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1.
Hα谱线轮廓的不对称性是色球耀斑光谱观测中的重要特征,也是耀斑动力学过程的重要观测事实之一．以紫金山天文台太阳光谱仪的观测资料为依据,给出Hα谱线不对称性的典型轮廓．在考虑氢原子非热激发、电离的作用下,经验性地计算了不同大气模型下谱线的不对称性特征,并在此基础上,对观测谱线进行半经验的研究．结果表明, 色球区的向下运动能够产生Hα谱线的红、蓝不对称性,并可以再生具体耀斑的谱线不对称性特征．此外,不仅非热粒子的能流、谱指数大小以及速度场所处的高度对谱线轮廓有影响,耀斑大气的背景模型对谱线的轮廓也有一定的影响． 相似文献
2.
简要介绍了赖曼α森林的各种模型，宇宙流体力学模拟成功地再现了赖曼α森林的大部分观测结果，并使人们认识到：产生赖曼α森林的吸收体实际上是星系际介质中延伸的过密区，这种密度起伏是宇宙结构形成过程的自然结果。赖曼α森林己成为宇宙学研究的有力工具。 相似文献
3.
综述了近年来太阳色球耀斑爆发时Hα谱线不对称性的研究进展,着重讨论了光谱特征和与其对应的不对称性产生机制,以及利用大气半经验模型再生观测谱线轮廓不对称性等方面,并提出尚待解决的主要问题和进一步的研究方向。 相似文献
4.
5.
色球压缩区是耀斑大气动力学过程的一个基本特征，是产生色球谱线红不对称性的基础，本基于压缩区从大气高层向低层传播的理论公式，在二种不同情况下，计算得到了压缩区内物质运动速度随高度和时间的变化，结果表明，色球蒸发区压力增量△ｐ为常数时压缩区之寿命比压缩区波阵面后压力ｐ２为常数时要长得多，这就大大缓解了以往谱线不对称性的延续时间的理论值比观测值小的矛盾。形成高度不同的谱线具有不同程度的不对称性这一观测 相似文献
6.
色球压缩区是耀斑大气动力学过程的一个基本特征，是产生色球谱线红不对称性的基础。本文基于压缩区从大气高层向低层传播的理论公式，在二种不同情况下，计算得到了压缩区内物质运动速度随高度和时间的变化．结果表明，色球蒸发区压力增量Δｐ为常数时压缩区之寿命比压缩区波阵面后的压力ｐ２为常数时要长得多，这就大大缓解了以往谱线不对称性的延续时间的理论值比观测值小的矛盾。形成高度不同的谱线具有不同程度的不对称性这一观测现象也同色球压缩区的传播特性相一致。 相似文献
7.
本文介绍了高空间分辨率的太阳射电观测流量的归算方法，即对观测的太阳天线温度值作天线功率方向图Ｋ因子的修正，即可得到太阳射电流量值．文中推导了不同温度分布模型下的Ｋ因子表达式，并计算了日面宁静太阳流量值和部分射电源的ＳＶＣ辐射流量值．对日面宁静区的射电辐射而言，因Ｋ的年变化（０．０２３６—０．０２５２）不大，因此按其平均值０．０２４４可计算出２２ＧＨｚ频率上宁静太阳流量ｓ。＝０．１５Ｔａ。（以ｓｆｕ为单位，Ｔａ。是宁静区辐射的太阳天线温度），相应的宁静太阳温度为１０１００土３００Ｋ．１９９０年７月２日源区的ＳＶＣ辐射计算结果表明：日面源区的ＳＶＣ辐射总和为２０ｓｆｕ，约占日面总辐射的２．４％． 相似文献
8.
本分析了南京大学太阳塔１９９１年１０月２４日用多波段光谱仪观测到的高时间分辨率（５ｓ）的一个２Ｎ／Ｘ２．１级白光耀斑光谱，对耀斑谱线轮廓，连续发射强度，Ｘ射线和射电爆发资料进行了综合对比，分析表明，该耀斑属Ｉ类白光耀斑，具有如下特征：（１）在白光耀斑的脉冲相期间，各波段光谱线心强度，连续辐射，谱线半宽以及线翼红不对称性与硬Ｘ射线高能波段的爆分同时达到极大；（２）Ｈα谱线在连续发射极大时半宽达１０ 相似文献
9.
耀斑谱线轮廓的不对称性是耀斑动力学过程的一个重要观测事实。本文在一定的耀斑半经验大气模型基础上,计算了不同速度模式和色球凝聚下的Ha和CaⅡK谱线轮廓,从半经验角度探讨了大气各个层次的速度对Hα和CaⅡK谱线轮廓的影响。结果表明:耀斑早期短时间的Hα蓝不对称性可由位于过渡区的色球凝聚引起;随后的红不对称性是上部色球物质向下运动的结果;而后来出现的CaⅡK不对称性特征则可由色球中、下部具有10—20km/s的向下速度来解释。 相似文献
10.
以1988年9月5日北京天文台怀柔太阳观测站高分辨率和高灵敏度磁强图为基础,首次给出了对一太阳宁静区小尺度磁场空间分布的二维功率谱。 尽管从总体上,功率谱的分布呈现从低频分量向高频分量迅速衰减的趋势,但是,反映小尺度磁场分布的不同尺度空间周期性的分离的尖峰,是功率谱的最主要特征。 本文的主要结果可概括为下列两点: (1)太阳宁静区的磁通量不仅凝聚在分离的、具有相对较强磁通量密度的磁结构内,而且磁结构的空间分布也呈现分离的尺度不同的周期。 (2)小尺度磁场空间分布的最显著的周期,具有超米粒的空间尺度。这与以往磁对流理论与有关观测结果相一致。在功率谱中,还可以证认相应于亚超米粒,及亚超米粒和超米粒之间尺度的空间周期的大量尖峰。这是本文首次得到的。 包含更多观测资料的进一步工作是必须的,特别是获得对同一宁静区的速度场和磁场同时性的二维功率谱,对研究磁场和对流速度场的相互作用是有重要意义的。观测的功率谱与理论预测谱的比较,将有助于理解太阳光球分离磁结构形成的物理过程。 相似文献
11.
A large filament was observed during a multi-wavelength coordinated campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE) and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman series with the SOHO/SUMER spectrometer. Because of its high-latitude location, it is possible to disentangle the physical properties of the Hα filament and the filament channel seen in EUV lines. TRACE images point out a dark region fitting the Hα fine-structure threads and a dark corridor (filament channel), well extended south of the magnetic inversion line. A similar pattern is observed in the CDS EUV-line images. The opacity of the hydrogen and helium resonance continua at 171 Å is almost two orders of magnitude lower than that at the Hi head (912 Å) and thus similar to the opacity of the Hα line. Since we do not see the filament channel in Hα, this would imply that it should also be invisible in TRACE lines. Thus, the diffuse dark corridor is interpreted as due to the coronal ‘volume blocking’ by a cool plasma which extends to large altitudes. Such extensions were also confirmed by computing the heights from the projection geometry and by simulations of the CDS and TRACE line intensities using the spectroscopic model of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally, our NLTE analysis of selected hydrogen Lyman lines observed by SUMER also leads to a conclusion that the dark filament channel is due to a presence of relatively cool plasma having low densities and being distributed at altitudes reaching the Hα filament. 相似文献
12.
We present results from sunspot observations obtained by SUMER on SOHO. In sunspot plumes the EUV spectrum differs from the
quiet Sun; continua are observed with different slopes and intensities; emission lines from molecular hydrogen and many unidentified
species indicate unique plasma conditions above sunspots. Sunspot plumes are sites of systematic downflow. We also discuss
the properties of sunspot oscillations 相似文献
13.
Homogeneous plane-parallel model atmospheres for solar flares have been constructed to approximately simulate observations of flares. The wings of the Ca II lines have been used to derive flare upper photosphere models, which indicate temperature increases of ～100 K over the temperature distribution in the pre-existing facula at a height of 300 km above τ5000 = 1. In the case of flares covering sunspots the temperature rise seems to occur much higher in the atmosphere. We solve the transfer and statistical equilibrium equations for a three-level hydrogen atom and a five-level calcium atom in order to obtain the chromospheric flare models. The general properties of flares, including n e, N 2, linear thickness, and Lyman continuum intensity are approximately reproduced. We find that with increasing flare importance the height of the upper chromosphere and transition region occur lower in the solar atmosphere, accounting for the factor of 60–600 increase in pressure in these regions relative to the quiet Sun. The Ca II line profiles agree with observations only by assuming a macro-velocity distribution that increases with height. Also the chromospheric parts of flares appear to be highly inhomogeneous. We show that shock and particle heated flare models do not agree with the observations and propose a thermal response model for flares. In particular, it appears that heating in the photosphere is an essential aspect of flares. 相似文献
14.
On 21 September 1996, a filament close to an area of enhanced network was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer and Coronal Diagnostic Spectrometer (CDS). CDS provided intensity, Doppler shift and linewidth maps of the region in six lines whose temperature range covers 104 to 106 K. SUMER observations consisted of maps of the region in four hydrogen Lyman lines (L, L, L-6, L-7) and a Svi line (944 Å). In all the Lyman lines we detect a central absorption and an asymmetry in the intensity of the two peaks. First NLTE computations indicate that such reversed Lyman profiles and their absolute intensities can be reproduced with the existing filament models provided that we take into account a prominence-corona transition region (PCTR). We discuss the Lyman lines' asymmetry in terms of macroscopic flows by comparison with the Hei line Doppler shifts observed with CDS. 相似文献
15.
The hydrogen and helium lines are the most prominent lines in the solar prominences spectra. Observations with the SUMER spectrometer
onboard SOHO showed that there are weak lines in the blue wings of the Lyman series which affect their profiles. They were
all identified as He ii lines in the Lyman series wings, except for the Lα line whose profile was affected by the use of an attenuator. The He ii lines are the even Balmer lines of the He ii system, a set of lines that we complete with the odd ones. We characterize them by comparison with the blue wings of the
Lyman series in order to improve the H Lyman series observations and modeling, on one hand and to provide He ii lines observations for further combined H – He i – He ii modeling, on the other hand. 相似文献
16.
The spectral irradiance at the center of the solar H I Lyman α (, referred to as Lyα in this paper) line profile is the main excitation source responsible for the atomic hydrogen resonant scattering of cool material in our Solar System. It has therefore to be known with the best possible accuracy in order to model the various Lyα emissions taking place in planetary, cometary, and interplanetary environments. Since the only permanently monitored solar irradiance is the total one (i.e. integrated over the whole Lyα line profile), Vidal-Madjar [1975. Evolution of the solar Lyman alpha flux during four consecutive years. Solar Phys. 40, 69-86] using Orbiting Solar Observatory 5 (OSO-5) satellite Lyα data, established a semi-empirical formula allowing him to deduce the central spectral Lyα irradiance from the total one. This relation has been extensively used for three decades. But, at the low altitude of the OSO-5 orbit, the central part of the solar line profile was deeply absorbed by a large column of exospheric atomic hydrogen. Consequently, the spectral irradiance at the center of the line was obtained by a complex procedure confronting the observations with simulations of both the geocoronal absorption and the self-reversed shape of the solar Lyα profile. The SUMER spectrometer onboard SOHO positioned well outside the hydrogen geocorona, provided full-Sun Lyα profiles, not affected by such an absorption [Lemaire et al., 1998. Solar H I Lyman α full disk profile obtained with the SUMER/SOHO spectrometer. Astron. Astrophys. 334, 1095-1098; 2002. Variation of the full Sun Hydrogen Lyman α and β profiles with the activity cycle. Proc. SOHO 11 Symposium, ESA SP-508, 219-222; 2004. Variation of the full Sun Hydrogen Lyman profiles through solar cycle 23. COSPAR 2004 Meeting], making it—for the first time—possible to measure the spectral and total Lyα solar irradiances directly and simultaneously. A new relation between these two quantities is derived in an expression that is formally similar to the previous one, but with significantly different parameters. After having discussed the potential causes for such differences, it is suggested that the new relation should replace the old one for any future modeling of the numerous Lyα absorptions and emissions observed in the Solar System. 相似文献
17.
A quiescent prominence was observed in June 1997 by instruments onboard the SOHO spacecraft: the Solar Ultraviolet Measurements of Emitted Radiation (SUMER), Coronal Diagnostic Spectrometer (CDS) and Extreme-Ultraviolet Imaging Telescope (EIT), along with the coronagraph of the Wrocaw University Observatory at Bialków and the spectrograph of the Ondejov Observatory. We present prominence observations in higher lines of the hydrogen Lyman series (from L to L-9), together with some other UV lines obtained by SUMER. We extract the basic characteristics of the calibrated line profiles of these Lyman lines and compare them with the theoretical profiles computed from three kinds of NLTE models which also include prominence filamentation. Our principal result is that the current NLTE models are in principle capable of explaining the SUMER calibrated intensities in the observed Lyman lines. We also find that in order to fit all these lines, one has to consider a prominence-corona transition region (PCTR) with a temperature gradient. At low pressures, higher Lyman lines are still rather sensitive to the incident radiation which must be carefully taken into account in the modeling. From PCTR models, which also take into account the effect of ambipolar diffusion on the heating, we have derived the formation depths for the Lyman series lines. High Lyman lines seem to be formed just at the base of the PCTR. 相似文献
18.
Double pass photoelectric observations are presented of five Caii lines (H, K, 8498 Å, 8542 Å, and 8662 Å) in a number of solar plages of different degrees of activity, quiet regions, and a sunspot. The data are compared with previous work. All five lines show increasing emission together in plages and the least opaque of the infrared triplet lines appears to exhibit core emission prior to the more opaque members of the multiplet. The question of source function equality is considered and the differences and similarities among plage profiles and between plage and quiet profiles are shown qualitatively and quantitatively.Staff Member, Laboratory Astrophysics Division, National Bureau of Standards.Visiting Astronomer at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy. Inc., under contract with the National Science Foundation. 相似文献
19.
During several campaigns focused on prominences we have obtained coordinated spectral observations from the ground and from
space. The SOHO/SUMER spectrometer allows us to observe, among others, the whole Lyman series of hydrogen, while the Hα line was observed by the MSDP spectrograph at the VTT. For the Lyman lines, non-LTE radiative-transfer computations have
shown the importance of the optical thickness of the prominence – corona transition region (PCTR) and its relation to the
magnetic field orientation for the explanation of the observed line profiles. Moreover, Heinzel, Anzer, and Gunár (2005, Astron. Astrophys.
442, 331) developed a 2D magnetostatic model of prominence fine structures that demonstrates how the shapes of Lyman lines vary,
depending on the orientation of the magnetic field with respect to the line of sight. To support this result observationally,
we focus here on a round-shaped filament observed during three days as it was crossing the limb. The Lyman profiles observed
on the limb are different from day to day. We interpret these differences as being due to the change of orientation of the
prominence axis (and therefore the magnetic field direction) with respect to the line of sight. The Lyman lines are more reversed
if the line of sight is across the prominence axis as compared to the case when it is aligned along its axis. 相似文献
20.
Observations indicate that in plage areas (i.e. in active regions outside sunspots) acoustic waves travel faster than in the quiet Sun, leading to shortened travel times
and higher p-mode frequencies. Coupled with the 11-year variation of solar activity, this may also explain the solar cycle variation of
oscillation frequencies. While it is clear that the ultimate cause of any difference between the quiet Sun and plage is the
presence of magnetic fields of order 100 G in the latter, the mechanism by which the magnetic field exerts its influence has
not yet been conclusively identified. One possible such mechanism is suggested by the observation that granular motions in
plage areas tend to be slightly “abnormal”, dampened compared to the quiet Sun.
In this paper we consider the effect that abnormal granulation observed in active regions should have on the propagation of
acoustic waves. Any such effect is found to be limited to a shallow surface layer where sound waves propagate nearly vertically.
The magnetically suppressed turbulence implies higher sound speeds, leading to shorter travel times. This time shift Δ
τ is independent of the travel distance, while it shows a characteristic dependence on the assumed plage field strength. As
a consequence of the variation of the acoustic cutoff with height, Δ
τ is expected to be significantly higher for higher frequency waves within the observed regime of 3 – 5 mHz. The lower group
velocity near the upper reflection point further leads to an increased envelope time shift, as compared to the phase shift.
p-mode frequencies in plage areas are increased by a corresponding amount, Δ
ν/ν=ν
Δ
τ. These characteristics of the time and frequency shifts are in accordance with observations. The calculated overall amplitudes
of the time and frequency shifts are comparable to, but still significantly less than (by a factor of 2 to 5), those suggested
by measurements. 相似文献