Aiying Duan, Chaowei Jiang, Qiang Hu, Huai Zhang, G. Allen Gary, S. T. Wu, Jinbin Cao
Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field which is difficult to directly measure. Various analytic models and numerical codes exist but their results often drastically differ. Thus a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a non-linear force-free field code (CESE-MHD-NLFFF) and a non-force-free field (NFFF) code in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO/AIA. It is found that the CESE-MHD-NLFFF code with preprocessed magnetogram performs the best, outputting a field which matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ~10 degree. This suggests that the CESE-MHD-NLFFF code, even without using the information of coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential-field give comparable results of mean misalignment angle (~30 degree). Thus further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.
Qingjun Liu, Chaowei Jiang, Xuesheng Feng, Pingbing Zuo, Yi Wang
Jun 24, 2024·astro-ph.SR·PDF Coronal mass ejections from the Sun are not always initiated along a radial trajectory; such non-radial eruptions are well known to be caused by the asymmetry of the pre-eruption magnetic configuration, which is primarily determined by the uneven distribution of magnetic flux at the photosphere. Therefore, it is naturally expected that the non-radial eruptions should be rather common, at least as frequent as radial ones, given the typically asymmetrical nature of photospheric magnetic flux. However, statistical studies have shown that only a small fraction of eruptions display non-radial behavior. Here we aim to shed light on this counterintuitive fact, based on a series of numerical simulations of eruption initiation in bipolar fields with different asymmetric flux distributions. As the asymmetry of the flux distribution increases, the eruption direction tends to deviate further away from the radial path, accompanied by a decrease in eruption intensity. In case of too strong asymmetry, no eruption is triggered, indicating that excessively inclined eruptions cannot occur. Therefore, our simulations suggest that asymmetry plays a negative role in producing eruption, potentially explaining the lesser frequency of non-radial solar eruptions compared to radial ones. With increasing asymmetry, the degree of non-potentiality the field can attain is reduced. Consequently, the intensity of the pre-eruption current sheet decreases, and reconnection becomes less efficient, resulting in weaker eruptions.
Chaowei Jiang, Xueshang Feng
Numerical reconstruction/extrapolation of coronal nonlinear force-free magnetic field (NLFFF) usually takes the photospheric vector magnetogram as input at the bottom boundary. Magnetic field observed at the photosphere, however, contains force which is in conflict with the fundamental assumption of the force-free model and measurement noise which is unfavorable for practical computation. Preprocessing of the raw magnetogram has been proposed by Wiegelmann, Inhester, and Sakurai (2006) to remove the force and noise for providing better input for NLFFF modeling. In this paper we develop a new code of magnetogram preprocessing which is consistent with our extrapolation method CESE-MHD-NLFFF (Jiang, Feng, and Xiang, 2012; Jiang and Feng, 2012). Basing on a magnetic-splitting rule that a magnetic field can be split into a potential field part and a non-potential part, we split the magnetogram and deal with the two parts separately. Preprocessing of the magnetogram's potential part is based on a numerical potential field model, and the non-potential part is preprocessed using the similar optimization method of Wiegelmann et al (2006). The code is applied to the SDO/HMI data and results show that the method can remove efficiently the force and noise and improve the quality of extrapolation.
Wen He, Chaowei Jiang, Peng Zou, Aiying Duan, Xueshang Feng, Pingbing Zuo, Yi Wang
Feb 12, 2020·astro-ph.SR·PDF Solar eruptions are the most powerful drivers of space weather. To understand their cause and nature, it is crucial to know how the coronal magnetic field evolves before eruption. Here we study the formation process of a relatively large-scale magnetic flux rope (MFR) in active region NOAA~12371 that erupts with a major flare and coronal mass ejection on 2015 June 21. A data-driven numerical magnetohydrodynamic model is employed to simulate three-dimensional coronal magnetic field evolution of one-day duration before the eruption. Comparison between the observed features and our modeled magnetic field discloses how the pre-eruption MFR forms. Initially, the magnetic field lines were weakly twisted as being simple sheared arcades. Then a long MFR was formed along the polarity inversion line due to the complex photospheric motion, which is mainly shearing rather than twisting. The presence of the MFR is evidenced by a coherent set of magnetic field lines with twist number above unity. Below the MFR a current sheet is shown in the model, suggesting that tether-cutting reconnection plays a key role in the MFR formation. The MFR's flux grows as more and more field lines are twisted due to continuous injection of magnetic helicity by the photospheric motions. Meanwhile, the height of the MFR's axis increases monotonely from its formation. By an analysis of the decay index of its overlying field, we suggest that it is because the MFR runs into the torus instability regime and becomes unstable that finally triggers the eruption.
Chaowei Jiang, Jun Chen, Aiying Duan, Xinkai Bian, Xinyi Wang, Jiaying Li, Peng Zou, Xueshang Feng
Sep 17, 2021·astro-ph.SR·PDF Magnetic flux ropes (MFRs) constitute the core structure of coronal mass ejections (CMEs), but hot debates remain on whether the MFR forms before or during solar eruptions. Furthermore, how flare reconnection shapes the erupting MFR is still elusive in three dimensions. Here we studied a new MHD simulation of CME initiation by tether-cutting magnetic reconnection in a single magnetic arcade. The simulation follows the whole life, including the birth and subsequent evolution, of an MFR during eruption. In the early phase, the MFR is partially separated from its ambient field by a magnetic quasi-separatrix layer (QSL) that has a double-J shaped footprint on the bottom surface. With the ongoing of the reconnection, the arms of the two J-shaped footprints continually separate from each other, and the hooks of the J shaped footprints expand and eventually become closed almost at the eruption peak time, and thereafter the MFR is fully separated from the un-reconnected field by the QSL. We further studied the evolution of the toroidal flux in the MFR and compared it with that of the reconnected flux. Our simulation reproduced an evolution pattern of increase-to-decrease of the toroidal flux, which is reported recently in observations of variations in flare ribbons and transient coronal dimming. The increase of toroidal flux is owing to the flare reconnection in the early phase that transforms the sheared arcade to twisted field lines, while its decrease is a result of reconnection between field lines in the interior of the MFR in the later phase.
Chaowei Jiang, Xiaoli Yan, Xueshang Feng, Aiying Duan, Qiang Hu, Pingbing Zuo, Yi Wang
As a fundamental magnetic structure in the solar corona, electric current sheets (CSs) can form either prior to or during solar flare, and they are essential for magnetic energy dissipation in the solar corona by enabling magnetic reconnection. However static reconstruction of CS is rare, possibly due to limitation inherent in available coronal field extrapolation codes. Here we present the reconstruction of a large-scale pre-flare CS in solar active region 11967 using an MHD-relaxation model constrained by SDO/HMI vector magnetogram. The CS is found to be associated with a set of peculiar homologous flares that exhibit unique X-shaped ribbons and loops occurring in a quadrupolar magnetic configuration. This is evidenced by that the field lines traced from the CS to the photosphere form an X shape which nearly precisely reproduces the shape of the observed flare ribbons, suggesting that the flare is a product of the dissipation of the CS through reconnection. The CS forms in a hyperbolic flux tube, which is an intersection of two quasi-separatrix layers. The recurrence of the X-shaped flares might be attributed to the repetitive formation and dissipation of the CS, as driven by the photospheric footpoint motions. These results demonstrate the power of data-constrained MHD model in reproducing CS in the corona as well as providing insight into the magnetic mechanism of solar flares.
Chaowei Jiang, Xueshang Feng
Magnetic field in the solar corona is usually extrapolated from photospheric vector magnetogram using a nonlinear force-free field (NLFFF) model. NLFFF extrapolation needs a considerable effort to be devoted for its numerical realization. In this paper we present a new implementation of the magnetohydrodynamics (MHD)-relaxation method for NLFFF extrapolation. The magneto-frictional approach which is introduced for speeding the relaxation of the MHD system is novelly realized by the spacetime conservation-element and solution-element (CESE) scheme. A magnetic field splitting method is used to further improve the computational accuracy. The bottom boundary condition is prescribed by changing the transverse field incrementally to match the magnetogram, and all other artificial boundaries of the computational box are simply fixed. We examine the code by two types of NLFFF benchmark tests, the Low & Lou (1990) semi-analytic force-free solutions and a more realistic solar-like case constructed by van Ballegooijen et al. (2007). The results show that our implementation are successful and versatile for extrapolations of either the relatively simple cases or the rather complex cases which need significant rebuilding of the magnetic topology, e.g., a flux rope. We also compute a suite of metrics to quantitatively analyze the results and demonstrate that the performance of our code in extrapolation accuracy basically reaches the same level of the present best-performing code, e.g., that developed by Wiegelmann (2004).
Chaowei Jiang, Shi Tsan Wu, Vasyl B Yurchyshyn, Haimin Wang, Xueshang Feng, Qiang Hu
Jun 30, 2016·astro-ph.SR·PDF We study the physical mechanism of a major X-class solar flare that occurred in the super NOAA active region (AR) 12192 using a data-driven numerical magnetohydrodynamic (MHD) modeling complemented with observations. With the evolving magnetic fields observed at the solar surface as bottom boundary input, we drive an MHD system to evolve self-consistently in correspondence with the realistic coronal evolution. During a two-day time interval, the modeled coronal field has been slowly stressed by the photospheric field evolution,which gradually created a large-scale coronal current sheet, i.e., a narrow layer with intense current, in the core of the AR. The current layer was successively enhanced until it became so thin that a tether-cutting reconnection between the sheared magnetic arcades was set in, which led to a flare. The modeled reconnecting field lines and their footpoints match well the observed hot flaring loops and the flare ribbons, respectively, suggesting that the model has successfully "reproduced" the macroscopic magnetic process of the flare. In particular, with simulation, we explained why this event is a confined eruption-the consequent of the reconnection is the shared arcade instead of a newly formed flux rope. We also found much weaker magnetic implosion effect comparing to many other X-class flares
Chaowei Jiang, S. T. Wu, Xueshang Feng, Qiang Hu
Aug 20, 2015·astro-ph.SR·PDF Solar active region (AR) 11283 is a very magnetically complex region and it has produced many eruptions. However, there exists a non-eruptive filament in the plage region just next to an eruptive one in the AR, which gives us an opportunity to perform a comparison analysis of these two filaments. The coronal magnetic field extrapolated using a CESE-MHD-NLFFF code (Jiang & Feng 2013) reveals that two magnetic flux ropes (MFRs) exist in the same extrapolation box supporting these two filaments, respectively. Analysis of the magnetic field shows that the eruptive MFR contains a bald-patch separatrix surface (BPSS) co-spatial very well with a pre-eruptive EUV sigmoid, which is consistent with the BPSS model for coronal sigmoids. The magnetic dips of the non-eruptive MFRs match Hα observation of the non-eruptive filament strikingly well, which strongly supports the MFR-dip model for filaments. Compared with the non-eruptive MFR/filament (with a length of about 200 Mm), the eruptive MFR/filament is much smaller (with a length of about 20 Mm), but it contains most of the magnetic free energy in the extrapolation box and holds a much higher free energy density than the non-eruptive one. Both the MFRs are weakly twisted and cannot trigger kink instability. The AR eruptive MFR is unstable because its axis reaches above a critical height for torus instability, at which the overlying closed arcades can no longer confine the MFR stably. On the contrary, the quiescent MFR is very firmly held by its overlying field, as its axis apex is far below the torus-instability threshold height. Overall, this comparison investigation supports that MFR can exist prior to eruption and the ideal MHD instability can trigger MFR eruption.
Jinnan Cai, Ling Zhang, Chaowei Jiang, Kuo Yan, Xueshang Feng, Pingbing Zuo, Yi Wang
Feb 20, 2025·astro-ph.SR·PDF Coronal mass ejections (CMEs) are phenomena in which the Sun suddenly releases a mass of energy and magnetized plasma, potentially leading to adverse space weather. Numerical simulation provides an important avenue for comprehensively understanding the structure and mechanism of CMEs. Here we present a global-corona MHD simulation of a CME originating from sheared magnetic arcade and its interaction with the near-Sun solar wind. Our simulation encompasses the pre-CME phase with gradual accumulation of free magnetic energy (and building up of a current sheet within the sheared arcade) as driven by the photospheric shearing motion, the initiation of CME as magnetic reconnection commences at the current sheet, and its subsequent evolution and propagation to around 0.1 AU. A twisted magnetic flux rope (MFR), as the main body of the CME, is created by the continuous reconnection during the eruption. By interacting with the ambient field, the MFR experiences both rotation and deflection during the evolution. The CME exhibits a typical three-part structure, namely a bright core, a dark cavity and a bright front. The bright core is mainly located at the lower part of the MFR, where plasma is rapidly pumped in by the high-speed reconnection outflow. The dark cavity contains both outer layer of the MFR and its overlying field that expands rapidly as the whole magnetic structure moves out. The bright front is formed due to compression of plasma ahead of the fast-moving magnetic structure. Future data-driven modeling of CME will be built upon this simulation with real observations used for the bottom boundary conditions.
Chaowei Jiang, Aiying Duan, Peng Zou, Zhenjun Zhou, Xinkai Bian, Xueshang Feng, Pingbing Zuo, Yi Wang
Jul 29, 2023·astro-ph.SR·PDF Solar eruptions are explosive disruption of coronal magnetic fields, and often launch coronal mass ejections into the interplanetary space. Intriguingly, many solar eruptions fail to escape from the Sun, and the prevailing theory for such failed eruption is based on ideal MHD instabilities of magnetic flux rope (MFR); that is, a MFR runs into kink instability and erupts but cannot reach the height for torus instability. Here, based on numerical MHD simulation, we present a new model of failed eruption in which magnetic reconnection plays a leading role in the initiation and failure of the eruption. Initially, a core bipolar potential field is embedded in a background bipolar field, and by applying shearing and converging motions to the core field, a current sheet is formed within the core field. Then, tether-cutting reconnection is triggered at the current sheet, first slow for a while and becoming fast, driving an erupting MFR. Eventually, the rise of MFR is halted by the downward magnetic tension force of the overlying field, although the MFR apex has well exceeded the critical height of torus instability. More importantly, during the rise of the MFR, it experiences a significant rotation around the vertical axis (with a direction contrary to that predicted by kink instability), rendering the field direction at the rope apex almost inverse to the overlying field. As a result, a strong current sheet is formed between the MFR and the overlying flux, and reconnection occurring in this current sheet ruins completely the MFR.
Chaowei Jiang, Shin Toriumi
A data-driven active region evolution (DARE) model has been developed to study the complex structures and dynamics of solar coronal magnetic fields. The model is configured with typical coronal environment of tenuous gas governed by strong magnetic field, and thus its lower boundary is set at the base of the corona, but driven by magnetic fields observed in the photosphere. A previous assessment of the model using data from a flux emergence simulation (FES) showed that the DARE failed to reproduce the coronal magnetic field in the FES, which is attributed to the fact that the photospheric data in the FES has a very strong Lorentz force and therefore spurious flows are generated in the DARE model. Here we further test the DARE by using three sets of data from the FES sliced at incremental heights, which correspond to the photosphere, the chromosphere and the base of the corona. It is found that the key difference in the three sets of data is the extent of the Lorentz force, which makes the data-driven model perform very differently. At the two higher levels above the photosphere, the Lorentz force decreases substantially, and the DARE model attains results in much better agreement with the FES, confirming that the Lorentz force in the boundary data is a key issue affecting the results of the DARE model. However, unlike the FES data, the photospheric field from SDO/HMI observations has recently been found to be very close to force-free. Therefore, we suggest that it is still reasonable to use the photospheric magnetic field as approximation of the field at the coronal base to drive the DARE model.
Chaowei Jiang, S. T. Wu, Xueshang Feng, Qiang Hu
Oct 30, 2013·astro-ph.SR·PDF We present a magnetic analysis of the formation and eruption of an active region (AR) sigmoid in AR 11283 from 2011 September 4 to 6. To follow the quasi-static evolution of the coronal magnetic field, we reconstruct a time sequence of static fields using a recently developed nonlinear force-free field model constrained by the SDO/HMI vector magnetograms. A detailed analysis of the fields compared with the SDO/AIA observations suggests the following scenario for the evolution of the region. Initially, a new bipole emerges into the negative polarity of a pre-existing bipolar AR, forming a null point topology between the two flux systems. A weakly twisted flux rope (FR) is then built up slowly in the embedded core region, largely through flux-cancellation photospheric reconnections, forming a bald patch separatrix surface (BPSS) separating the FR from its ambient field. The FR grows gradually until its axis runs into a torus instability (TI) domain near the end of the third day, and the BPSS also develops a fully S-shape. Unlike in the case of standard TI, the FR does not erupt instantly since it is still attached at the photosphere along the bald patch (BP) portion of the polarity inversion line. The combined effects of the TI-driven expansion of the FR and the line-tying at the BP tear the FR into two parts with the upper portion freely expelled and the lower portion remaining behind the post-flare arcades. This process dynamically perturbs the BPSS and results in the transient enhanced brightening of the sigmoid. The accelerated expansion of the upper portion of the FR strongly pushes its envelope flux near the null point and triggers breakout reconnection at the null, as evidenced by a remarkable circular flare ribbon, which further facilitates the eruption. We discuss the important implications of these results for the formation and disruption of sigmoid region with FR.
Qingjun Liu, Chaowei Jiang, Zhipeng Liu
Apr 10, 2025·astro-ph.SR·PDF Before solar eruptions, a short-term slow-rise phase is often observed, during which the pre-eruption structure ascends at speeds much greater than the photospheric motions but much less than those of the eruption phase. Numerical magnetohydrodynamic (MHD) simulations of the coronal evolution driven by photospheric motions up to eruptions have been used to explain the slow-rise phase, but their bottom driving speeds are much larger than realistic photospheric values. Therefore, it remains an open question how the excessively fast bottom driving impacts the slow-rise phase. Here we modelled the slow-rise phase before eruption initiated from a continuously sheared magnetic arcade. In particular, we performed a series of experiments with the bottom driving speed unprecedentedly approaching the photospheric value of around $1$ km s$^{-1}$. The simulations confirmed that the slow-rise phase is an ideal MHD process, i.e., a manifestation of the growing expansion of the sheared arcade in the process of approaching a fully open field state. The overlying field line above the core flux has a slow-rise speed modulated by the driving speed's magnitude but is always over an order of magnitude larger than the driving speed. The core field also expands with speed much higher than the driving speed but much lower than that of the overlying field. By incrementally reducing the bottom-driving speed to realistic photospheric values, we anticipate better matches between the simulated slow-rise speeds and some observed ones.
Zhenjun Zhou, Rui Liu, Xing Cheng, Chaowei Jiang, Yuming Wang, Lijuan Liu, Jun Cui
Feb 12, 2020·astro-ph.SR·PDF The orientation, chirality, and dynamics of solar eruptive filaments is a key to understanding the magnetic field of coronal mass ejections (CMEs) and therefore to predicting the geoeffectiveness of CMEs arriving at Earth. However, confusion and contention remain over the relationship between the filament chirality, magnetic helicity, and sense of rotation during eruption. To resolve the ambiguity in observations, in this paper, we used stereoscopic observations to determine the rotation direction of filament apex and the method proposed by Chen et al. (2014) to determine the filament chirality. Our sample of 12 eruptive active-region filaments establishes a strong one-to-one relationship, i.e., during the eruption, sinistral/dextral filaments (located in the southern/northern hemisphere) rotate clockwise/counterclockwise when viewed from above, and corroborates a weak hemispheric preference, i.e., a filament and related sigmoid both exhibit a forward (reverse) S shape in the southern (northern) hemisphere, which suggests that the sigmoidal filament is associated with a low-lying magnetic flux rope with its axis dipped in the middle. As a result of rotation, the projected S shape of a filament is anticipated to be reversed during eruption.
Zhenjun Zhou, Chaowei Jiang, Rui Liu, Yuming Wang, Lijuan Liu, Jun Cui
Feb 18, 2022·astro-ph.SR·PDF The eruptions of solar filaments often show rotational motion about their rising direction, but it remains elusive what mechanism governs such rotation and how the rotation is related to the initial morphology of the pre-eruptive filament (and co-spatial sigmoid), filament chirality, and magnetic helicity. The conventional view regarding the rotation as a result of a magnetic flux rope (MFR) under-going the ideal kink instability still has confusion in explaining these relationships. Here we proposed an alternative explanation for the rotation during eruptions, by analyzing a magnetohydrodynamic simulation in which magnetic reconnection initiates an eruption from a sheared arcade configuration and an MFR is formed during eruption through the reconnection. The simulation reproduces a reverse S-shaped MFR with dextral chirality, and the axis of this MFR rotates counterclockwise while rising, which compares favorably with a typical filament eruption observed from dual viewing angles. By calculating the twist and writhe numbers of the modeled MFR during its eruption, we found that accompanied with the rotation, the nonlocal writhe of the MFR's axis decreases while the twist of its surrounding field lines increases, and this is distinct from the kink instability, which converts magnetic twist into writhe of the MFR axis.
Chang Liu, Na Deng, Jeongwoo Lee, Thomas Wiegelmann, Chaowei Jiang, Brian R. Dennis, Yang Su, Alina Donea, Haimin Wang
Sep 23, 2014·astro-ph.SR·PDF We carry out a comprehensive investigation comparing the three-dimensional magnetic field restructuring, flare energy release, and the helioseismic response, of two homologous flares, the 2011 September 6 X2.1 (FL1) and September 7 X1.8 (FL2) flares in NOAA AR 11283. In our analysis, (1) a twisted flux rope (FR) collapses onto the surface at a speed of 1.5 km/s after a partial eruption in FL1. The FR then gradually grows to reach a higher altitude and collapses again at 3 km/s after a fuller eruption in FL2. Also, FL2 shows a larger decrease of the flux-weighted centroid separation of opposite magnetic polarities and a greater change of the horizontal field on the surface. These imply a more violent coronal implosion with corresponding more intense surface signatures in FL2. (2) The FR is inclined northward, and together with the ambient fields, it undergoes a southward turning after both events. This agrees with the asymmetric decay of the penumbra observed in the peripheral regions. (3) The amounts of free magnetic energy and nonthermal electron energy released during FL1 are comparable to those of FL2 within the uncertainties of the measurements. (4) No sunquake was detected in FL1; in contrast, FL2 produced two seismic emission sources S1 and S2 both lying in the penumbral regions. Interestingly, S1 and S2 are connected by magnetic loops, and the stronger source S2 has weaker vertical magnetic field. We discuss these results in relation to the implosion process in the low corona and the sunquake generation.
Zhenhua Liu, Chaowei Jiang
Sep 17, 2025·astro-ph.SR·PDF Magnetic field extrapolation from the solar photosphere to the corona plays an important role in solar physics research. In this work, we present a fully-implicit viscous-relaxation nonlinear force-free field (FIVR-NLFFF) extrapolation code based on a viscous magnetohydrodynamic relaxation model. The method solves the magnetic induction equation alongside a simplified momentum equation, which assumes a balance between the Lorentz force and the viscous force. Under this assumption, the velocity field driving the magnetic field evolution is determined instantaneously by the Lorentz force distribution. Through viscous dissipation, the system relaxes toward a minimum-energy state, consistent with the vector magnetogram prescribed at the lower boundary. To enhance numerical stability, we adopt a fully implicit time integration scheme and employ central finite differences for spatial discretization. The resulting system of nonlinear algebraic equations is solved using the Jacobian-free Newton-Krylov method, as implemented in the Portable, Extensible Toolkit for Scientific Computation (PETSc). We validate the code using three benchmark models: the Low and Lou force-free solution, the Titov-Démoulin magnetic flux rope model, and a strongly sheared arcade configuration containing a current sheet. Quantitative comparisons demonstrate good agreement with the reference solutions. Notably, the code's ability to handle discontinuities and reconstruct coronal current sheets makes it a promising tool for studying magnetic fields that may directly trigger solar eruptions.
Yuhu Miao, Yu Liu, A. Elmhamdi, A. S. Kordi, Y. D. Shen, Rehab Al-Shammari, Khaled Al-Mosabeh, Chaowei Jiang, Ding Yuan
Dec 26, 2019·astro-ph.SR·PDF We report a detailed observational study of two quasi-periodic fast-propagating (QFP) magnetosonic wave events occurred on 2011 March 09 and 10, respectively. Interestingly, both the two events have two wave trains (WTs): one main and strong (WT-1) whereas the second appears small and weak (WT-2). Peculiar and common characteristics of the two events are observed, namely: 1) the two QFP waves are accompanied with brightenings during the whole stage of the eruptions; 2) both the two main wave trains are nearly propagating along the same direction; 3) EUV waves are found to be associated with the two events. Investigating various aspects of the target events, we argue that: 1) the second event is accompanied with a flux rope eruption during the whole stage; 2) the second event eruption produces a new filament-like (FL) dark feature; 3) the ripples of the two WT-2 QFP waves seem to result from different triggering mechanisms. Based on the obtained observational results, we propose that the funnel-like coronal loop system is indeed playing an important role in the two WT-1 QFP waves. The development of the second WT-2 QFP wave can be explained as due to the dispersion of the main EUV front. The co-existence of the two events offer thereby a significant opportunity to reveal what driving mechanisms and structures are tightly related to the waves.
Xinyi Wang, Chaowei Jiang, Xueshang Feng, Aiying Duan, Xinkai Bian
Aug 18, 2022·astro-ph.SR·PDF The relationship between solar eruption and sunspot rotation has been widely reported, and the underlying mechanism requires to be studied. Here we performed a full 3D MHD simulation of data-constrained approach to study the mechanism of flare eruptions in active region (AR) NOAA 10930, which is characterized by continuous sunspot rotation and homologous eruptions. We reconstructed the potential magnetic field from the magnetogram of Hinode/SOT as the initial condition and drove the MHD system by applying continuous sunspot rotation at the bottom boundary. The key magnetic structure before the major eruptions and the pre-formed current sheet were derived, which is responsible for the complex MHD evolution with multiple stages. The major eruptions were triggered directly by fast reconnection in the pre-formed current sheet above the main polarity inversion line between the two major magnetic polarities of the AR. Furthermore, our simulation shows the homologous eruption successfully. It has reasonable consistence with observations in relative strength, energy release, X-ray and Hα features and time interval of eruptions. In addition, the rotation angle of the sunspot before the first eruption in the simulation is also close to the observed value. Our simulation offers a scenario different from many previous studies based on ideal instabilities of twisted magnetic flux rope, and shows the importance of sunspot rotation and magnetic reconnection in efficiently producing homologous eruptions by continuous energy injection and impulsive energy release in a recurrent way.