosolar cloud lifetime in a space between the galactic spiral arms. The timescaleT ₂ is the presolar cloud lifetime in a spiral arm.T ₃ is a timescale of hydrodynamical processes of a cloud-wave interaction. The possibility of the natural explanation of the cosmogony timescales by the unified process (on condition that the Sun is near the state of corotation) can become an argument in favour of the fact that the nearness to the corotation is necessary for the formation of systems similar to the Solar system. If the special position of the Sun is not incidental, then the corotation circles of our Galaxy, as well as those of other galaxies, are just regions where situations similar to ours are likely to be found.     

Perturbations by the oblateness of the Earth and by the planets in the motion of the Moon

Perturbations in the motion of the Moon are computed for the effect by the oblateness of the Earth and for the indirect effect of planets. Based on Delaunay's analytical solution of the main problem, the computations are performed by a method of Fourier series operation. The effect of the oblateness of the Earth is obtained to the second order, partly adopting an analytical evaluation. Both in longitude and latitude are found a few terms whose coefficient differs from the current lunar ephemeris based on Brown's theory by about 0.01. While, concerning the indirect effect of planets, several periodic terms in the current ephemeris seem to have errors reaching 0.05.As for the secular variations of and due to the figure of the Earth and the indirect effect of planets, the newly-computed values agree within 1/cy with Brown's results reduced to the same values of the parameters. Further, the accelerations in the mean longitude, and caused by the secular changes in the eccentricity of the Earth's orbite and in the obliquity of the ecliptic are obtained. The comparison with Brown shows an agreement within 0.3/cy² for the former cause and 0.02/cy² for the latter. An error is found in the argument of the principal term for the perturbations due to the ecliptic motion in the current ephemeris.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980.     

On the theory of the oblateness of the Sun

In this paper we first emphasize why it is important to know the successive zonal harmonics of the Sun's figure with high accuracy: mainly fundamental astrometry, helioseismology, planetary motions and relativistic effects. Then we briefly comment why the Sun appears oblate, going back to primitive definitions in order to underline some discrepancies in theories and to emphasize again the relevant hypotheses. We propose a new theoretical approach entirely based on an expansion in terms of Legendre's functions, including the differential rotation of the Sun at the surface. This permits linking the two first spherical harmonic coefficients (J ₂ and J ₄) with the geometric parameters that can be measured on the Sun (equatorial and polar radii). We emphasize the difficulties in inferring gravitational oblateness from visual measurements of the geometric oblateness, and more generally a dynamical flattening. Results are given for different observed rotational laws. It is shown that the surface oblateness is surely upper bounded by 11 milliarcsecond. As a consequence of the observed surface and sub-surface differential rotation laws, we deduce a measure of the two first gravitational harmonics, the quadrupole and the octopole moment of the Sun: J ₂=−(6.13±2.52)×10⁻⁷ if all observed data are taken into account, and respectively, J ₂=−(6.84±3.75)×10⁻⁷ if only sunspot data are considered, and J ₂=−(3.49±1.86)×10⁻⁷ in the case of helioseismic data alone. The value deduced from all available data for the octopole is: J ₄=(2.8±2.1)×10⁻¹². These values are compared to some others found in the literature. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005238718479     

On the model of the accumulation of the moon compatible with the data on the composition and the age of lunar rocks

It is suggested that the overall early melting of the lunar surface is not necessary for the explanation of facts and that the structure of highlands is more complicated than a solidified anorthositic ‘plot’. The early heating of the interior of the Moon up to 1000K is really needed for the subsequent thermal history with the maximum melting 3.5 × 10⁹ yr ago, to give the observed ages for mare basalts. This may be considered as an indication that the Moon during the accumulation retained a portion of its gravitational energy converted into heat, which may occur only at rapid processes. A rapid (t < 10³ yr) accretion of the Moon from the circumterrestrial swarm of small particles would give necessary temperature, but it is not compatible with the characteristic time 10⁸ yr of the replenishment of this swarm which is the same as the time-scale of the accumulation of the Earth. It is shown that there were conditions in the circumterrestial swarm for the formation at a first stage of a few large protomoons. Their number and position is evaluated from the simple formal laws of the growth of satellites in the vicinity of a planet. Such ‘systems’ of protomoons are compared with the observed multiple systems, and the conclusion is reached that there could have been not more than 2–3 large protomoons with the Earth. The tidal evolution of protomoon orbits was short not only for the present value of the tidal phase-lag but also for a considerably smaller value. The coalescence of protomoons into a single Moon had to occur before the formation of the observed relief on the Moon. If we accept the age 3.9 × 10⁹ yr for the excavation of the Imbrium basin and ascribe the latter to the impact of an Earth satellite, this collision had to be roughly at 30R, whereR is the radius of the Earth, because the Moon at that time had to be somewhere at this distance. Therefore, the protomoons had to be orbiting inside 20–25R, and their coalescence had to occur more than 4.0x10⁹ yr ago. The energy release at coalescence is equivalent to several hundred degrees and even 1000 K. The process is very rapid (of the order of one hour). Therefore, the model is valid for the initial conditions of the Moon.     

Accounting for the viscosity of the fluid core in the problem of the physical libration of the moon

A two-component theoretical model of the physical libration of the Moon in longitude is constructed with account taken of the viscosity of the core. In the new version, a hydrodynamic problem of motion of a fluid filling a solid rotating shell is solved. It is found that surfaces of equal angular velocity are spherical, and a velocity field of the fluid core of the Moon is described by elementary functions. A distribution of the internal pressure in the core is found. An angular momentum exchange between the fluid core and solid mantle is described by a third-order differential equation with a right-hand side. The roots of a characteristic equation are studied and the stability of rotation is proved. A libration angle as a function of time is found using the derived solution of the differential equation. Limiting cases of infinitely large and infinitely small viscosity are considered and an effect of lag of a libration phase from a phase of action of an external moment of forces is ascertained. This makes it possible to estimate the viscosity and sizes of the lunar fluid core from data of observations.     

On some problems concerning the calculation of the form of the magnetopause and the electric field on the magnetopause in the framework of the continuum medium model

In order to understand the reason of the existence of the electric field in the magnetosphere, and for the theoretical evaluation of its value, it is necessary to find the solution of the problem of determination of the magnetosphere boundary form in the frameworks of the continuum medium model which takes into account part of the magnetospheric plasma movement in supporting the magnetospheric boundary equilibrium. A number of problems for finding the distribution of the pressure, the density, the magnetic field and the electric field on the particular tangential discontinuity is considered in the case when the form of discontinuity is set (the direct problem) and a number of problems for finding the form of the discontinuity and the distribution of the above-mentioned physical quantities on the discontinuity is considered when the law of the change of the external pressure along the boundary is set (for example, with the help of the approximate Newton equation). The problem which is considered here, which deals with the calculation of the boundary form and with the calculation of the distribution of the corresponding physical quantities on the discontinuity of the 1st kind for the compressible fluid with the magnetic field with field lines which are perpendicular to the plane of the flow in question, concerns the last sort of problems. The comparison of the results of the calculation with the data in the equatorial cross-section of the magnetosphere demonstrates that the calculated form of the boundary, the value of the velocity of the return flow and the value of the electric field on the magnetopause, agree satisfactorily with the observational data.     

Third Integral and the Dynamics of the Galaxy in the Neighborhood of the Sun

Observational data on the dynamics of stars in the neighborhood of the sun indicate the existence of a third integral besides the integrals of the angular momentum and energy. The Poincaré integral is proposed as a third integral. The consequences of this assumption are derived and compared with available astrophysical data.