两冕流间物质抛射事件的数值模拟

二维磁流体力学方程数值敢两冕流间的日冕物质抛射事件。为了能重现两冕流间ＣＭＥ的基本特征,本文在加入一定强度的扰动热压的同时,叠加了一个由圆线电流产生的闭合磁场。模拟结果表明,此类扰动能形成明显的高密度等离子体环形结构,且外环后随一暗脸。它们在径向和横向 都存在不同程度的膨胀。     

日冕物质抛射在太阳活动周期内的变化

本文利用SMM1980年和1984年观测的两组日冕物质抛射事件(CMF)及同期耀斑和爆发日珥观测资料,从速度、位置及活动相关率三个方面分析CME在这两个不同时期的特征,并由此推测它在整个太阳活动周内的变化趋势.     

日冕物质抛射中非对称高密度云和非线性波的形成和演化

应用函数拟合及数字滤波等方法,对SMM飞船观测的1980年8月18日日冕物质抛射事件进行了定量分析。论证了不对称高密度云的形成与爆发日珥顶端偏离冕流对称轴有关,讨论了此不对称结构的演化及其对事件发展的影响,作出了暗腔是强磁场膨胀体的重要论断。从图象亮度的高度分布剖面中,分析出日冕非线性波在演化过程中前沿变陡的观测证据,推算了演化成激波的时间和高度,并论证了两者都是强磁场膨胀体所驱动的,而不是瞬时能量爆发所引起的。     

扭转Alfvén波共振的数学描述

提出完备正交函数基(OFSE)展开方法,求解冕环中无耗散扭转Alfvn波。每个基函数对应冕环中每根磁力线的一个固有角频率ω_n,当冕环足点驱动频率等于磁力线的固有频率时,Alfvn波将在这根磁力线处发生共振。采用OFSE方法求解了双足点驱动时冕环Alfvn波的时变演化问题,给出了时变解析解的新形式,其中包含共振项,从共振项可以发现,在共振角频率为ω的共振磁力线附近,在时间t为π/ω的整数倍时,出现δ型间断;在t为π/(2ω)的奇数倍时,出现1/x间断。共振磁力线振幅随时间线性增加,增加的斜率正比于Alfvn波速,反比于冕环长度,与驱动频率无关。     

Helios飞船观测到的行星际日冕物质抛射事件

根据异常低的质子温度判据,从Helios 1和2飞船等离子体观测数据中（0.3-1 AU）识别出大约160个行星际日冕物质抛射事件（ICME）,并在统计意义上分析了ICME在内日球空间的传播和演化规律.     

两冕流间的对称径向膨胀日冕物质抛射事件

本文讨论了发生在冕流对之间的1980年5月6日日冕物质抛射事件。提出了一种描述事件外环运动的经验模型,把环的观测外形表达为在运动坐标系中的Cassini函数。环的发展过程分为两个阶段:在前一阶段,外环处于冕流对盔状结构之间,事件的发展以角宽度膨胀为主,其对称轴从赤道向北纬方向移动;径向膨胀和上升速度较低,加速效应明显。在后一阶段,外环越过冕流盔状结构所在高度,角膨胀趋于停止;运动接近于等角宽度和纯径向匀速的膨胀和上升运动。当外环向外运动时,其顶部和几何中心的高度均随时间而增加,但其底部高度基本上保持不变。根据上述观测特征,讨论了事件形成的可能机制。     

1998年5月日冕三维结构的数值模拟

采用三维理想磙流体力学（MHD）模式，内边界条件把二维投影特征线边界方法推广应用到三维计算，有效地稳定了数值计算并保证稳态解的自洽性；初始猜解磁场由1935卡林顿周光球磁场观测数据得到，这样计算得到的1998年5月份期间日冕三维结构比较符合实际，计算结果表明：（1）计算得到的源表面非径向磁场量值在磁中性线附近不超过2μT，表明源表面磁场基本径向。（2）模拟得到的源表面径向磁场量值除了在磁中性线附近的区域外变化不大，这和观测一致。（3）由源表面磁场按平方反比的规律计算出1AU处磁场量值更接近观测值。（4）计算得到的日冕结构和观测定性一致，三维数值模拟结果表明，日冕的三维大尺度背景结构主要是由磁场决定的，在闭磁场处或者电流片附近，太阳风的密度高，速度低；在开场区，太阳风的密度低，速度高。     

子午面太阳风结构及其对日冕抛射物运动的影响

本文提出了一种求解二维理想磁流体力学方程组的组合格式-网格方法。该方法在保证一定精度的前提下稳定性好,计算量小。文中使用该方法算得了子午面太阳风的盔状流动解。以该解作为初态,研究了盔状冕旒位形对日冕抛射物运动的影响,发现该位形使得抛射物向低纬赤道方向偏转,较好地解释了观测结果。     

Spectral analysis of 3D MHD models of coronal structures

We study extreme-ultraviolet emission line spectra derived from three-dimensional magnetohydrodynamic models of structures in the corona. In order to investigate the effects of increased magnetic activity at photospheric levels in a numerical experiment, a much higher magnetic flux density is applied at the photosphere as compared to the Sun. Thus, we can expect our results to highlight the differences between the Sun and more active, but still solar-like stars. We discuss signatures seen in extreme-ultraviolet emission lines synthesized from these models and compare them to observed signatures in the spatial distribution and temporal evolution of Doppler shifts in lines formed in the transition region and corona. This is of major interest to test the quality of the underlying magnetohydrodynamic model to heat the corona, i.e. currents in the corona driven by photospheric motions (flux braiding).     

Kuafu and the studies of CME initiation

We first briefly review the current trend in the studies of coronal mass ejections (CMEs), then summarize some recent efforts in understanding the CME initiation. Emphasis has been put on the studies of Earth-directed CMEs whose associated surface activity and large scale magnetic source have been well identified. The data analysis by combining the MDI full disc magnetograms, vector magnetograms of active regions, EUV waves and dimmings, non-thermal radio sources, and the SOHO LASCO observations has shed new light in understanding the CME magnetism. However, the current studies seem to invoke new observations in a few aspects: (1) The observations which enable us to trace CMEs from the earliest associated surface activity to its initial acceleration and key development in the low corona in the height of 1–3 R; (2) The imaging spectroscopic observations which can be used to diagnose the early plasma outflow and the line-of-sight velocity in understanding the kinematics of CMEs; (3) The accurate timing from primary magnetic energy release, manifested by chromospheric activity, non-thermal radio bursts, and EUV, X-ray and γ-ray emissions, to the CME initiation, early acceleration and propagation, and the consequences in the interplanetary space and magnetosphere. The Kuafu Mission will meet the basic requirement for the new observations in CME initiation studies and serve as a monitor of space weather of the Sun–Earth system.     

Characterization of the slow wind in the outer corona

The study concerns the streamer belt observed at high spectral resolution during the minimum of solar cycle 23 with the Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO. On the basis of a spectroscopic analysis of the O VI doublet, the solar wind plasma parameters are inferred in the extended corona. The analysis accounts for the coronal magnetic topology, extrapolated through a 3D magneto-hydrodynamic model, in order to define the streamer boundary and to analyse the edges of coronal holes. The results of the analysis allow an accurate identification of the source regions of the slow coronal wind that are confirmed to be along the streamer boundary in the open magnetic field region.     

Highlights of the Brazilian Solar Spectroscope

The digital, decimetric (950–2500 MHz) Brazilian Solar Spectroscope (BSS, Sawant, H.S., Subramanian, K.R., Faria, C., et al. Brazilian Solar Spectroscope (BSS). Solar Phys. 200, 167–176, 2001) with high time (10–1000 ms) and frequency (1–10 MHz) resolution is in regular operation since April, 1998, at the National Space Research Institute (INPE) at São José dos Campos, Brazil. The BSS has now been upgraded with a new digital data acquisition and data processing system. The new version of the BSS has improved the observational possibilities with the capability to record up to 200 frequency channels available in the selectable frequency range 950–2500 MHz. The GPS receiver permits the acquisition of data with time accuracy in the order of 0.1 ms. The software system of the BSS is composed by two distinct modules: the first, data acquisition system provides a flexible Graphical User Interface (GUI) that allows one to choose the observational parameters. The second module is the real time visualization system that permits real time visualization of the observed dynamic spectrum and additionally allows procedures for visualization and preliminary analysis of the recorded solar spectra. Using the new visualization system, we have realized two new types of dm-radio fine structures: narrow band type III bursts with positive as well as negative group frequency drift and dots emissions arranged in zebra-like and fiber-like chains. Furthermore, we have found flare generated fast wave trains according to their tadpole signature in wavelet power spectra for a decimetric type IV radio event (June 6, 2000 flare).     

Study of a Coronal Mass Ejection with SOHO/UVCS and STEREO data

We study the 3-D kinematics of a Coronal Mass Ejection (CME) using data acquired by the LASCO C2 and UVCS instruments on board SOHO, and the COR1 coronagraphs and EUVI telescopes on board STEREO. The event, which occurred on May 20, 2007, was a partial-halo CME associated with a prominence eruption. This is the first CME studied with UVCS data that occurred in the STEREO era. The longitudinal angle between the STEREO spacecrafts was ∼7.7° at that time, and this allowed us to reconstruct via triangulation technique the 3-D trajectory of the erupting prominence observed by STEREO/EUVI. Information on the 3-D expansion of the CME provided by STEREO/COR1 data have been combined with spectroscopic observations by SOHO/UVCS. First results presented here show that line-of-sight velocities derived from spectroscopic data are not fully in agreement with those previously derived via triangulation technique, thus pointing out possible limitations of this technique.     

On the nature of coronal loops above the quiet sun network

The structure and dynamics of a box in a stellar corona can be modeled employing a 3D MHD model for different levels of magnetic activity. Depending on the magnetic flux through the surface the nature of the resulting coronal structures can be quite different. We investigate a model of an active region for two sunspots surrounded by magnetic field patches comparable in magnetic flux to the sunspots. The model results in emission from the model corona being concentrated in loop structures. In Gudiksen and Nordlund (2005) the loops seen in EUV and X-ray emission outline the magnetic field, following the general paradigm. However, in our model, where the magnetic field is far from a force-free state, the loops seen in X-ray emission do not follow the magnetic field lines. This result is of interest especially for loops as found in areas where the magnetic field emerging from active regions interacts with the surrounding network.     

CMEs and active regions on the sun

The relationship between active regions (ARs) and coronal mass ejections (CMEs) is studied. For this purpose a statistical analysis of 694 CMEs associated with ARs was carried out. We considered the relationship between properties of the CMEs and ARs characterized using the McIntosh classification. We demonstrated that CMEs are likely to be launched from ARs in the mature phase of their evolution when they have complex magnetic field. The fastest and halo CMEs can be ejected only from the most complex ARs (when an AR is a bipolar group of spots with large asymmetric penumbras around the main spot with many smaller spots in the group). We also showed that the wider events have a tendency to originate from uncomplicated magnetic structures. This tendency was used for estimation of the real angular widths of the halo CMEs. The probability of launching of fast CMEs increases together with increase of the complexity and size of ARs. The widest, but slow, CMEs originate from the simplest magnetic structure which are still able to produce CMEs. Our results could be useful for forecasting of space weather.     

非真空收集器质谱检漏技术

叙述了一种经济实用的被检件在非真空收集器中的质谱检漏方法,通过试验验证了方法的正确性,并从理论上分析了漏率的标定方法、检漏灵敏度以及检测误差。     

Coronal fast wave trains of the decimetric type IV radio event observed during the decay phase of the June 6, 2000 flare

The 22 min long decimetric type IV radio event observed during the decay phase of the June 6, 2000 flare simultaneously by the Brazilian Solar Spectroscope (BSS) and the Ond?ejov radiospectrograph in frequency range 1200–4500 MHz has been analyzed. We have found that the characteristic periods of about 60 s belong to the long-period spectral component of the fast wave trains with a tadpole pattern in their wavelet power spectra. We have detected these trains in the whole frequency range 1200–4500 MHz. The behavior of individual wave trains at lower frequencies is different from that at higher frequencies. These individual wave trains have some common as well as different properties. In this paper, we focus on two examples of wave trains in a loop segment and the main statistical parameters in their wavelet power and global spectra are studied and discussed.     

高频Alfven波供能的日冕及太阳风模型

空间探测的最新结果表明，太阳大气中广泛存在小尺度喷发事件，这些事件被认为是由新浮现磁通量导致的小尺度磁重联的表现．小尺度磁重联同时会产生高频Alfven波．本文给出了建立在上述思想基础上的描述日冕加热及太阳风加速的时变二元流体模型的一组数值解，显示解的时间演化、收敛特性及守恒特性．在对由过渡区发出的高频Alfven波频谱的适当假设下，数值解能够解释日冕及太阳风等多方面的观测结果，包括日冕加热，极冕洞密度径向变化，太阳风近日冕底部加速，及在03AU观测到的高速流特征．     

一种极化敏感反射器用的展开机构

极化敏感反射器用的展开机构由一对相同的展开铰链及一个调速器组成，每个铰链都有提供动力的扭转弹簧及闭锁装置；调速器通过一个绳轮和展开轴连接。调速器中以１６４倍于展开轴转速旋转的离心盘提出阻尼力矩，以稳定展开速度，防止冲击过大，并保证较高的展开重精度。机构通过了包括振动，真空热循环等鉴定试验。在真空中高温５２．３℃下的展开速度比－２０℃下高１４％，常温常压下在模拟零重力试验设备上测得的展开重复精度优于     

Three-dimensional global simulation of multiple ICMEs’ interaction and propagation from the Sun to the heliosphere following the 25–28 October 2003 solar events

This study performs simulations of interplanetary coronal mass ejection (ICME) propagation in a realistic three-dimensional (3D) solar wind structure from the Sun to the Earth by using the newly developed hybrid code, HAFv.2+3DMHD. This model combines two simulation codes, Hakamada–Akasofu–Fry code version 2 (HAFv.2) and a fully 3D, time-dependent MHD simulation code. The solar wind structure is simulated out to 0.08 AU (18 Rs) from source surface maps using the HAFv.2 code. The outputs at 0.08 AU are then used to provide inputs for the lower boundary, at that location, of the 3D MHD code to calculate solar wind and its evolution to 1 AU and beyond. A dynamic disturbance, mimicking a particular flare’s energy output, is delivered to this non-uniform structure to model the evolution and interplanetary propagation of ICMEs (including their shocks). We then show the interaction between two ICMEs and the dynamic process during the overtaking of one shock by the other. The results show that both CMEs and heliosphere current sheet/plasma sheet were deformed by interacting with each other.