arXiv subjects

Leping Li

Publications and source records attributed to Leping Li.

At least 37 records · Page 2Linked to original sources

arXiv2022

A partial filament eruption in three steps induced by external magnetic reconnection

We present an investigation of partial filament eruption on 2012 June 17 in the active region NOAA 11504. For the first time, we observed the vertical splitting process during the partial eruption with high resolution narrow band images at 10830 . The active filament was rooted in a small sunspot of the active region. Particularly, it underwent the partial eruption in three steps, i.e. the precursor, the first eruption, and the second eruption, while the later two were associated with a C1.0 flare and a C3.9 flare, respectively. During the precursor, slow magnetic reconnection took place between the filament and the adjoining loops that also rooted in the sunspot. The continuous reconnection not only caused the filament to split into three groups of threads vertically but also formed a new filament, which was growing and accompanied brightening took place around the site. Subsequently, the growing filament erupted together with one group splitted threads, resulted in the first eruption. At the beginning of the first eruption, a subsequent magnetic reconnection occurred between the erupting splitted threads and another ambient magnetic loop. After about three minutes, the second eruption occurred as a result of the eruption of two larger unstable filaments induced by the magnetic reconnection. The high-resolution observation provides a direct evidence that magnetic reconnection between filament and its ambient magnetic fields could induce the vertical splitting of the filament, resulting in partial eruption.

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arXiv2021

Coronal Condensation as the Source of Transition Region Supersonic Downflows above a Sunspot

Plasma loops or plumes rooted in sunspot umbrae often harbor downflows with speeds of 100 km/s. These downflows are supersonic at transition region temperatures of 0.1 MK. The source of these flows is not well understood. We aim to investigate the source of sunspot supersonic downflows (SSDs) in AR 12740 using simultaneous spectroscopic and imaging observations. We identified SSD events from multiple raster scans of a sunspot by the Interface Region Imaging Spectrograph, and calculated the electron densities, mass fluxes and velocities of these SSDs. The EUV images provided by the AIA onboard the SDO and the EUVI onboard the STEREO were employed to investigate the origin of these SSDs and their associated coronal rain. Almost all the identified SSDs appear at the footpoints of sunspot plumes and are temporally associated with appearance of chromospheric bright dots inside the sunspot umbra. Dual-perspective EUV imaging observations reveal a large-scale closed magnetic loop system spanning the sunspot region and a remote region. We observed that the SSDs are caused by repeated coronal rain that forms and flows along these closed magnetic loops toward the sunspot. One episode of coronal rain clearly indicates that reconnection near a coronal X-shaped structure first leads to the formation of a magnetic dip. Subsequently, hot coronal plasma catastrophically cools from 2 MK in the dip region via thermal instability. This results in the formation of a transient prominence in the dip, from which the cool gas mostly slides into the sunspot along inclined magnetic fields under the gravity. This drainage process manifests as a continuous rain flow, which lasts for around 2 hrs and concurrently results in a nearly steady SSD event. Our results demonstrate that coronal condensation in magnetic dips can result in the quasi-steady sunspot supersonic downflows.

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arXiv2021

Comparison of Helium Abundance between ICMEs and Solar Wind near 1 AU

The Helium abundance, defined as $A_{He}=n_{He}/n_{H}\times 100$, is $\sim$8.5 in the photosphere and seldom exceeds 5 in fast solar wind. Previous statistics have demonstrated that $A_{He}$ in slow solar wind correlates tightly with sunspot number. However, less attention is paid to the solar cycle dependence of $A_{He}$ within interplanetary coronal mass ejections (ICMEs) and comparing the $A_{He}$ characteristics of ICMEs and solar wind. In this paper we conduct a statistical comparison of Helium abundance between ICMEs and solar wind near 1 AU with observations of \textit{Advanced Composition Explorer} from 1998 to 2019, and find that the ICME $A_{He}$ also exhibits the obvious solar cycle dependence. Meanwhile, we find that the $A_{He}$ is obviously higher within ICMEs compared to solar wind, and the means within 37\% and 12\% of ICMEs exceed 5 and 8.5, respectively. It is interesting to answer where and how the high Helium abundance originates. Our statistics demonstrate that 21\% (3\%) of ICME (slow wind) $A_{He}$ data points exceed 8.5 around solar maximum, which decreases dramatically near minimum, while no such high $A_{He}$ values appear in the fast wind throughout the whole solar cycle. This indicates that the high $A_{He}$ (e.g., $>$8.5) emanates from active regions as more ICMEs and slow wind originates from active regions around maximum, and supports that both active regions and quiet-Sun regions are the sources of slow wind. We suggest that the high $A_{He}$ from active regions could be explained by means of the magnetic loop confinement model and/or photoionization effect.

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arXiv2021

Formation of a solar filament by magnetic reconnection and coronal condensation

In solar filament formation mechanisms, magnetic reconnection between two sets of sheared arcades forms helical structures of the filament with numerous magnetic dips, and cooling and condensation of plasma trapped inside the helical structures supply mass to the filament. Although each of these processes, namely, magnetic reconnection and coronal condensation have been separately reported, observations that show the whole process of filament formation are rare. In this Letter, we present the formation of a sigmoid via reconnection between two sets of coronal loops, and the subsequent formation of a filament through cooling and condensation of plasma inside the newly formed sigmoid. On 2014 August 27, a set of loops in the active region 12151 reconnected with another set of loops that are located to the east. A longer twisted sigmoidal structure and a set of shorter lower-lying loops then formed. The observations coincide well with the tether-cutting model. The newly formed sigmoid remains stable and does not erupt as a coronal mass ejection. From the eastern endpoint, signatures of injection of material into the sigmoid (as brightenings) are detected, which closely outline the features of increasing emission measure at these locations. This may indicate the chromospheric evaporation caused by reconnection, supplying heated plasma into the sigmoid. In the sigmoid, thermal instability occurs, and rapid cooling and condensation of plasma take place, forming a filament. The condensations then flow bi-directionally to the filament endpoints. Our results provide a clear observational evidence of the filament formation via magnetic reconnection and coronal condensation.

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arXiv2021

A Hybrid Approach to Fine-grained Automated Fault Localization

Fault localization is to identify faulty source code. It could be done on various granularities, e.g., classes, methods, and statements. Most of the automated fault localization (AFL) approaches are coarse-grained because it is challenging to accurately locate fine-grained faulty software elements, e.g., statements. SBFL, based on dynamic execution of test cases only, is simple, intuitive, and generic (working on various granularities). However, its accuracy deserves significant improvement. To this end, in this paper, we propose a hybrid fine-grained AFL approach based on both dynamic spectrums and static statement types. The rationale of the approach is that some types of statements are significantly more/less error-prone than others, and thus statement types could be exploited for fault localization. On a crop of faulty programs, we compute the error-proneness for each type of statements, and assign priorities to special statement types that are steadily more/less error-prone than others. For a given faulty program under test, we first leverage traditional spectrum-based fault localization algorithm to identify all suspicious statements and to compute their suspicious scores. For each of the resulting suspicious statements, we retrieve its statement type as well as the special priority associated with the type. The final suspicious score is the product of the SBFL suspicious score and the priority assigned to the statement type. A significant advantage of the approach is that it is simple and intuitive, making it efficient and easy to interpret/implement. We evaluate the proposed approach on widely used benchmark Defects4J. The evaluation results suggest that the proposed approach outperforms widely used SBFL, reducing the absolute waste effort (AWE) by 9.3% on average.

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arXiv2021

Revisiting the formation mechanism for coronal rain from previous studies

Solar coronal rain is classified generally into two categories: flare-driven and quiescent coronal rain. The latter is observed to form along both closed and open magnetic field structures. Recently, we proposed that some of the quiescent coronal rain events, detected in the transition region and chromospheric diagnostics, along loop-like paths could be explained by the formation mechanism for quiescent coronal rain facilitated by interchange magnetic reconnection between open and closed field lines. In this study, we revisited 38 coronal rain reports from the literature. From these earlier works, we picked 15 quiescent coronal rain events out of the solar limb, mostly suggested to occur in active region closed loops due to thermal nonequilibrium, to scrutinize their formation mechanism. Employing the extreme ultraviolet images and line-of-sight magnetograms, the evolution of the quiescent coronal rain events and their magnetic fields and context coronal structures is examined. We find that 6, comprising 40%, of the 15 quiescent coronal rain events could be totally or partially interpreted by the formation mechanism for quiescent coronal rain along open structures facilitated by interchange reconnection. The results suggest that the quiescent coronal rain facilitated by interchange reconnection between open and closed field lines deserves more attention.

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arXiv2021

The Inhomogeneity of Composition along the Magnetic Cloud Axis

It is generally accepted that CMEs result from eruptions of magnetic flux ropes, which are dubbed as magnetic clouds in interplanetary space. The composition (including the ionic charge states and elemental abundances) is determined prior to and/or during CME eruptions in the solar atmosphere, and does not alter during magnetic cloud propagation to 1 AU and beyond. It has been known that the composition is not uniform within a cross section perpendicular to magnetic cloud axis, and the distribution of ionic charge states within a cross section provides us an important clue to investigate the formation and eruption processes of flux ropes due to the freeze-in effect. The flux rope is a three dimensional magnetic structure intrinsically, and it remains unclear whether the composition is uniform along the flux rope axis as most magnetic clouds are only detected by one spacecraft. In this paper we report a magnetic cloud that was observed by ACE near 1 AU on 1998 March 4--6 and Ulysses near 5.4 AU on March 24--28 sequentially. At these times, both spacecraft were located around the ecliptic plane, and the latitudinal and longitudinal separations between them were $\sim$2.2$^{\circ}$ and $\sim$5.5$^{\circ}$, respectively. It provides us an excellent opportunity to explore the axial inhomogeneity of flux rope composition, as both spacecraft almost intersected the cloud center at different sites along its axis. Our study shows that the average values of ionic charge states exhibit significant difference along the axis for carbon, and the differences are relatively slight but still obvious for charge states of oxygen and iron, as well as the elemental abundances of iron and helium. Besides the means, the composition profiles within the cloud measured by both spacecraft also exhibit some discrepancies. We conclude that the inhomogeneity of composition exists along the cloud axis.

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arXiv2021

Solar Cycle Dependence of ICME Composition

Coronal mass ejections (CMEs) are one of the most energetic explosions in the solar atmosphere, and their occurrence rates exhibit obvious solar cycle dependence with more events taking place around solar maximum. Composition of interplanetary CMEs (ICMEs), referring to the charge states and elemental abundances of ions, opens an important avenue to investigate CMEs. In this paper, we conduct a statistical study on the charge states of five elements (Mg, Fe, Si, C, and O) and the relative abundances of six elements (Mg/O, Fe/O, Si/O, C/O, Ne/O, and He/O) within ICMEs from 1998 to 2011, and find that all the ICME compositions possess the solar cycle dependence. All of the ionic charge states and most of the relative elemental abundances are positively correlated with sunspot numbers (SSNs), and only the C/O ratios are inversely correlated with the SSNs. The compositions (except the C/O) increase with the SSNs during the ascending phase (1998--2000 and 2009--2011) and remain elevated during solar maximum and descending phase (2000--2005) compared to solar minimum (2007--2009). The charge states of low-FIP (first ionization potential) elements (Mg, Fe, and Si) and their relative abundances are correlated well, while no clear correlation is observed between the C$^{6+}$/C$^{5+}$ or C$^{6+}$/C$^{4+}$ and C/O. Most interestingly, we find that the Ne/O ratios of ICMEs and slow solar wind have the opposite solar cycle dependence.

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arXiv2021

On-disk solar coronal condensations facilitated by magnetic reconnection between open and closed magnetic structures

Coronal condensation and rain are a crucial part of the mass cycle between the corona and chromosphere. In some cases, condensation and subsequent rain originate in the magnetic dips formed during magnetic reconnection. This provides a new and alternative formation mechanism for coronal rain. Until now, only off-limb, rather than on-disk, condensation events during reconnection have been reported. In this paper, employing extreme-ultraviolet (EUV) images of the Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory (SDO), we investigate the condensations facilitated by reconnection from 2011 July 14 to 15, when STEREO was in quadrature with respect to the Sun-Earth line. Above the limb, in STEREO/EUV Imager (EUVI) 171 Å~images, higher-lying open structures move downward, reconnect with the lower-lying closed loops, and form dips. Two sets of newly reconnected structures then form. In the dips, bright condensations occur in EUVI 304 Å~images repeatedly which then flow downward to the surface. In the on-disk observations by SDO/Atmospheric Imaging Assembly (AIA) in the 171 Å~channel, these magnetic structures are difficult to identify. Dark condensations appear in AIA 304 Å~images, and then move to the surface as on-disk coronal rain. The cooling and condensation of coronal plasma is revealed by the EUV light curves. If only the on-disk observations would be available, the relation between the condensations and reconnection, shown clearly by the off-limb observations, would not be identified. Thus, we suggest that some on-disk condensation events seen in transition region and chromospheric lines may be facilitated by reconnection.

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arXiv2021

Magnetic reconnection between loops accelerated by a nearby filament eruption

Magnetic reconnection modulated by non-local disturbances in the solar atmosphere has been investigated theoretically, but rarely observed. In this study, employing Ha and extreme ultraviolet (EUV) images and line of sight magnetograms, we report acceleration of reconnection by adjacent filament eruption. In Ha images, four groups of chromospheric fibrils are observed to form a saddle-like structure. Among them, two groups of fibrils converge and reconnect. Two newly reconnected fibrils then form, and retract away from the reconnection region. In EUV images, similar structures and evolution of coronal loops are identified. Current sheet forms repeatedly at the interface of reconnecting loops, with width and length of 1-2 and 5.3-7.2 Mm, and reconnection rate of 0.18-0.3. It appears in the EUV low-temperature channels, with average differential emission measure (DEM) weighed temperature and EM of 2 MK and 2.5*10^27 cm-5. Plasmoids appear in the current sheet and propagate along it, and then further along the reconnection loops. The filament, located at the southeast of reconnection region, erupts, and pushes away the loops covering the reconnection region. Thereafter, the current sheet has width and length of 2 and 3.5 Mm, and reconnection rate of 0.57. It becomes much brighter, and appears in the EUV high-temperature channels, with average DEM-weighed temperature and EM of 5.5 MK and 1.7*10^28 cm-5. In the current sheet, more hotter plasmoids form. More thermal and kinetic energy is hence converted. These results suggest that the reconnection is significantly accelerated by the propagating disturbance caused by the nearby filament eruption.

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arXiv2020

The Formation and Eruption of A Sigmoidal Filament Driven by Rotating Network Magnetic Fields

We present the formation and eruption of a sigmoidal filament driven by rotating network magnetic fields (RNFs) near the center of the solar disk, which was observed by the one-meter aperture New Vacuum Solar Telescope (NVST) at Fuxian Solar Observatory (FSO) on 2018 July 12. Counterclockwise RNFs twist two small-scale filaments at their northeastern foot-point region, giving a rotation of nearly 200 degree within about 140 minutes. The motion of the RNF has a tendency to accelerate at first and then decelerate obviously, as the average rotation speed increased from 10 to 150 ,and then slowed down to 50 . Coalescence then occurs between filaments F1 and F2. Meanwhile the fine structures in the southwestern region of the filament was involved in another interaction of coalescence. The subsequent EUV brightening due to plasma heating is observed in the two interaction regions. These interacting structures, including F1, F2 and the fine structures in the southwestern region, eventually evolve into a larger-scale sigmoidal filament twisted in the same direction as the RNFs gave. The twist of the sigmoidal filament has exceeded 4π and the filament erupted finally. The motion of the sigmoidal filament keeps uniform until a nearby jet collides, causing the filament to erupt faster. These results provide evidence that RNF plays an important role in the formation and eruption of the sigmoidal filament. The phenomena also suggests that the kink instability is the trigger mechanism for the filament eruption.

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arXiv2020

Relation of coronal rain originating from coronal condensations to interchange magnetic reconnection

Using extreme-ultraviolet images, we recently proposed a new and alternative formation mechanism for coronal rain along magnetically open field lines due to interchange magnetic reconnection. In this paper we report coronal rain at chromospheric and transition region temperatures originating from the coronal condensations facilitated by reconnection between open and closed coronal loops. For this, we employ the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). Around 2013 October 19, a coronal rain along curved paths was recorded by IRIS over the southeastern solar limb. Related to this, we found reconnection between a system of higher-lying open features and lower-lying closed loops that occurs repeatedly in AIA images. In this process, the higher-lying features form magnetic dips. In response, two sets of newly reconnected loops appear and retract away from the reconnection region. In the dips, seven events of cooling and condensation of coronal plasma repeatedly occur due to thermal instability over several days, from October 18 to 20. The condensations flow downward to the surface as coronal rain, with a mean interval between condensations of 6.6 hr. In the cases where IRIS data were available we found the condensations to cool all the way down to chromospheric temperatures. Based on our observations we suggest that some of the coronal rain events observed at chromospheric temperatures could be explained by the new and alternative scenario for the formation of coronal rain, where the condensation is facilitated by interchange reconnection.

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arXiv2020

Do All Interplanetary Coronal Mass Ejections Have A Magnetic Flux Rope Structure Near 1 AU?

Interplanetary coronal mass ejections (ICMEs) often consist of a shock wave, sheath region, and ejecta region. The ejecta regions are divided into two broad classes: magnetic clouds (MC) that exhibit the characteristics of magnetic flux ropes and non-magnetic clouds (NMC) that do not. As CMEs result from eruption of magnetic flux ropes, it is important to answer why NMCs do not have the flux rope features. One claims that NMCs lose their original flux rope features due to the interactions between ICMEs or ICMEs and other large scale structures during their transit in the heliosphere. The other attributes this phenomenon to the geometric selection effect, i.e., when an ICME has its nose (flank, including leg and non-leg flanks) pass through the observing spacecraft, the MC (NMC) features will be detected along the spacecraft trajectory within the ejecta. In this Letter, we examine which explanation is more reasonable through the geometric properties of ICMEs. If the selection effect leads to different ejecta types, MCs should have narrower sheath region compared to NMCs from the statistical point of view, which is confirmed by our statistics. Besides, we find that NMCs have the similar size in solar cycles 23 and 24, and NMCs are smaller than MCs in cycle 23 but larger than MCs in cycle 24. This suggests that most NMCs have their leg flank pass through the spacecraft. Our geometric analyses support that all ICMEs should have a magnetic flux rope structure near 1 AU.

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arXiv2019

The dynamics of AR 12700 in its early emerging phase II: fan-shaped activities relevant to arch filament systems

The emergence of active regions (ARs) closely relates to the solar dynamo and the dynamical atmospheric phenomena.With high-resolution and long-lasting observations from the New Vacuum Solar Telescope, we report a new dynamic activity phenomenon named "fan-shaped activity (FSA)" in the emerging phase of NOAA AR 12700. The FSAs are clearly observed at Ha wavelength and are closely related to the dynamics of the adjacent arch filament system (AFS), including threads deformation and materials downward motions. On 2018 February 26, the two most representative FSAs appeared around 05:21 UT and 06:03 UT, respectively, and they firstly ascended and then decayed in around 10 minutes. At the ascending phase, accompanied by the uplifting of an adjacent AFS, each FSA launches up at one end of the AFS and extends for up to 11 Mm. At the decaying phase, the FSA gradually vanishes, and materials downflows towards the other end of the AFS are detected. After checking the evolution of the magnetic fields of AR 12700, we find that each FSA is located between the end of an AFS and an adjacent magnetic patch with the same polarity and launches at the onset of the collision and compression between these two magnetic patches. We propose that the collision lifts up the AFS, and then the initially compact AFS laterally expands, resulting in the formation of FSA. A cartoon model is proposed to depict the activities.

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arXiv2019

Plasma injection into a solar coronal loop

Context. The details of the spectral profiles of extreme UV emission lines from solar active regions contain key information to investigate the structure, dynamics, and energetics of the solar upper atmosphere. Aims. We characterize the line profiles not only through the Doppler shift and intensity of the bulk part of the profile. More importantly, we investigate the excess emission and asymmetries in the line wings to study twisting motions and helicity. Methods. WeusearasterscanoftheInterfaceRegionImagingSpectrograph(IRIS)inanactive region. We concentrate on the Si iv line at 1394 Å that forms just below 0.1 MK and follow the plasma in a cool loop moving from one footpoint to the other. We apply single-Gaussian fits to the line core, determine the excess emission in the red and blue wings, and derive the red-blue line asymmetry. Results. The blue wing excess at one footpoint shows injection of plasma into the loop that is then flowing to the other side. At the same footpoint, redshifts of the line core indicate that energy is deposited at around 0.1 MK. The enhanced pressure would then push down the cool plasma and inject some plasma into the loop. In the middle part of the loop, the spectral tilts of the line profiles indicate the presence of a helical structure of the magnetic field, and the line wings are symmetrically enhanced. This is an indication that the loop is driven through the injection of helicity at the loop feet. Conclusions. Iftheloopisdriventobehelical,thenonecanexpectthatthemagneticfieldwill be in a turbulent state, as it has been shown by existing MHD models. The turbulent motions could provide an explanation of the (symmetric) line wing enhancements which have been seen also in loops at coronal temperatures, but have not been understood so far.

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arXiv2019

Quasi-periodic Fast Propagating Magnetoacoustic Waves during the Magnetic Reconnection Between Solar Coronal Loops

Employing Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) multi-wavelength images, we have presented coronal condensations caused by magnetic reconnection between a system of open and closed solar coronal loops. In this Letter, we report the quasi-periodic fast magnetoacoustic waves propagating away from the reconnection region upward across the higher-lying open loops during the reconnection process. On 2012 January 19, reconnection between the higher-lying open loops and lower-lying closed loops took place, and two sets of newly reconnected loops formed. Thereafter, cooling and condensations of coronal plasma occurred in the magnetic dip region of higher-lying open loops. During the reconnection process, disturbances originating from the reconnection region propagate upward across the magnetic dip region of higher-lying loops with the mean speed and mean speed amplitude of 200 and 30 km s$^{-1}$, respectively. The mean speed of the propagating disturbances decreases from $\sim$230 km s$^{-1}$ to $\sim$150 km s$^{-1}$ during the coronal condensation process, and then increases to $\sim$220 km s$^{-1}$. This temporal evolution of the mean speed anti-correlates with the light curves of the AIA 131 and 304 Å~channels that show the cooling and condensation process of coronal plasma. Furthermore, the propagating disturbances appear quasi-periodically with a peak period of 4 minutes. Our results suggest that the disturbances represent the quasi-periodic fast propagating magnetoacoustic (QFPM) waves originating from the magnetic reconnection between coronal loops.

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arXiv2018

Untwisting and Disintegration of a Solar Filament Associated with Photospheric Flux Cancellation

Using the high-resolution observations from New Vacuum Solar Telescope (NVST) jointly with the Solar Dynamics Observatory data, we investigate two successive confined eruptions (Erup1 and Erup2) of a small filament in a decaying active region on 2017 November 10. During the process of Erup1, the overlying magnetic arcade is observed to inflate with the rising filament at beginning and then stop the ongoing of the explosion. In the hot EUV channel, a coronal sigmoidal structure appears during the first eruption and fade away after the second one. The untwisting rotation and disintegration of the filament in Erup2 are clearly revealed by the NVST H_alpha intensity data, hinting at a pre-existing twisted configuration of the filament. By tracking two rotating features in the filament, the average rotational angular velocity of the unwinding filament is found to be ~10.5 degree/min. A total twist of ~1.3 pi is estimated to be stored in the filament before the eruption, which is far below the criteria for kink instability. In the course of several hours prior to the event, some photospheric flux activities, including the flux convergence and cancellation, are detected around the northern end of the filament, where some small-scale EUV brightenings are also captured. Moreover, strongly-sheared transverse fields are found in the cancelling magnetic features from the vector magnetograms. Our observational results support the flux cancellation model, in which the interaction between the converging and sheared opposite-polarity fluxes destabilizes the filament and triggers the ensuing ejection.

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arXiv2018

Current sheets in the wake of an eruption of two crossing filaments

Employing Solar Dynamic Observatory/Atmosphertic Imaging Assembly (AIA) multi-wavelength images, we study an eruption of two crossing filaments, and firstly report the current sheets (CSs) connecting the lower flare ribbons and the upper erupting filaments. On July 8, 2014, two crossing filaments are observed in the NOAA active region (AR) 12113. The lower-lying filament rises first, and then meets the higher-lying one. Thereafter, both of them erupt together. The filament eruption draws the overlying magnetic field lines upward, leading to the approach of two legs, with opposite magnetic polarities, of the overlying field lines. Two sets of bright CSs form at the interface of these two legs, and magnetic reconnection takes place in the CSs producing the underneath flare ribbons and post-flare loops. Several bright plasmoids appear in the CSs, and propagate along the CSs bi-directionally. The CSs and plasmoids are observed in AIA multi-wavelength channels, indicating that both of them have been heated during the reconnection process, with hot and warm components. Employing the differential emission measure (EM) analysis, we find that both the temperature and EM of the CSs decrease from the flare arcades outward to the erupting filaments, and those of the plasmoids are significantly larger than the regions where no plasmoid is detected.

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