The only prominent line of singly ionized helium in the visible spectral range, helium-II 4686 A, is observed together with the helium-I 5015 A singlet and the helium-I 4471 A triplet line in solar prominences. The sodium emission, NaD2, is used as a tracer for helium-II emissions which are sufficiently bright to exceed the noise level near 10^-6 of the disk-center intensity. The so selected prominences are characterized by small non-thermal line broadening and almost absent velocity shifts, yielding narrow line profiles without wiggles. The reduced widths [Delta(lambda_D) / lambda] of helium-II 4686 A are 1.5 times broader than those of helium-I 4471 A triplet and 1.65 times broader than those of helium-I 5015 A singlet. This indicates that the helium lines originate in a prominence--corona transition region with outwards increasing temperature.
Solar prominences are formed by partially ionized plasma with inter-particle collision frequencies generally warranting magnetohydrodynamic treatment. In this work, we explore the dynamical impacts and observable signatures of two-fluid effects in the parameter regimes when ion-neutral collisions do not fully couple the neutral and charged fluids. We perform 2.5D two-fluid (charges - neutrals) simulations of the Rayleigh-Taylor instability (RTI) at a smoothly changing interface between a solar prominence thread and the corona. The purpose of this study is to deepen our understanding of the RTI…
Solar prominences are magnetic structures incarcerating cool and dense gas in an otherwise hot solar corona. Prominences can be categorized as quiescent and active. Their origin and the presence of cool gas (~$10^4$K) within the hot (~$10^6$K) solar corona remains poorly understood. The structure and dynamics of solar prominences was investigated in a large number of observational and theoretical (both analytical and numerical) studies. In this paper, an analytic model of quiescent solar prominence is developed and used to demonstrate that the prominence velocity increases exponentially, which…
The Spontaneous Genesis of Solar Prominence Structures Driven by Supergranulation in Three-Dimensional Simulations
School of Physics and Astronomy, Yunnan University（云南大学物理与天文学院）；Yunnan Key Laboratory of Solar Physics and Space Science（云南太阳能物理与空间科学重点实验室）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
Prominences are incredibly dynamic across the whole range of their observable spatial scales, with observations revealing gravity-driven fluid instabilities, waves, and turbulence. With all these complex motions, it would be expected that instabilities driven by shear in the internal fluid motions would develop. However, evidence of these have been lacking. Here we present the discovery in a prominence, using observations from the Interface Region Imaging Spectrograph (IRIS), of a shear flow instability, the Kelvin-Helmholtz sinusoidal-mode of a fluid channel, driven by flows in the prominence…
Although the real shapes and trajectories of erupting solar prominences in three dimensions have been intensively studied, the three-dimensional (3D) shapes of stable prominences before eruptions have not been measured accurately so far. We intend to make such a measurement to constrain 3D prominence models and to extend our knowledge of prominences. Using multiperspective observations from the Atmospheric Imaging Assembly on board SDO and the Extreme Ultraviolet Imager on board STEREO, we reconstructed 3D coordinates of three stable prominences: a quiescent, an intermediate, and a mixed type.…
Solar filaments are dark structures on the solar disk, with an elongated spine and several barbs extending out from the spine. When appearing above the solar limb, a filament is called a prominence, with several feet extending down to the solar surface. It was generally thought that filament barbs are simply the prominence feet veering away from the spine and down to the solar surface. However, it was recently noticed that there might be another dynamic type of barbs, which were proposed to be due to filament thread longitudinal oscillation. If this is the case, the dynamic barbs would not ext…
A solar filament is a dense cool condensation that is supported and thermally insulated by magnetic fields in the rarefied hot corona. Its evolution and stability, leading to either an eruption or disappearance, depend on its coupling with the surrounding hot corona through a thin transition region, where the temperature steeply rises. However, the heating and dynamics of this transition region remain elusive. We report extreme-ultraviolet observations of quiescent filaments from the Solar Dynamics Observatory that reveal prominence spicules propagating through the transition region of the fil…
Although the present-day Sun rotates too slowly to exhibit centrifugally-supported 'slingshot prominences', at some time during its past it may have formed these clouds of cool gas and ejected them into the interplanetary medium. We determine the time period for this behaviour by using a rotation evolution code to derive the properties of the formation and ejection of slingshot prominences during the lifetime of a star similar to our Sun. The mass, mass loss rate and rate of ejection of these prominences are calculated using the analytical expression derived in our previous work. We find that …
Quiescent prominence dynamics observed with the Hinode Solar Optical Telescope . II. Prominence Bubble Boundary Layer Characteristics and the Onset of a Coupled Kelvin-Helmholtz Rayleigh-Taylor Instability
Aims : We present 24 synoptic maps of solar filaments, in which the average unambiguous magnetic field vectors of 296 prominences were determined with Pic-du-Midi observations between 1974 and 1982. This was the ascending phase of cycle 21. Methods : The magnetic field was determined by interpreting the Hanle effect, which is observed in the \ion{He}{i} D$_3$ line. Previous results for the prominence field polarity and prominence chirality were applied to solve the fundamental ambiguity. The measurements were averaged in each prominence for accuracy reasons. Results : The result is twofold. Fi…
On the Branching in the Emission Relations of Ca II lines in Solar Prominences
我们同时观察到的Ca II K，Ca II 8542和H-β的排放在太阳能电池在高空间和光谱分辨率。我们确认分支的钙II和H-β的发射关系。这与非热谱线展宽有关，其对Ca II谱线的影响远大于H-β。经典的非热（麦克斯韦）线加宽，确定由氢线的宽度与钙线的宽度比较，是不足以解释钙II宽度。这表明了未解决的日珥精细结构的大尺度运动的额外增宽。
We report observations of a unique, large prominence eruption that was observed in the He II 304 Å passband of the the Extreme Ultraviolet Imager/Full Sun Imager telescope aboard Solar Orbiter on 15-16 February 2022. Observations from several vantage points (Solar Orbiter, the Solar-Terrestrial Relations Observatory, the Solar and Heliospheric Observatory, and Earth-orbiting satellites) were used to measure the kinematics of the erupting prominence and the associated coronal mass ejection. Three-dimensional reconstruction was used to calculate the deprojected positions and speeds of different …
The first ionization potential (FIP) bias is currently used to trace the propagation of solar features ejected by the wind and solar eruptions (coronal mass ejections). The FIP bias also helps us to understand the formation of prominences, as it is a tracer for the solar origin of prominence plasma. This work aims to provide elemental composition and FIP bias in quiescent solar prominences. This is key information to link these features to remnants of solar eruptions measured in-situ within the heliosphere and to constrain the coronal or photospheric origin of prominence plasma. We used the di…
We present a new methodology -- the Keplerian Optical Dynamics Analysis (KODA) -- for analyzing the dynamics of dense, cool material in the solar corona. The technique involves adaptive spatiotemporal tracking of propagating intensity gradients and their characterization in terms of time-evolving Keplerian areas swept out by the position vectors of moving plasma blobs. Whereas gravity induces purely ballistic motions consistent with Kepler's second law, non-central forces such as the Lorentz force introduce non-zero torques resulting in more complex motions. KODA algorithms enable direct evalu…
We present the first observation of a solar prominence at $84-116$ GHz using the high resolution interferometric imaging of ALMA. Simultaneous observations in H$α$ from Białkaw Observatory and with SDO/AIA reveal similar prominence morphology to the ALMA observation. The contribution functions of 3 mm and H$α$ emission are shown to have significant overlap across a range of gas pressures. We estimate the maximum millimetre-continuum optical thickness to be $τ_\mathrm{3mm}\approx 2$, and the brightness temperature from the observed H$α$ intensity. The brightness temperature measured by ALMA is …
Solar prominences are structures of importance because of their role in polar field reversal. We study the long-term variation of the time latitude distribution of solar prominences in this article. To accomplish this, we primarily used the digitised disc-blocked Ca II K spectroheliograms as recorded from Kodaikanal Solar Observatory for the period of 1906 -- 2002. For improving the data statistics we included full disc H_alpha images from Meudon and Kanzelhohe Observatory which are available after 1980. We developed an automated technique to identify the latitudinal locations of prominences i…
The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He I 10830 A triplet
内容：通过解释谱线中的汉勒效应和塞曼效应，可以确定静止太阳黑子中的磁场矢量。然而，观测测量是稀缺的，缺乏高空间分辨率。目的：通过解释安装在泰德天文台的德国真空塔望远镜上的特内里费红外偏振计获得的He I 1083.0 nm三重态的分光偏振测量，确定沿静止日珥的磁场矢量配置。方法. He I 1083.0 nm三重态Stokes分布进行了分析，考虑到在这三重态的偏振信号的物理负责的反演代码。借助太阳动态观测台和日地关系观测台卫星进行的极紫外线观测，将结果纳入太阳背景。结果：对于最可能的磁场矢量配置，分析描绘了7高斯的平均场强。我们没有发现磁场强度的局部变化，只是平均而言，日珥体中的磁场强度低于日珥脚中的磁场强度，日珥脚中的磁场强度达到25高斯。相对于局部垂直线的平均磁场倾斜度为77度。磁场矢量与日珥主轴的锐角在左旋手征情况下为24度，在右旋手征情况下为58度。这些推论是在粗略的协议与以前的结果从较低的空间分辨率获得的数据分析。
The triggering process for coronal mass ejections (CME) in the solar atmosphere is not fully understood. We use observations from different spacecraft at several wavelengths to detect an instability process for a prominence/filament with a subsequent eruption of CME. Time series of spectral lines at 304, 171, 193, and 211 Å have been obtained with the SDO spacecraft, and at 304, 171, 195, and 284 Å with the STEREO spacecraft. A prominence/filament system was observed during November 8-23, 2011, at different angles by SDO, STEREO_A, and STEREO_B. The observations show that a giant tornado began…
Prominence plumes are evacuated upflows that emerge from bubbles below prominences, whose formation mechanism is still unclear. Here we present a detailed study of plumes in a quiescent prominence using the high-resolution H-alpha filtergrams at the line center as well as line wing at +/-0.4 angstrom from the New Vacuum Solar Telescope. Enhancements of brightening, blue shifts, and turbulence at the fronts of plumes are found during their formation. Some large plumes split at their heads and finger-shaped structures are formed between them. Blue-shifted flows along the bubble-prominence interf…
Analyses on Wassenius' Report for Total Solar Eclipse in 1733: Quantifications of the Solar Radius and the Earliest Reported Prominences
Nagoya University（名古屋大学）；RAL Space, Rutherford Appleton Laboratory, Science and Technology Facilities Council（卢瑟福·阿普尔顿实验室空间物理与操作部门，科学与技术设施委员会）；Riken（理化学研究所）；National Astronomical Observatory of Japan（日本国立天文台）；University of Amsterdam（阿姆斯特丹大学）；Université de la Côte d'Azur（蔚蓝海岸大学）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；National Solar Observatory（美国国家太阳天文台）
SDO/AIA Detection of Solar Prominence Formation within a Coronal Cavity
我们报告的第一个分析SDO/AIA观测的形成一个静止的极冠突出的冕腔。He II 304 He（log T_{max} ~ 4.8 K）数据显示，由于等离子体的垂直引流和横向输送，日珥逐渐消失，约12小时后形成新的日珥。在日珥形成之前，在冕腔的中心区域会出现明亮的发射“云”。云的峰值亮度在时间上从Fe XIV 211通道，通过Fe XII 193通道，到Fe IX 171通道逐渐移动（log T_{max}分别为6.2，6.1，5.8 K），同时高度降低。过滤器比分析估计的云在腔中的初始温度约为log T \sim 6.25 K的冷却随着时间的推移的证据。随后日珥的增长伴随着211通道中空洞的变暗。这些观测结果暗示了通过冕腔中热等离子体的原位冷凝形成日珥的可能性，支持了日冕磁通量绳中磁热对流的拟议过程。
Measuring vector magnetic fields in solar prominences
我们目前的分光偏振观测在他我1083.0 nm多重的一个静止的，树篱日珥。这些数据是用特内里费岛红外线偏振计拍摄的，该偏振计安装在位于西班牙加那利群岛特内里费岛天文台（Observatorio del Teide）的德国真空塔望远镜上。所观察到的He I圆偏振和线偏振信号分别由塞曼效应和原子级偏振和汉勒效应主导。这些可观测量对视场的每个空间点处的磁场矢量的强度和方向敏感。我们确定的磁场矢量的日珥应用HAZEL反演代码所观察到的斯托克斯轮廓。我们简要讨论了检索的磁场矢量配置。
In this work, we explore the dynamical impacts and observable signatures of two-fluid effects in the parameter regimes when ion-neutral collisions do not fully couple the neutral and charged fluids. The purpose of this study is to deepen our understanding of the RTI and the effects of the partial ionization on the development of RTI using non-linear two-fluid numerical simulations. Our two-fluid model takes into account neutral viscosity, thermal conductivity, and collisional interaction between neutrals and charges: ionization/recombination, energy and momentum transfer, and frictional heatin…
The knots in solar prominences are often observed to fall with nearly constant velocity, but the associated physical mechanism is currently not well understood. In this letter, we presented a prominence observed by New Vacuum Solar Telescope (NVST) in H-alpha wavelength. Knots that rose within the prominence appear to have been preferentially located at higher altitude, whereas those that fell were found throughout the entire prominence structure. The descending speed of the knots near the solar surface was higher than that far away from the solar surface. We noted that the knots near the sola…
