A statistical study of the chromospheric ribbon evolution in H$α$ two-ribbon flares is performed. The data set consists of 50 confined ($62\,\%$) and eruptive ($38\,\%$) flares that occurred from June 2000 to June 2015. The flares are selected homogeneously over the H$α$ and $\textit{GOES}$ (Geostationary Operational Environmental Satellite) classes, with an emphasis on including powerful confined flares and weak eruptive flares. H$α$ filtergrams from Kanzelhöhe Observatory in combination with $\textit{MDI}$ (Michelson Doppler Imager) and $\textit{HMI}$ (Helioseismic and Magnetic Imager) magnetograms are used to derive the ribbon separation, the ribbon-separation velocity, the magnetic-field strength, and the reconnection electric field. We find that eruptive flares reveal statistically larger ribbon separation and higher ribbon-separation velocities than confined flares. In addition, the ribbon separation of eruptive flares correlates with the GOES SXR flux, whereas no clear dependence was found for confined flares. The maximum ribbon-separation velocity is not correlated with the GOES flux, but eruptive flares reveal on average a higher ribbon-separation velocity (by $\approx 10~$km$~$s$^{-1}$). The local reconnection electric field of confined ($cc=0.50~\pm~0.02$) and eruptive ($cc=0.77~\pm~0.03$) flares correlates with the GOES flux, indicating that more powerful flares involve stronger reconnection electric fields. In addition, eruptive flares with higher electric-field strengths tend to be accompanied by faster coronal mass ejections.
We report multi-wavelength study of a complex M-class solar eruptive flare that consists of three different sets of flare ribbons, viz. circular, parallel, and remote ribbons. Magnetic field modeling of source active region NOAA 12242 exhibits the presence of 3D null-point magnetic topology which encompasses an inner bipolar region. The event initiates with the faint signatures of the circular ribbon along with remote brightening right from the pre-flare phase which points toward the ongoing slow yet persistent null-point reconnection. We first detected flux cancellation and an associated brig…
Solar flares are one of the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ejection, both of which are probably driven by the eruption of a magnetic flux rope (MFR). Here we report an eruptive flare on 2016 March 23 observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The extreme-ultraviolet imaging observations exhibit the clear rise and eruption of an MFR. In particular, the observations reveal solid evidence for mag…
On 23 July 2016 after 05:00\,UTC, the first 48-antenna stage of the Siberian Radioheliograph detected two flares of M7.6 and M5.5 GOES importance that occurred within half an hour in the same active region. Their multi-instrument analysis reveals the following. The microwave spectra were flattened at low frequencies and the spectrum of the stronger burst had a lower turnover frequency. Each flare was eruptive, emitted hard X-rays and gamma-rays exceeding 800\,keV, and had a rare three-ribbon configuration. An extended hard X-ray source associated with a longest middle ribbon was observed in th…
We study an eruptive X1.1 circular-ribbon flare on 2013 November 10, combining multiwavelength observations with a coronal field reconstruction using a non-force-free field method. In the first stage, a filament forms via magnetic reconnection between two mildly twisted sheared arcades, which are embedded under the fan dome associated with a null point. This reconnection seems to be driven by photospheric shearing and converging flows around the inner two arcade footpoints, consistent with the flare-related changes of transverse field. The southern portion of the filament rises upward due to t…
We report evolution of an atypical X-shaped flare ribbon which provides novel observational evidence of three-dimensional (3D) magnetic reconnection at a separator. The flare occurred on 2014 November 9. High-resolution slit-jaw 1330 A images from the Interface Region Imaging Spectrograph reveal four chromospheric flare ribbons that converge and form an X-shape. Flare brightening in the upper chromosphere spreads along the ribbons toward the center of the "X" (the X-point), and then spreads outward in a direction more perpendicular to the ribbons. These four ribbons are located in a quadrupola…
Low-temperature plasma ejected in solar eruptions can screen active regions as well as quiet solar areas. Absorption phenomena can be observed in microwaves as 'negative bursts' and in different spectral domains. We analyze two very different recent events with such phenomena and present an updated systematic view of solar events associated with negative bursts. Related filament eruptions can be normal, without essential changes of shape and magnetic configuration, and 'anomalous'. The latter are characterized by disintegration of an eruptive filament and dispersal of its remnants as a cloud o…
We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform magnetic flux sheet was injected into a fully developed convective layer. The gradual emergence of the field into the solar atmosphere results in a network of magnetic loops, which interact dynamically forming current layers at their interfaces. The formation and ejection of plasmoids out of the current layers leads to patchy reconnection and the spontaneous formation …
Solar eruptive events such as coronal mass ejections and eruptive flares are frequently associated with the emergence of magnetic flux from the convection zone into the corona. We use three dimensional magnetohydrodynamic numerical simulations to study the interaction of coronal magnetic fields with emerging flux and determine the conditions that lead to eruptive activity. A simple parameter study is performed, varying the relative angle between emerging magnetic flux and a pre-existing coronal dipole field. We find that in all cases, the emergence results in a sheared magnetic arcade that tra…
We studied the background field for 60 two-ribbon flares of M-and-above classes during 2011--2015. These flares are categorized into two groups, i.e., \emph{eruptive} and \emph{confined} flares, based on whether a flare is associated with a coronal mass ejection or not. The background field of source active regions is approximated by a potential field extrapolated from the $B_z$ component of vector magnetograms provided by the Helioseismic and Magnetic Imager. We calculated the decay index $n$ of the background field above the flaring polarity inversion line, and defined a critical height $h_\…
Using the HMI/SDO vector magnetic field observations, we studied the relation of degree of magnetic non-potentiality with the observed flare/CME in active regions. From a sample of 77 flare/CME cases, we found a general relation that degree of non-potentiality is positively correlated with the flare strength and the associated CME speeds. Since the magnetic flux in the flare-ribbon area is more related to the reconnection, we trace the strong gradient polarity inversion line (SGPIL), Schrijver's R value manually along the flare-ribbon extent. Manually detected SGPIL length and R values show hi…
Multiwavelength Observations of the Precursors Before the Eruptive X4.9 Limb Solar Flare on 25 February, 2014: Current Sheet, Eruptive Filament, Flare and Eruption Onset in the Frame of the Tether-Cutting Magnetic Reconnection Scenario
We present a database of 3137 solar flare ribbon events corresponding to every flare of GOES class C1.0 and greater within 45 degrees from the central meridian, from April 2010 until April 2016, observed by the \emph{Solar Dynamics Observatory}. For every event in the database, we compare the GOES peak X-ray flux with corresponding active-region and flare-ribbon properties. We find that while the peak X-ray flux is not correlated with the active region unsigned magnetic flux, it is strongly correlated with the flare ribbon reconnection flux, flare ribbon area, and the fraction of active region…
We study the energy release process of a set of 51 flares (32 confined, 19 eruptive) ranging from GOES class B3 to X17. We use H$α$ filtergrams from Kanzelhöhe Observatory together with SDO HMI and SOHO MDI magnetograms to derive magnetic reconnection fluxes and rates. The flare reconnection flux is strongly correlated with the peak of the GOES 1-8 Å soft X-ray flux (c=0.92, in log-log space), both for confined and eruptive flares. Confined flares of a certain GOES class exhibit smaller ribbon areas but larger magnetic flux densities in the flare ribbons (by a factor of 2). In the largest even…
The nature of three-dimensional reconnection when a twisted flux tube erupts during an eruptive flare or coronal mass ejection is considered. The reconnection has two phases: first of all, 3D "zipper reconnection" propagates along the initial coronal arcade, parallel to the polarity inversion line (PIL), then subsequent quasi-2D "main phase reconnection" in the low corona around a flux rope during its eruption produces coronal loops and chromospheric ribbons that propagate away from the PIL in a direction normal to it. One scenario starts with a sheared arcade: the zipper reconnection creates …
Large-scale solar eruptive activities have a close relationship with coronal magnetic flux ropes. Previous numerical studies have found that the equilibrium of a coronal flux rope system could be disrupted if the axial magnetic flux of the rope exceeds a critical value, so that the catastrophe occurs, initiating the flux rope to erupt. Further studies discovered that the catastrophe does not necessarily exist: the flux rope system with certain photospheric flux distributions could be non-catastrophic. It is noteworthy that most previous numerical studies are under the ideal magnetohydrodynamic…
With the observations of the Solar Dynamics Observatory, we present the slipping magnetic reconnections with multiple flare ribbons (FRs) during an X1.2 eruptive flare on 2014 January 7. A center negative polarity was surrounded by several positive ones, and there appeared three FRs. The three FRs showed apparent slipping motions, and hook structures formed at their ends. Due to the moving footpoints of the erupting structures, one tight semi-circular hook disappeared after the slippage along its inner and outer edge, and coronal dimmings formed within the hook. The east hook also faded as a r…
A standard model for eruptive flares aims at describing observational 3D features of the reconnecting coronal magnetic field. Extensions to the 2D model require the physical understanding of 3D reconnection processes at the origin of the magnetic configuration evolution. However, the properties of 3D reconnection without null point and separatrices still need to be analyzed. We focus on magnetic reconnection associated with the growth and evolution of a flux rope and associated flare loops during an eruptive flare. We aim at understanding the intrinsic characteristics of 3D reconnection in the…
One of the major discoveries of Hinode's Extreme-ultraviolet Imaging Spectrometer (EIS) is the presence of upflows at the edges of active regions. As active regions are magnetically connected to the large-scale field of the corona, these upflows are a likely contributor to the global mass cycle in the corona. Here we examine the driving mechanism(s) of the very strong upflows with velocities in excess of 70 km/s, known as blue-wing asymmetries, observed during the eruption of a flux rope in AR 10977 (eruptive flare SOL2007-12-07T04:50). We use Hinode/EIS spectroscopic observations combined wit…
In this article, we measure the mean magnetic shear from the morphological evolution of flare ribbons, and examine the evolution of flare thermal and non-thermal X-ray emissions during the progress of flare reconnection. We analyze three eruptive flares and three confined flares ranging from GOES class C8.0 to M7.0. They exhibit well-defined two ribbons along the magnetic polarity inversion line (PIL), and have been observed by the Atmospheric Imaging Assembly and the Ramaty High Energy Solar Spectroscopic Imager from the onset of the flare throughout the impulsive phase. The analysis confirms…
We present the quasi-periodic slipping motion of flux rope structures prior to the onset of an eruptive X-class flare on 2015 March 11, obtained by the \emph{Interface Region Imaging Spectrograph} (\emph{IRIS}) and the \emph{Solar Dynamics Observatory} (\emph{SDO}). The slipping motion occurred at the north part of the flux rope and seemed to successively peel off the flux rope. The speed of the slippage was 30$-$40 km s$^{-1}$, with an average period of 130$\pm$30 s. The Si {\sc iv} 1402.77 Å line showed a redshift of 10$-$30 km s$^{-1}$ and a line width of 50$-$120 km s$^{-1}$ at the west le…
The disintegration of solar filaments via mass drainage is a frequently observed phenomenon during a variety of filament activities. It is generally considered that the draining of dense filament material is directed by both gravity and magnetic field, yet the detailed process remains elusive. Here we report on a partial filament eruption during which filament material drains downward to the surface not only along the filament's legs, but to a remote flare ribbon through a fan-out curtain-like structure. It is found that the magnetic configuration is characterized by two conjoining dome-like q…
During eruptive solar flares and coronal mass ejections, a non-pot{\-}ential magnetic arcade with much excess magnetic energy goes unstable and reconnects. It produces a twisted erupting flux rope and leaves behind a sheared arcade of hot coronal loops. We suggest that: the twist of the erupting flux rope can be determined from conservation of magnetic flux and magnetic helicity and equipartition of magnetic helicity. It depends on the geometry of the initial pre-eruptive structure. Two cases are considered, in the first of which a flux rope is not present initially but is created during the e…
We analyze a unique event with an M1.8 confined circular-ribbon flare on 2016 February 13, with successive formations of two circular ribbons at the same location. The flare had two distinct phases of UV and EUV emissions with an interval of about 270 s, of which the second peak was energetically more important. The first episode was accompanied by the eruption of a mini-filament and the fast elongation motion of a thin circular ribbon (CR1) along the counterclockwise direction at a speed of about 220 km/s. Two elongated spine-related ribbons were also observed, with the inner ribbon co-tempor…
In this paper, we present a multi-wavelength analysis of an eruptive white-light M3.2 flare which occurred in active region NOAA 10486 on November 1, 2003. Excellent set of high resolution observations made by RHESSI and TRACE provide clear evidence of significant pre-flare activities for ~9 minutes in the form of an initiation phase observed at EUV/UV wavelengths followed by the X-ray precursor phase. During the initiation phase, we observed localized brightenings in the highly sheared core region close to the filament and interactions among short EUV loops overlying the filament which led to…
Automatic detection of Flare Ribbon Fine Structures as Proxies for Plasmoid Dynamics in Flare Reconnection
Department of Mathematical Sciences, Durham University（达勒姆大学数学科学系）；Heliophysics Science Division, NASA Goddard Space Flight Center（NASA戈达德太空飞行中心日球物理学部）；Astronomy Department, University of Maryland, College Park（马里兰大学天文学系）；Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Glasgow（格拉斯哥大学物理与天文学学院苏格兰大学物理联盟）；Rosseland Centre for Solar Physics, University of Oslo（奥斯陆大学罗瑟兰太阳物理学中心）
This paper studies the magnetic topology of successively erupting active regions (ARs) 11429 and 12371. Employing vector magnetic field observations from Helioseismic and Magnetic Imager, the pre-eruptive magnetic structure is reconstructed by a model of non-linear force-free field (NLFFF). For all the five CMEs from these ARs, the pre-eruptive magnetic structure identifies an inverse-S sigmoid consistent with the coronal plasma tracers in EUV observations. In all the eruption cases, the quasi-separatrix layers (QSLs) of Large Q values are continuously enclosing core field bipolar regions in w…
We analyzed and modeled an M1.2 non-eruptive solar flare on 2011 September 9. The flare exhibits a strong late-phase peak of the warm coronal emissions ($\sim$3~MK) of extreme-ultraviolet (EUV), with peak emission over 1.3 times that of the main flare peak. Multiple flare ribbons are observed, whose evolution indicates a two-stage energy release process. A non-linear force-free field (NLFFF) extrapolation reveals the existence of a magnetic null point, a fan-spine structure, and two flux ropes embedded in the fan dome. Magnetic reconnections involved in the flare are driven by the destabilizat…
Magnetic reconnection is believed to be the prime mechanism to trigger solar flares and accelerate electrons up to energies of MeV. In the classical two-dimensional reconnection model, the separation motion of chromospheric ribbons manifests the successive reconnection that takes place higher up in the corona. Meanwhile, downward traveling energetic electrons bombard the dense chromosphere and create hard X-ray (HXR) emissions, which provide a valuable diagnostic of electron acceleration. Analyses of ribbon dynamics and HXR spectrum have been carried out separately. In this Letter, we report a…
In this paper, we present observations and analysis of an interesting sigmoid formation, eruption and the associated flare that occurred on 2014 April 18 using multi-wavelength data sets. We discuss the possible role of the sigmoid eruption in triggering the flare, which consists of two different set of ribbons: parallel ribbons as well as a large-scale quasi-circular ribbon. Several observational evidence and nonlinear force-free field extrapolation results show the existence of a large-scale fan-spine type magnetic configuration with a sigmoid lying under a section of the fan dome. The event…
We present AIA observations of a structure we interpret as a current sheet associated with an X4.9 flare and coronal mass ejection that occurred on 2014~February~25 in NOAA Active Region 11990. We characterize the properties of the current sheet, finding that the sheet remains on the order of a few thousand km thick for much of the duration of the event and that its temperature generally ranged between $8-10\,\mathrm{MK}$. We also note the presence of other phenomena believed to be associated with magnetic reconnection in current sheets, including supra-arcade downflows and shrinking loops. We…
A solar jet on 2014 July 31, which was accompanied by a GOES C1.3 flare and a mini-filament eruption at the jet base, was studied by using observations taken by the New Vacuum Solar Telescope and the Solar Dynamic Observatory. Magnetic field extrapolation revealed that the jet was confined in a fan-spine magnetic system that hosts a null point at the height of about 9 Mm from the solar surface. An inner flare ribbon surrounded by an outer circular ribbon and a remote ribbon were observed to be associated with the eruption, in which the inner and remote ribbons respectively located at the footp…
We present a detailed study of a confined circular flare dynamics associated with 3 UV late phases in order to understand more precisely which topological elements are present and how they constrain the dynamics of the flare. We perform a non-linear force free field extrapolation of the confined flare observed with the HMI and AIA instruments onboard SDO. From the 3D magnetic field we compute the squashing factor and we analyse its distribution. Conjointly, we analyse the AIA EUV light curves and images in order to identify the post-flare loops, their temporal and thermal evolution. By combini…
In this article, we review some key aspects of a multi-wavelength flare which have essentially contributed to form a standard flare model based on the magnetic reconnection. The emphasis is given on the recent observations taken by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on the X-ray emission originating from different regions of the coronal loops. We also briefly summarize those observations which do not seem to accommodate within the canonical flare picture and discuss the challenges for future investigations.
Utilizing multiwavelength observations and magnetic field data from SDO/AIA, SDO/HMI, GOES and RHESSI, we investigate a large-scale ejective solar eruption of 2014 December 18 from active region NOAA 12241. This event produced a distinctive three-ribbon flare, having two parallel ribbons corresponding to the ribbons of a standard two-ribbon flare, and a larger-scale third quasi-circular ribbon offset from the other two ribbons. There are two components to this eruptive event. First, a flux rope forms above a strong-field polarity-inversion line and erupts and grows as the parallel ribbons turn…
We study a complex GOES M1.1 circular ribbon flare and related pre-flare activity on 26 January 2015 [SOL26-01-2015] in solar active region NOAA 12268. This flare activity was observed by the AIA on board SDO and the RHESSI. The examination of photospheric magnetograms during the extended period, prior to the event, suggests the successive development of a so-called 'anemone' type magnetic configuration. NLFFF extrapolation reveals a fan-spine magnetic configuration with the presence of a coronal null-point. We found that the pre-flare activity in the active region starts ~15 min prior to the …
The solar corona is frequently disrupted by coronal mass ejections (CMEs), whose core structure is believed to be a flux rope made of helical magnetic field. This has become a "standard" picture although it remains elusive how the flux rope forms and evolves toward eruption. While 1/3 of the ejecta passing through spacecrafts demonstrate a flux-rope structure, the rest have complex magnetic fields. Are they originating from a coherent flux rope, too? Here we investigate the source region of a complex ejecta, focusing on a flare precursor with definitive signatures of magnetic reconnection, i.e…
Sunward-flowing voids above post-coronal mass ejection (CME) flare arcades were first discovered using the soft X-ray telescope (SXT) aboard Yohkoh and have since been observed with TRACE (extreme ultra-violet (EUV)), SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (soft X-rays (SXR)). Supra-arcade downflow (SAD) observations suggest that they are the cross-sections of thin flux tubes retracting from a reconnection site high in the corona. Supra-arcade downflowing loops (SADLs) have also been observed under similar circumstances and are theorized to be SADs viewed from a per…
We firstly report the quasi-periodic slipping motion of flare loops during an eruptive X-class flare on 2014 September 10. The slipping motion was investigated at a specific location along one of the two ribbons and can be observed throughout the impulsive phase of the flare. The apparent slipping velocity was 20-110 km/s and the associated period was 3$-$6 min. The footpoints of flare loops appeared as small-scale bright knots observed in 1400 Å, corresponding to fine structures of the flare ribbon. These bright knots were observed to move along the southern part of the longer ribbon and also…
We studied a circular-ribbon flare, SOL2014-12-17T04:51, with emphasis on its thermal evolution as determined by the Differential Emission Measure (DEM) inversion analysis of the extreme ultraviolet (EUV) images of the Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO). Both temperature and emission measure start to rise much earlier than the flare, along with an eruption and formation of a hot halo over the fan structure. In the main flare phase, another set of ribbons forms inside the circular ribbon, and expands as expected for ribbons at the footpoin…
n order to better understand the solar genesis of interplanetary magnetic clouds (MCs) we model the magnetic and topological properties of four large eruptive solar flares and relate them to observations. We use the three-dimensional Minimum Current Corona model \cite{Longcope1996d} and observations of pre-flare photospheric magnetic field and flare ribbons to derive values of reconnected magnetic flux, flare energy, flux rope helicity and orientation of the flux rope poloidal field. We compare model predictions of those quantities to flare and MC observations and within the estimated uncertai…
We study the magnetic field structures of hard X-ray sources and flare ribbons of the M1.1 flare in active region NOAA 10767 on 2005 May 27. We have found in a nonlinear force-free field extrapolation, over the same polarity inversion line, a small pre-eruptive magnetic flux rope located next to sheared magnetic arcades. Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Transition Region and Coronal Explorer (TRACE) observed this confined flare in the X-ray bands and ultraviolet (UV) 1600 Å\ bands, respectively. In this event magnetic reconnection occurred at several locations. It fir…
Magnetic reconnection is a well-accepted part of the theory of solar eruptive events, though the evidence is still circumstantial. Intrinsic to the reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares ("CSHKP" model), are an advective flow of magnetized plasma into the reconnection region, expansion of field above the reconnection region as a flux rope erupts, retraction of heated post-reconnection loops, and downflows of cooling plasma along those loops. We report on a unique set of SDO/AIA imaging and Hinode/EIS spectroscopic observations o…
We present an extensive analysis of the X2.0-class confined flare on 2014 October 27 in the great active region AR 12192, observed by the \emph{Interface Region Imaging Spectrograph} and the \emph{Solar Dynamics Observatory}. The slipping motion of the substructures within the negative-polarity flare ribbon (R1) and continual reconnection-induced flows during the confined flare are first presented. The substructures within ribbon R1 were observed to slip in opposite directions at apparent speeds of 10-70 km s$^{-1}$. The slipping motion exhibited the quasi-periodic pattern with a period of 80-…
We present high resolution 2.5-dimensional MHD simulation results of magnetic breakout-initiated coronal mass ejections (CMEs) originating from a coronal pseudostreamer configuration. The coronal null point in the magnetic topology of pseudostreamers means the initiation of consecutive sympathetic eruptions is a natural consequence of the system's evolution. A generic source region energization process -- ideal footpoint shearing parallel to the pseudostreamer arcade polarity inversion lines -- is all that is necessary to store sufficient magnetic energy to power consecutive CME eruptions give…
We present an analysis of the apparent elongation motion of flare ribbons along the polarity inversion line (PIL) as well as the shear of flare loops in several two-ribbon flares. Flare ribbons and loops spread along the PIL at a speed ranging from a few to a hundred km/s. The shear measured from conjugate foot-points is consistent with the measurement from flare loops, and both show the decrease of shear toward a potential field as a flare evolves and ribbons and loops spread along the PIL. Flares exhibiting fast bi-directional elongation appear to have a strong shear, which may indicate a la…
The chapter "Solar Active Region Electric Currents Before and During Eruptive Flares" is a discussion on electric currents in the pre-eruption state and in the course of eruptions of solar magnetic structures, using information from solar observations, nonlinear force-free field extrapolations relying on these observations, and three-dimensional magnetohydrodynamic (MHD) models. The discussion addresses the issue of neutralized vs. non-neutralized currents in active regions and concludes that MHD models are able to explain non-neutralized currents in active regions by the existence of strong m…
Researchers have reported (i) correlations of coronal mass ejection (CME) speeds and the total photospheric magnetic flux swept out by flare ribbons in flare-associated eruptive events, and, separately, (ii) correlations of CME speeds and more rapid decay, with height, of magnetic fields in potential coronal models above eruption sites. Here, we compare the roles of both ribbon fluxes and the decay rates of overlying fields in a set of 16 eruptive events. We confirm previous results that higher CME speeds are associated with both larger ribbon fluxes and more rapidly decaying overlying fields.…
The Association of Solar Radio Bursts with Eruptive and Confined Flares
Space Warfare Directorate, Air Force Research Laboratory（太空作战司令部，空军研究实验室）；University of New Mexico（新墨西哥大学）；University of Colorado, Boulder（科罗拉多大学博尔德分校）；National Solar Observatory（国家太阳观测台）
We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare which begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by SDO/AIA can be well reproduced from a Grad-Rubin non linear force free field extrapolation method. Various inverse-S and -J shaped magnetic field lines, that surround a coronal flux rope, coincide with the sigmoid as observed in different extreme ultraviolet wavelengths, including its multi-threaded curve…
Unprecedent fast winking of solar flares triggered by bursty magnetic reconnection
National Space Science Center, Chinese Academy of Sciences（中国科学院国家空间科学中心）；University of Chinese Academy of Sciences（中国科学院大学）；Observatoire de Paris-PSL（巴黎天文台-PSL）；Institut Polytechnique de Paris（巴黎理工学院）；CNRS（法国国家科学研究中心）；Laboratoire de physique des plasmas (LPP)（等离子体物理实验室）；Rosseland Center for Solar Physics, University of Oslo（奥斯陆大学罗斯兰太阳物理学中心）；Institute of Theoretical Astrophysics, University of Oslo（奥斯陆大学理论天体物理研究所）；Space Research Institute of the Russian Academy of Sciences (IKI)（俄罗斯科学院太空研究所）；Anhui University（安徽大学）；Bay Area Environmental Research Institute, NASA Research Park（NASA研究园湾区环境研究所）；Lockheed Martin Solar and Astrophysics Laboratory（洛马太阳与天体物理实验室）；Institute of Solar-Terrestrial Physics SB RAS（西伯利亚分支俄罗斯科学院太阳地球物理研究所）；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；Nanjing University（南京大学）；Macau University of Science and Technology（澳门科技大学）
