We analyse the temporal evolution of the Differential Emission Measure (DEM) of solar active regions and explore its usage in solar flare prediction. The DEM maps are provided by the Gaussian Atmospheric Imaging Assembly (GAIA-DEM) archive, calculated assuming a Gaussian dependence of the DEM on the logarithmic temperature. We analyse time-series of sixteen solar active regions and a statistically significant sample of 9454 point-in-time observations corresponding to hundreds of regions observed during solar cycle 24. The time-series analysis shows that the temporal derivatives of the Emission Measure dEM/dt and the maximum DEM temperature dTmax/dt frequently exhibit high positive values a few hours before M- and X-class flares, indicating that flaring regions become brighter and hotter as the flare onset approaches. From the point-in-time observations we compute the conditional probabilities of flare occurrences using the distributions of positive values of the dEM/dt, and dTmax/dt and compare them with corresponding flaring probabilities of the total unsigned magnetic flux, a conventionally used, standard flare predictor. For C-class flares, conditional probabilities have lower or similar values with the ones derived for the unsigned magnetic flux, for 24 and 12 hours forecast windows. For M- and X-class flares, these probabilities are higher than those of the unsigned flux for higher parameter values. Shorter forecast windows improve the conditional probabilities of dEM/dt, and dTmax/dt in comparison to those of the unsigned magnetic flux. We conclude that flare forerunner events such as preflare heating or small flare activity prior to major flares reflect on the temporal evolution of EM and Tmax. Of these two, the temporal derivative of the EM could conceivably be used as a credible precursor, or short-term predictor, of an imminent flare.
Slipping Magnetic Reconnection of Flux Rope Structures as a Precursor to an Eruptive X-class Solar Flare
我们介绍了在2015年3月11日爆发的X级耀斑爆发之前磁绳结构的准周期滑动运动，由\emph{Interface Region Imaging Spectrograph}（\emph{IRIS}）和\emph{Solar Dynamics Observatory}（\emph{SDO}）获得。滑动运动发生在磁绳的北部，似乎是连续剥离磁绳。滑动速度为30 $-$ 40 km s $^{-1}$，平均周期为130 $\pm$ 30 s。Si { \sc iv} 1402.77 X线在滑动构造的西端表现出10 $-$ 30 km s $^{-1}$的红移和50 $-$ 120 km s $^{-1}$的线宽，表明了向下的重联流。滑动运动持续约40 min，在滑动后期，磁绳开始缓慢上升。然后，一个X2.1耀斑被启动，通量绳被脉冲加速。其中一个耀斑带扫过一个负极性的太阳黑子，在耀斑之后，太阳黑子的半影部分迅速衰减。我们研究了耀斑区的磁拓扑结构，结果表明存在扭曲的磁通绳，以及约束磁通绳的准分界线层（QSL）结构。我们的观测结果表明，在耀斑爆发前，准周期滑动磁重联发生在与磁通绳相关的QSL上，它驱动了后来的磁通绳爆发和耀斑爆发。
Multiwavelength Observations of the Precursors Before the Eruptive X4.9 Limb Solar Flare on 25 February, 2014: Current Sheet, Eruptive Filament, Flare and Eruption Onset in the Frame of the Tether-Cutting Magnetic Reconnection Scenario
Plasma Heating and Energization in Hot-Onset Flare Precursor Events
IREAP, University of Maryland（马里兰大学 IREAP）；Dept. of Physics, Institute for Physical Science and Technology, and the Joint Space Science Institute, University of Maryland（马里兰大学物理系、物理科学与技术研究所和联合空间科学研究所）
Identification of Pre-flare Processes and Their Possible Role in Driving a Large-scale Flux Rope Eruption with Complex M-class Flare in the Active Region NOAA 12371
A Data-constrained Magnetohydrodynamic Simulation of Successive X-class Flares in Solar Active Region 13842. II. Dynamics of the Solar Eruption Associated with the X9.0 Solar Flare
The Influence of Solar Flares on the Lower Solar Atmosphere: Evidence from the Na D Absorption Line Measured by GOLF/SOHO
据推测，太阳耀斑对太阳大气层的最深层有影响，但这种影响的观测证据很少。使用十年的测量Na D $_{1}$和Na D $_2$夫琅和费线，测量的GOLF船上SOHO，我们表明，这光球线确实是受耀斑。个别耀斑的影响被太阳振荡所掩盖，但基于条件平均的统计分析揭示了一个清晰的信号。虽然GOLF只能探测一个单一的波长在同一时间，我们表明，两翼的钠线仍然可以比较。变化的线不对称性可以被解释为在耀斑的峰值期间来自低层太阳大气的向上的等离子体运动，随后是向下的运动。
The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope
利用IRIS高分辨率成像系统研究了太阳耀斑硬X射线脉冲相色球发射谱线的30 s演化。辐射流体动力学耀斑模型表明，这些红移一般是由电子束产生的色球凝聚再现。该模型产生大的环境电子密度，和氢巴耳末系列的压力加宽应很容易检测到的观测。为了准确地解释即将到来的光谱数据的耀斑与DKIST，我们将非理想的，非绝热线展宽的氢到RADYN代码。这些改进允许在太阳耀斑的极端巴耳末线翼增强时间依赖的预测。我们研究了两个色球凝聚模型，它涵盖了耀斑色球中电子束流（$1-5 \times 10^{11}$ erg s $^{-1}$ cm $^{-2}$）和环境电子密度（$1 - 60 \times 10^{13}$ cm $^{-3}$）的范围。这两种模型产生的光束加热的发病10秒内的加宽和红移的变化。在色球凝聚中，由于H $α$、H $β$和H $γ$处的光学深度较大，光谱展宽增强，而巴尔末系列H12 $-$ H16的光学深度较低，为凝聚下方的束加热层中较小的电子密度提供了一个半透明窗口。太阳耀斑的典型DKIST/ViSP光谱的波长范围将足以检验极端氢翼加宽的预测，并精确地限制色球凝聚中的大密度。
A Data-constrained Magnetohydrodynamic Simulation of Successive X-class Flares in Solar Active Region 13842 I. Dynamics of the Solar Eruption Associated with the X7.1 Solar Flare
Optical Continuum Light Curves and Bolometric Energy Estimates of Solar White-light Flares
State Key Laboratory of Solar Activity and Space Weather, National Astronomical Observatories, Chinese Academy of Science（中国科学院国家天文台太阳活动与空间天气国家重点实验室）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台光学天文重点实验室）；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；School of Astronomy and Space Sciences, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与天体物理前沿研究院）；New Cornerstone Science Laboratory, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台新基石科学实验室）
Multi-wavelength view of an M2.2 Solar Flare on 26 November 2000
在本文中，我们提出了一个M2.2级太阳耀斑的2000年11月26日从NOAA AR 9236的研究。各种地面观测站（ARIES，Learmonths Solar Observatory）和空间仪器（SOHO，HXRS，GOES）在02：30 UT至04：00 UT的时间间隔内都很好地观测到了耀斑。耀斑起始于长弧形外耀斑带。之后，主耀斑开始与两个主要带。最初，外带开始以平均速率（$\sim$ 20 km s $^{-1}$）膨胀，随后显示收缩。耀斑与部分晕日冕物质抛射（CME），其平均速率为495公里/秒$^{-1}$。SOHO/MDI观测表明，活动区为四极磁位形。在耀斑爆发前，观测到耀斑附近的通量抵消现象。我们的分析表明耀斑是由磁爆发机制引发的。
