FERMI-LAT is performing an all-sky gamma-ray survey from 20 MeV to >300 GeV with unprecedented sensitivity and angular resolution. FERMI is the only mission able to detect high energy (>20 MeV) emission from the Sun during the new solar cycle 24. FERMI was launched on June 2008, since then high energy emission from the Sun was continuously monitored searching for flare events. Upper limits were derived for all the solar flares detected by other missions and experiments (RHESSI, FERMI-GBM, GOES). We present the analysis techniques used for this study and the preliminary results obtained so far.
Context: Active M dwarfs frequently exhibit large flares, which can pose an existential threat to the habitability of any planet in orbit in addition to making said planets more difficult to detect. M dwarfs do not lose angular momentum as easily as earlier-type stars, which maintain the high levels of stellar activity for far longer. Studying young, fast-rotating M dwarfs is key to understanding their near stellar environment and the evolution of activity Aims: We study stellar activity on the fast-rotating M dwarf GJ 3270. Methods: We analyzed dedicated high cadence, simultaneous, photometri…
The solar group at the National Astronomical Observatory of Japan is conducting synoptic solar observations with the Solar Flare Telescope. While it is a part of a long-term solar monitoring, contributing to the study of solar dynamo governing solar activity cycles, it is also an attempt at contributing to space weather research. The observations include imaging with filters for H$α$, Ca K, G-band, and continuum, and spectropolarimetry at the wavelength bands including the He I 1083.0 nm / Si I 1082.7 nm and the Fe I 1564.8 nm lines. Data for the brightness, Doppler signal, and magnetic field …
We present the Fermi-LAT observations of the behind-the-limb (BTL) flare of July 17, 2021 and the joint detection of this flare by STIX onboard Solar Orbiter. The separation between Earth and the Solar Orbiter was 99.2$^{\circ}$ at 05:00 UT, allowing STIX to have a front view of the flare. The location of the flare was ~S20E140 in Stonyhurst heliographic coordinates making this the most distant behind-the-limb flare ever detected in $>$100 MeV gamma-rays. The LAT detection lasted for $\sim$16 minutes, the peak flux was $ 3.6 \pm 0.8 $ (10$^{-5}$) ph cm$^{-2}$ s$^{-1}$ with a significance $>$15…
In this paper, we reanalyze the M1.2 confined flare with a large extreme-ultraviolet (EUV) late phase on 2011 September 9, focusing on its energy partition. The radiation ($\sim$5.4$\times$10$^{30}$ erg) in 1$-$70 Å is nearly eleven times larger than the radiation in 70$-$370 Å, and is nearly 180 times larger than the radiation in 1$-$8 Å. The peak thermal energy of the post-flare loops is estimated to be (1.7$-$1.8)$\times$10$^{30}$ erg based on a simplified schematic cartoon. Based on previous results of Enthalpy-Based Thermal Evolution of Loops (EBTEL) simulation, the energy inputs in the m…
We present in this reference paper an instrumental project dedicated to the monitoring of solar activity during solar cycle 25. It concerns the survey of fast evolving chromospheric events implied in Space Weather, such as flares, coronal mass ejections, filament instabilities and Moreton waves. Coronal waves are produced by large flares around the solar maximum and propagate with chromospheric counterparts; they are rare, faint, difficult to observe, and for that reason, challenging. They require systematic observations with automatic, fast and multi-channel optical instruments. MeteoSpace is…
Intermittent maser flare around the high mass young stellar object G353.273+0.641 I: data & overview
我们用VERA（VLBI射电天体测量探测）和Tomakamai 11米射电望远镜对高质量年轻天体G353.273+0.641的22 GHz H $_{2}$ O脉泽辐射进行了VLBI和单碟观测。两次脉泽耀斑被探测到，相隔近两年。频繁的VLBI监测显示，这些耀斑活动一直伴随着结构的变化，突出的冲击波阵面跟踪H2O脉泽的路线。我们只探测到了蓝移辐射，尽管速度范围很宽（> 100 km/s $^{-1}$），但所有脉泽特征都分布在200 $\times$ 200 au $^{2}$的很小区域内。光变曲线显示出明显的间歇性变化，表明G353.273+0.641的H $_{2}$ O脉泽是由幕式射电喷流激发的。\sim 2年的时间尺度和\sim 500 km s $^{-1}$的特征速度也支持这一解释。C50（-53 \pm 7 km s $^{-1}$）和C70（-73 \pm 7 km s $^{-1}$）的两个孤立速度分量显示了在耀斑阶段通量加权$V_{\rmn{LSR}}$值（\sim-5 km s $^{-1}$ yr $^{-1}$）的同步线性加速。这可以转换为1.1 \times 10 $^{-3}$ M $_{\sun}$ km s $^{-1}$ yr $^{-1}$的下限动量率。特别是与IRAS 20126+4104的脉泽性质非常相似。这证实了先前的建议，即G353.27…
Long-Baseline VLF Observations of Solar Flares from Antarctica
Institute of Astronomy and NAO, Bulgarian Academy of Sciences（保加利亚科学院天体物理与国家天文台研究所）；Technical University of Sofia（索菲亚理工大学）；Nikola Vaptsarov Naval Academy（尼古拉·瓦普察罗夫海军学院）
Recently detected coherent low-frequency radio emission from M dwarf systems shares phenomenological similarities with emission produced by magnetospheric processes from the gas giant planets of our Solar System. Such beamed electron-cyclotron maser emission can be driven by a star-planet interaction or a breakdown in co-rotation between a rotating plasma disk and a stellar magnetosphere. Both models suggest that the radio emission could be periodic. Here we present the longest low-frequency interferometric monitoring campaign of an M dwarf system, composed of twenty-one $\approx$8 hour epochs…
Recent observations in extreme-ultraviolet (EUV) wavelengths reveal a new late phase in some solar flares, which is seen as a second peak in warm coronal emissions ($\sim3$ MK) several tens of minutes to a few hours after the soft X-ray (SXR) peak. The origin of the EUV late phase (ELP) is explained by either a long-lasting cooling process in the long ELP loops, or a delayed energy ejection into the ELP loops well after the main flare heating. Using the observations with the \emph{Solar Dynamics Observatory} (\emph{SDO}), we investigate the production of the ELP in six homologous flares (F1--F…
Coherent Lateral Motion of Penumbral Filaments during X-class Flare
现在，对Hinode航天器搭载的天基50厘米太阳光学望远镜拍摄的太阳光球层高分辨率照片进行了例行观测。2006年12月13日，日野号拍摄了NOAA 10930中的三角洲黑子，当时该活动区发生了X级耀斑。两个明亮的丝带可见，即使在白光和G-波段的图像除了色球Ca II H图像。我们使用互相关技术对太阳黑子进行了全球登记，并分析了耀斑间隔期间的局部效应。我们发现在耀斑期间，半影暗条有横向运动。此外，我们定位两个补丁，一个在任何极性，这表明收敛运动的极性反转线（PIL）。在钙II H图像中，我们发现内核与耀斑前的增亮，位于沿PIL。
We developed an operational solar flare prediction model using deep neural networks, named Deep Flare Net (DeFN). DeFN can issue probabilistic forecasts of solar flares in two categories, such as >=M-class and <M-class events or >=C-class and <C-class events, occurring in the next 24 h after observations and the maximum class of flares occurring in the next 24 h. DeFN is set to run every 6 h and has been operated since January 2019. The input database of solar observation images taken by the Solar Dynamic Observatory (SDO) is downloaded from the data archive operated by the Joint Science Opera…
极紫外光变率实验（EVE）在太阳耀斑期间观测到的Fe XVI 33.5 nm谱线辐照度的第二个峰值被称为极紫外光（EUV）晚期相。我们之前的论文（Liu et al. 2013）发现，晚期阶段的主要排放来自与后耀斑环（PFL）密切相关但不同的大规模环弧，我们还提出，没有额外加热的长期冷却过程可以解释晚期阶段。在本文中，我们定义了极大的后期阶段，因为它不仅在温暖的33.5辐照度轮廓中具有更大的峰值，而且比主阶段释放更多的EUV辐射能量。从三个角度对极紫外图像进行了详细的分析，发现除了后期的相位环弧外，后期的巨大相位弧的贡献主要来自于一个未喷发的热结构。这种热结构被认为是一个通量绳，它很快被耀斑重联所激励，然后在渐变阶段持续产生热能。未喷发的磁通绳与附加加热一起与后期环路拱廊一起产生了极大的EUV后期。
We present millimeter, optical, and soft X-ray observations of a stellar flare with an energy squarely in the regime of typical X1 solar flares. The flare was observed from Proxima Cen on 2019 May 6 as part of a larger multi-wavelength flare monitoring campaign and was captured by Chandra, LCOGT, du Pont, and ALMA. Millimeter emission appears to be a common occurrence in small stellar flares that had gone undetected until recently, making it difficult to interpret these events within the current multi-wavelength picture of the flaring process. The May 6 event is the smallest stellar millimeter…
Extremely Large Extreme-ultraviolet Late Phase Powered by Intense Early Heating in a Non-eruptive Solar Flare
我们分析并模拟了2011年9月9日发生的M1.2级非爆发性太阳耀斑。耀斑具有强的极紫外暖日冕发射（$\sim$ 3~MK）的晚相峰，峰值发射是主耀斑峰值的1.3倍以上。观测到多个耀斑带，其演化过程表现为两个阶段的能量释放过程。一个非线性无力场（NLFFF）外推揭示了存在一个磁零点，一个扇脊结构，和两个磁通绳嵌入在扇圆顶。耀斑中的磁重联是由其中一条磁通绳的不稳定和上升驱动的。在第一阶段，快速上升的磁通绳驱动在零点和周围的准分界线层（QSL）的重联，而在第二阶段，重联主要发生在最终停止的磁通绳拉伸的两个腿之间的场线。晚期相环主要由第一级QSL重联产生，而第二级重联则负责加热主耀斑环。第一阶段的重联被认为是更强大的，导致一个非常强大的EUV后期。我们发现，延迟出现的晚相峰主要是由于长的晚相环的冷却过程长。使用基于热演化的环路模型（EBTEL），我们模拟了后期环路的EUV辐射。模拟结果表明，后期回路的峰值加热速率为1.1 erg cm $^{-3}$ s $^{-1}$，明显高于以往的数值。
White-light flares are magnetically driven localized brightenings on the surfaces of stars. Their temporal, spectral, and statistical properties present a treasury of physical information about stellar magnetic fields. The spatial distributions of magnetic spots and associated flaring regions help constrain dynamo theories. Moreover, flares are thought to crucially affect the habitability of exoplanets that orbit these stars. Measuring the location of flares on stars other than the Sun is challenging due to the lack of spatial resolution. Here we present four fully convective stars observed wi…
In this multi-instrument paper, we search for evidence of sustained magnetic reconnection far beyond the impulsive phase of the X8.2-class solar flare on 2017 September 10. Using Hinode/EIS, CoMP, SDO/AIA, K-Cor, Hinode/XRT, RHESSI, and IRIS, we study the late-stage evolution of the flare dynamics and topology, comparing signatures of reconnection with those expected from the standard solar flare model. Examining previously unpublished EIS data, we present the evolution of non-thermal velocity and temperature within the famous plasma sheet structure, for the first four hours of the flare's dur…
Solar flares are occasionally responsible for severe Space Weather events, which can affect space-borne and ground-based infrastructures, endangering anthropic technological activities and even human health and safety. Thus, an essential activity in the framework of Space Weather monitoring is devoted to the observation of the activity level of the Sun. In this context, the acquisition system of the Catania Solar Telescope has been recently upgraded in order to improve its contribution to the European Space Agency (ESA) - Space Weather Service Network through the ESA Portal, which represents t…
