利用辐射转移和流体动力学模拟程序RADYN研究了太阳大气对非热电子束加热的响应。描述非热电子能量分布的参数的时间演化来自硬X射线观测的一个特定的耀斑，我们比较了建模和观测参数。通过对RHESSI X射线能谱的分析，获得了2011年3月9日发生的X1. 5级太阳耀斑期间非热电子束参数的演化。RADYN耀斑模型允许演化110秒，之后电子束加热结束，然后允许继续演化300秒。模拟耀斑参数进行了比较，从极紫外光谱测定的观测参数。该模型产生了一个比观测到的更热、更密集的耀斑环，也更快地冷却，这表明在耀斑的衰变阶段需要额外的能量输入。在爆炸蒸发阶段，一个高密度的冷物质区域通过日冕向上传播。这种材料经历了温度的快速上升，因为它无法辐射掉所有通过非热电子束和热传导沉积在它上面的能量。耀斑过渡区底部的一个狭窄的高密度（$n_{e} \le 10^{15}$ cm $^{-3}$）区域是模式大气中的光学线发射源。在耀斑的整个演化过程中计算了电子的碰撞停止深度，发现低层大气的压缩可能允许电子更远地穿透到耀斑大气中，而不是安静的太阳大气。
英文摘要：
We investigated the response of the solar atmosphere to non-thermal electron beam heating using the radiative transfer and hydrodynamics modelling code RADYN. The temporal evolution of the parameters that describe the non-thermal electron energy distribution were derived from hard X-ray observations of a particular flare, and we compared the modelled and observed parameters. The evolution of the non-thermal electron beam parameters during the X1.5 solar flare on 2011 March 9 were obtained from analysis of RHESSI X-ray spectra. The RADYN flare model was allowed to evolve for 110 seconds, after which the electron beam heating was ended, and was then allowed to continue evolving for a further 300s. The modelled flare parameters were compared to the observed parameters determined from extreme-ultraviolet spectroscopy. The model produced a hotter and denser flare loop than that observed and also cooled more rapidly, suggesting that additional energy input in the decay phase of the flare is required. In the explosive evaporation phase a region of high-density cool material propagated upward through the corona. This material underwent a rapid increase in temperature as it was unable to radiate away all of the energy deposited across it by the non-thermal electron beam and via thermal conduction. A narrow and high-density ($n_{e} \le 10^{15}$ cm$^{-3}$) region at the base of the flare transition region was the source of optical line emission in the model atmosphere. The collision-stopping depth of electrons was calculated throughout the evolution of the flare, and it was found that the compression of the lower atmosphere may permit electrons to penetrate farther into a flaring atmosphere compared to a quiet Sun atmosphere.
The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares I: Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29
The X1 flare and associated filament eruption occurring in NOAA Active Region 12017 on SOL2014-03-29 has been the source of intense study. In this work, we analyse the results of a series of non linear force free field extrapolations of the pre and post flare period of the flare. In combination with observational data provided by the IRIS, Hinode and SDO missions, we have confirmed the existence of two flux ropes present within the active region prior to flaring. Of these two flux ropes, we find that intriguingly only one erupts during the X1 flare. We propose that the reason for this is due t…
This work is a continuation of Paper I [Sharykin et al., 2018] devoted to analysis of nonthermal electron dynamics and plasma heating in the confined M1.2 class solar flare SOL2015-03-15T22:43 revealing energy release in the highly sheared interacting magnetic loops in the low corona, above the polarity inversion line (PIL). The scope of the present work is to make the first extensive quantitative analysis of the photospheric magnetic field and photospheric vertical electric current (PVEC) dynamics in the confined flare region near the PIL using new vector magnetograms obtained with the Helios…
Spectroscopic observations made by the Extreme Ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) during the 2012 March 7 X5.4-class flare (SOL2012-03-07T00:07) are analyzed for signatures of the non-Maxwellian kappa-distributions. Observed spectra were averaged over 1 minute to increase photon statistics in weaker lines and the pre-flare spectrum was subtracted. Synthetic line intensities for the kappa-distributions are calculated using the KAPPA database. We find strong departures (kappa < 2) during the early and impulsive phases of the flare, with subsequ…
How important are electron beams in driving chromospheric evaporation in the 2014 March 29 flare?
我们提出了耀斑SOL 2014 -03- 29 T17：48色球蒸发的高空间分辨率观测。FeXXI 1354.1 A线的界面区域成像光谱仪（IRIS）观测表明，在耀斑峰值期间和进入衰变阶段的几分钟内，沿耀斑带在10 MK的温度下蒸发等离子体，上升流速度在30 km s $^{-1}$和200 km s $^{-1}$之间。在耀斑峰值期间，通过RHESSI观察硬X射线（HXR）足点两分钟。它们的位置与南部耀斑带部分上升气流的位置相吻合，但HXR足点源比FeXXI的上升气流早30-75秒。然而，在南部带状的其他部分和北部带状的观察到的上升流不符合HXR源的时间和空间，最突出的是在衰变阶段。在这种情况下，蒸发很可能是由能量输入引起的，通过在整个观测时间间隔内存在的热（25 MK）日冕源和色球层之间建立的传导通量。所提出的意见表明，传导可能会驱动蒸发不仅在衰变阶段，但也在耀斑峰值。电子束加热可能只在耀斑的初始阶段起驱动蒸发的作用。
The 2014 March 29 X-flare: sub-arcsecond resolution observations of Fe XXI 1354.1
界面区成像光谱仪（IRIS）是第一台通过Fe XXI $λ$ 1354.1禁线的成像光谱以亚角秒空间分辨率观测$\sim 10$ MK等离子体的太阳仪器。IRIS对2014年3月29日17：48 UT发生的X1级耀斑的观测显示，来自耀斑带和耀斑后环拱廊的Fe XXI发射。Fe XXI出现在所有的色球带位置，虽然通常有一个光栅（75秒）的延迟，有时偏移高达1 $^{\prime\prime}$。100- 200 km/s的$^{-1}$蓝移被发现在最明亮的丝带，表明热等离子体上升到日冕。Fe XXI的带状发射是紧凑的，空间范围为$< 2^{\prime\prime}$，并可以延伸到色球带的位置之外。发现在远离带状位置的方向上蓝移减少和增加的实例，并且在耀斑峰之后蓝移存在至少6分钟。在大气成像组件（AIA）131毫米滤光片图像中看到的耀斑后环拱廊主要由Fe XXI组成，表现出明亮的环顶，强度分布不对称。环顶的大小由$\ge 1^{\prime\prime}$的IRIS分辨，环顶的线宽并不比环腿宽，这表明环顶不是增强湍流的场所。环形拱廊中的视线速度通常为$<10$ km s $^{-1}$，平均非热运动从耀斑峰值时的43 km s $^{-1}$下降到6分钟后的26 km s $^{-1}$。如果假设环拱圈中的平均速度是静止的，那么它就意味着$1354.106\pm 0.023$的Fe …
The fast filament eruption leading to the X-flare on March 29, 2014
我们调查了导致太阳X1耀斑的事件序列SOL 2014 -03- 29 T17：48。由于与地面Dunn太阳望远镜和IRIS、Hinode、RHESSI、STEREO和SDO航天器对X耀斑进行了前所未有的联合观测，我们可以从光球层到日冕的许多太阳层进行采样。在先前磁通量出现的区域上方观察到暗条爆发，这可能导致磁场配置的变化，从而导致X耀斑。这是从硬X射线发射的时间和位置得出的结论，它在灯丝加速后不到一分钟就开始增加。在耀斑发生前的至少一个小时，暗条在色球温度下的多普勒速度为2-5 km s $\sim$，大部分是蓝移，但在其脚点附近也有红移。在耀斑爆发前15分钟，其色球多普勒频移增加到6-10 km/s $\sim$，可以观察到等离子体加热，然后以至少600 km/s $^{-1}$的速度升空，如IRIS数据所示。与以前的研究相比，这种加速度（$\sim$ 3-5 km s $^{-2}$）非常快，而速度在日冕物质抛射的常见范围内。一个有趣的特征是在喷发的丝状体附近有一个低洼的扭曲的第二丝状体，它似乎没有参与喷发。在耀斑带开始在第二个灯丝的每一个侧面，它似乎已经解开和消失在耀斑。这些观测结果是迄今为止X级耀斑的一些最高分辨率数据，并揭示了一些尚待解释的小尺度特征。
We present the study of SOL2015-03-15 M1.2 flare, revealing acceleration of electrons and plasma heating in the sheared twisted magnetic structure in the polarity inversion line (PIL). The scope is to make the analysis of nonthermal electrons dynamics and plasma heating in the highly stressed magnetic loops interacting in the PIL by using X-ray, microwave, ultraviolet, and optical observations. It is found that the most probable scenario for the energy release in the PIL is the tether-cutting magnetic reconnection between the low-lying (3 Mm above the photosphere) magnetic loops within a twist…
Quasi-periodic pulsations and three-dimensional magnetic reconnection during 2022 March 31 flare observed by IRIS & STIX
Bay Area Environmental Research Institute（湾区环境研究所）；Lockheed Martin Solar & Astrophysics Laboratory（洛马太阳能与天体物理实验室）；University of Applied Sciences and Arts Northwestern Switzerland (FHNW)（西北瑞士应用科学与艺术大学）；ETH Zürich（苏黎世联邦理工学院）；Oregon State University（俄勒冈州立大学）；Dublin Institute for Advanced Studies（都柏林高等研究院）；Southwest Research Institute（西南研究院）；SETI Institute（搜寻地外文明研究所）
Radiative losses in the chromosphere are very important in the energy balance. There have been efforts to make simple lookup tables for chromospheric radiative losses in the quiet Sun. During solar flares, the atmospheric conditions are quite different, and the currently available recipe of Gan & Fang (1990) is constructed from semi-empirical models. It remains to be evaluated how these recipes work in flare conditions. We aim to construct an approximate recipe of chromospheric radiative losses for solar flares. We follow the method of Carlsson & Leenaarts (2012) to tabulate the optically thin…
Context. Radiative losses are an indispensable part in the numerical simulation of flares. Detailed calculations could be computationally expensive, especially in the chromosphere. There have been some approximate recipes for chromospheric radiative losses in flares, yet their feasibility in flare simulations needs further evaluation. Aims. We aim to evaluate the performance of different recipes for chromospheric radiative losses in flare simulations. Methods. We compare the atmospheric structure and line profiles in beam-heated flares calculated with detailed radiative losses and the approxim…
Multi-point study of the energy release and transport in the 28 March 2022, M4-flare using STIX, EUI, and AIA during the first Solar Orbiter nominal mission perihelion
On 2014 March 29, an intense solar flare classified as X1.0 occurred in the active region 12017. Several associated phenomena accompanied this event, among them a fast-filament eruption, large-scale propagating disturbances in the corona and the chromosphere including a Moreton wave, and a coronal mass ejection. This flare was successfully detected in multiwavelength imaging in H-alpha line by the Flare Monitoring Telescope (FMT) at Ica University, Peru. We present a detailed study of the Moreton wave associated with the flare in question. Special attention is paid to the Doppler characteristi…
Solar flares release an enormous amount of energy into the corona. A substantial fraction of this energy is transported to the lower atmosphere, which results in chromospheric heating. The mechanisms that transport energy to the lower solar atmosphere during a flare are still not fully understood. We aim to estimate the temporal evolution of the radiative losses in the chromosphere at the footpoints of a C-class flare, in order to set observational constraints on the electron beam parameters of a RADYN flare simulation. We estimated the radiative losses from hydrogen, and singly ionized Ca and…
In this study, we investigated the energy partition of four confined circular-ribbon flares (CRFs) near the solar disk center, which are observed simultaneously by SDO, GOES, and RHESSI. We calculated different energy components, including the radiative outputs in 1$-$8, 1$-$70, and 70$-$370 Å, total radiative loss, peak thermal energy derived from GOES and RHESSI, nonthermal energy in flare-accelerated electrons, and magnetic free energy before flares. It is found that the energy components increase systematically with the flare class, indicating that more energies are involved in larger flar…
Gyrosynchrotron radiation is produced by solar flares, and can be used to infer properties of the accelerated electrons and magnetic field of the flaring region. This microwave emission is highly dependent on many local plasma parameters, and the viewing angle. To correctly interpret observations, detailed simulations of the emission are required. Additionally, gyrosynchrotron emission from the chromosphere has been largely ignored in modelling efforts, and recent studies have shown the importance of thermal emission at millimetric wavelengths. Thyr is a new tool for modelling microwave emissi…
Numerical models of solar flares typically focus on the behaviour of directly-heated flare models, adopting magnetic field- aligned, plane-parallel methodologies. With high spatial- and spectral-resolution ground-based optical observations of flares, it is essential also to understand the response of the plasma surrounding these strongly heated volumes. We investigate the effects of the extreme radiation field produced by a heated column of flare plasma on an adjacent slab of chromospheric plasma, using a two-dimensional radiative transfer model and considering the time-dependent solution to t…
In this paper, we investigate the energy partition of two homologous M1.1 circular-ribbon flares (CRFs) in active region (AR) 12434. They were observed by \textit{SDO}, \textit{GOES}, and \textit{RHESSI} on 2015 October 15 and 16, respectively. The peak thermal energy, nonthermal energy of flare-accelerated electrons, total radiative loss of hot plasma, and radiant energies in 1$-$8 Å and 1$-$70 Å of the flares are calculated. The two flares have similar energetics. The peak thermal energies are (1.94$\pm$0.13)$\times$10$^{30}$ erg. The nonthermal energies in flare-accelerated electrons are (3…
Data-driven Radiative Magnetohydrodynamics Simulations with the MURaM Code: the Emergence of Active Region 11158 and the X2.2 Flare
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（现代天文学和天体物理学教育部重点实验室（南京大学））
Influence of Cross-sectional Expansion on Coronal Emissions from a Radiatively Cooling Solar Flare Loop
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（教育部现代天文学和天体物理学重点实验室（南京大学））
Context. On the sun, the magnetic field vector is measured routinely only in the photosphere. By using these photospheric measurements as boundary condition, we developed the magnetohydrostatic (MHS) extrapolation to model the solar atmosphere. The model makes assumption about the relative importance of magnetic and non-magnetic forces. While the solar corona is force-free, this is not the case in photosphere and chromosphere. Aim. The model has been tested with an exact equilibria in \cite{zw18}. Here we present a more challenging and realistic test of our model with radiative MHD simulation …
Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Solar Flare Loops
INAF Osservatorio Astronomico di Roma（罗马天文台）；NASA Goddard Space Flight Center（NASA戈达德太空飞行中心）；Universities Space Research Association（大学空间研究协会）；Mullard Space Science Laboratory, University College London（伦敦大学学院穆拉德空间科学实验室）；Northumbria University（诺森比亚大学）；Computational Physics Inc.（计算物理公司）；Dublin City University（都柏林城市大学）；Dublin Institute for Advanced Studies（都柏林高等研究院）；Konkoly Observatory（孔科利天文台）
It is widely believed that magnetic flux ropes are the key structure of solar eruptions; however, their observable counterparts are not clear yet. We study a flare associated with flux rope eruption in a comprehensive radiative magnetohydrodynamic simulation of flare-productive active regions, especially focusing on the thermodynamic properties of the plasma involved in the eruption and their relation to the magnetic flux rope. The pre-existing flux rope, which carries cold and dense plasma, rises quasi-statically before the eruption onsets. During this stage, the flux rope does not show obvio…
Solar Flare Chromospheric Line Emission: Comparison Between IBIS High-resolution Observations and Radiative Hydrodynamic Simulations
太阳耀斑涉及脉冲能量释放，这导致在宽光谱范围和宽高度范围内的辐射增强。特别是，从色球层的线发射可以提供等离子体加热过程的关键诊断。因此，高分辨率光谱观测和先进的数值模拟结果之间的直接比较可能是非常有价值的，但尚未尝试。在本文中，我们提出了在本文中这样一个自洽调查的M3.0耀斑观测的邓恩太阳望远镜的干涉二维光谱仪（IBIS）在2011年9月24日，我们与辐射流体动力学代码RADYN建模。我们用IBIS在H $α$ 6563和Ca II 8542中获得了耀斑区的图像和光谱，并用X射线的Ramaty高能太阳光谱成像仪（RHESSI）获得了耀斑区的图像和光谱。后者的观测被用来推断非热电子的人口，这是通过RADYN模拟大气响应电子碰撞加热。然后，我们合成了谱线，并将它们的形状和强度与IBIS观察到的进行了比较，发现两者基本一致。特别是，合成的Ca II 8542钙离子谱与观察到的谱拟合良好，而合成的H $α$谱在岩心中比观察到的更暗。这表明H $α$发射比Ca II 8542发射对非热电子通量更敏感。我们认为，有必要改进能量输入和其他过程是必要的，以解决这种差异。
White-light flares are the flares with emissions visible in the optical continuum. They are thought to be rare and pose the most stringent requirements in energy transport and heating in the lower atmosphere. Here we present a nearly circular white-light flare on 2015 March 10 that was well observed by the Optical and Near-infrared Solar Eruption Tracer and Solar Dynamics Observatory. In this flare, there appear simultaneously both impulsive and gradual white-light kernels. The generally accepted thick-target model would be responsible for the impulsive kernels but not sufficient to interpret …
Type II WLFs have weak Balmer line emission and no Balmer jump. We carried out a set of radiative hydrodynamic simulations to understand how the hydrogen radiative losses vary with the electron beam parameters and more specifically with the low energy cutoff. Our results have revealed that for low energy beams, the excess flare Lyman emission diminishes with increasing low energy cutoff as the energy deposited into the top chromosphere is low compared to the energy deposited into the deeper layers. Some Balmer excess emission is always present and is driven primarily by direct heating from the…
As one of the most violent activities in the solar atmosphere, white-light flares (WLFs) are generally known for their enhanced white-light (or continuum) emission, which primarily originates in the solar lower atmosphere. However, we know little about how white-light emission is produced. In this study, we aim to investigate the response of the continua at 3600Å and 4250Å and also the H$α$ and Ly$α$ lines during WLFs modeled with radiative hydrodynamics simulations. We take non-thermal electron beams as the energy source for the WLFs in two different initial atmospheres and vary their paramet…
Using the observations from the Optical and Near-infrared Solar Eruption Tracer and the Solar Dynamics Observatory, we study an M5.7 flare in AR 11476 on 2012 May 10 and a micro-flare in the quiet Sun on 2017 March 23. Before the onset of each flare, there is a reverse S-shaped filament above the polarity inversion line. Then the filaments become unstable and begin to rise. The rising filaments gain the upper hand over the tension force of the dome-like overlying loops and thus successfully erupt outward. The footpoints of the reconnecting overlying loops successively brighten and are observed…
