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A magnetic flux rope constructed by the TDm model. The average twist of the flux rope is about 1.83 turns. Selected field lines from this flux rope were used for 1D simulations of filament threads.
Source publication
As one of the main formation mechanisms of solar filament formation, the chromospheric evaporation–coronal condensation model has been confirmed by numerical simulations to explain the formation of filament threads very well in flux tubes with single dips. However, coronal magnetic extrapolations indicated that some magnetic field lines might posse...
Contexts in source publication
Context 1
... two values are small enough to guarantee the model to be in a force-free and divergence-free state. The final magnetic-field distribution is illustrated in Figure 2. The twist of a flux rope and the number of dips are highly correlated, so we also calculate the twist using the formula provided by Berger & Prior (2006). ...
Context 2
... illustrated in Figure 2, the TDm flux-rope core is weakly twisted while the outer shell is highly twisted. This magnetic model includes non-dipped, single-dipped, and multiply-dipped field lines. ...
Context 3
... the flux tubes are independent in our helical cases. For a set of flux tubes extracted from the TDm flux-rope system shown in Figure 2 (red triangles in Figure 13), we find that the average length of the independently trapped threads is about 14.52 Mm, but that of the magnetically connected threads is about 5.89 Mm. Thus, in a statistical sense, the length of each thread is highly correlated with the number of threads along one flux tube. ...
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Citations
... Filament fine structures and oscillations are believed to be intimately related to their supporting magnetic structures . For the former, the length and dynamics of filament threads can indicate the structure of the supporting magnetic dip Zhou et al. 2014;Guo et al. 2021bGuo et al. , 2022; the filament morphology, including aspect ratio, the composition of threads, and the horn and cavity can show the twist degree of a flux rope (Guo et al. 2021a; the filament barbs may indicate the bifurcations of a flux rope due to parasitic polarities in the surrounding environment (Aulanier & Demoulin 1998), and the fibrils in a filament channel can be used to determine the chirality of the filament (Martin 1998). As for the filament oscillation, longitudinal oscillations have been widely applied to derive the curvature radius of local field lines Zhang et al. 2012Zhang et al. , 2013Zhang et al. , 2020Zhou et al. 2017Zhou et al. , 2018Ni et al. 2022), and transverse oscillations can be utilized for the estimate of the magnetic-field strength around the filament Zhou et al. 2018). ...
... In the future, these observational data could also set a stage for examining our previously published results based on numerical simulations. For example, long/short filament threads are prone to be formed in shallow/deep magnetic dips (Zhou et al. 2014;Guo et al. 2021b); the fairly short threads that present decayless oscillations are likely to be hosted in multiple-dipped flux tubes Guo et al. 2021b); short-lived threads forming high-speed flows inside the filament imply that they are likely to be supported by weakly twisted flux tubes, and quasi-stationary threads that generally present the oscillations are more likely to be hosted in highly twisted flux tubes ). In addition, the CHASE spectroscopic observations can also provide full-disk Doppler velocity distribution with the Hα spectra. ...
... In the future, these observational data could also set a stage for examining our previously published results based on numerical simulations. For example, long/short filament threads are prone to be formed in shallow/deep magnetic dips (Zhou et al. 2014;Guo et al. 2021b); the fairly short threads that present decayless oscillations are likely to be hosted in multiple-dipped flux tubes Guo et al. 2021b); short-lived threads forming high-speed flows inside the filament imply that they are likely to be supported by weakly twisted flux tubes, and quasi-stationary threads that generally present the oscillations are more likely to be hosted in highly twisted flux tubes ). In addition, the CHASE spectroscopic observations can also provide full-disk Doppler velocity distribution with the Hα spectra. ...
Solar filaments often exhibit rotation and deflection during eruptions, which would significantly affect the geoeffectiveness of the corresponding coronal mass ejections (CMEs). Therefore, understanding the mechanisms that lead to such rotation and lateral displacement of filaments is a great concern to space weather forecasting. In this paper, we examine an intriguing filament eruption event observed by the Chinese H α Solar Explorer and the Solar Dynamics Observatory. The filament, which eventually evolves into a CME, exhibits significant lateral drifting during its rising. Moreover, the orientation of the CME flux rope axis deviates from that of the pre-eruptive filament observed in the source region. To investigate the physical processes behind these observations, we perform a data-constrained magnetohydrodynamic simulation. Many prominent observational features in the eruption are reproduced by our numerical model, including the morphology of the eruptive filament, eruption path, and flare ribbons. The simulation results reveal that the magnetic reconnection between the flux rope leg and neighboring low-lying sheared arcades may be the primary mechanism responsible for the lateral drifting of the filament material. Such a reconnection geometry leads to flux rope footpoint migration and a reconfiguration of its morphology. As a consequence, the filament material hosted in the flux rope drifts laterally, and the CME flux rope deviates from the pre-eruptive filament. This finding underscores the importance of external magnetic reconnection in influencing the orientation of a flux rope axis during eruption.
... Filament fine structures and oscillations are well believed to be intimately related to their supporting magnetic structures . For the former, the length and dynamics of filament threads can indicate the structure of the supporting magnetic dip Zhou et al. 2014;Guo et al. 2021bGuo et al. , 2022; the filament morphology, including aspect ratio, composition of threads, horn and cavity, can show the twist degree of a flux rope (Guo et al. 2021a; the filament barbs may indicate the bifurcations of a flux rope due to parasitic polarities in the surrounding environment (Aulanier & Demoulin 1998), and the fibrils in a filament channel can be used to determine the chirality of the filament (Martin 1998). As for the filament oscillation, longitudinal oscillations have been widely applied to derive the curvature radius of local field lines Zhang et al. 2012Zhang et al. , 2013Zhang et al. , 2020Zhou et al. 2017Zhou et al. , 2018Ni et al. 2022), and transverse oscillations can be utilized for the estimate of the magnetic field strength around the filament Zhou et al. 2018). ...
... In the future, these observational data could also set a stage for examining our previously published results based on numerical simulations. For example, long/short filament threads are prone to be formed in shallow/deep magnetic dips (Zhou et al. 2014;Guo et al. 2021b); the fairly short threads that present decayless oscillations are likely to be hosted in multiple-dipped flux tubes Guo et al. 2021b); short-lived threads forming high-speed flows inside the filament imply that they are likely to be supported by weakly twisted flux tubes, and quasistationary threads that generally present the oscillations are more likely to be hosted in highly twisted flux tubes . In addition, the CHASE spectroscopic observations can also provide full-disk Doppler velocity distribu-tion with the Hα spectra. ...
... In the future, these observational data could also set a stage for examining our previously published results based on numerical simulations. For example, long/short filament threads are prone to be formed in shallow/deep magnetic dips (Zhou et al. 2014;Guo et al. 2021b); the fairly short threads that present decayless oscillations are likely to be hosted in multiple-dipped flux tubes Guo et al. 2021b); short-lived threads forming high-speed flows inside the filament imply that they are likely to be supported by weakly twisted flux tubes, and quasistationary threads that generally present the oscillations are more likely to be hosted in highly twisted flux tubes . In addition, the CHASE spectroscopic observations can also provide full-disk Doppler velocity distribu-tion with the Hα spectra. ...
Solar filaments often exhibit rotation and deflection during eruptions, which would significantly affect the geoeffectiveness of the corresponding coronal mass ejections (CMEs). Therefore, understanding the mechanisms that lead to such rotation and lateral displacement of filaments is a great concern to space weather forecasting. In this paper, we examine an intriguing filament eruption event observed by the Chinese H{\alpha} Solar Explorer (CHASE) and the Solar Dynamics Observatory (SDO). The filament, which eventually evolves into a CME, exhibits significant lateral drifting during its rising. Moreover, the orientation of the CME flux rope axis deviates from that of the pre-eruptive filament observed in the source region. To investigate the physical processes behind these observations, we perform a data-constrained magnetohydrodynamic (MHD) simulation. Many prominent observational features in the eruption are reproduced by our numerical model, including the morphology of the eruptive filament, eruption path, and flare ribbons. The simulation results reveal that the magnetic reconnection between the flux-rope leg and neighboring low-lying sheared arcades may be the primary mechanism responsible for the lateral drifting of the filament material. Such a reconnection geometry leads to flux-rope footpoint migration and a reconfiguration of its morphology. As a consequence, the filament material hosted in the flux rope drifts laterally, and the CME flux rope deviates from the pre-eruptive filament. This finding underscores the importance of external magnetic reconnection in influencing the orientation of a flux rope axis during eruption.
... However, we do not adopt the filament height directly as the flux-rope height, for two reasons. First, the filament is generally located at the bottom of the flux rope, so that the filament is likely to deviate from the flux-rope axis (Guo et al. 2021b. Second, the angle between SDO and STEREO is relatively small (∼37°), so it is prone to bring large measurement errors. ...
... Finally, we need to insert a filament according to the observation, which can be done by increasing the density by about 50 times the magnitude, but keeping the gas pressure unchanged (Zhou et al. 2018), where the prominence path is measured from observations. Figure 2(d) shows the side view of the 3D magnetic field lines, temperature distributions, and inserting filament; one can see that the cold filament materials almost exclusively reside at the bottom of the flux rope, consistent with the simulated filament formed with thermal instability or the thermal nonequilibrium process (Xia et al. 2014;Guo et al. 2021bGuo et al. , 2022. ...
Solar filament eruptions, flares, and coronal mass ejections (CMEs) are manifestations of drastic releases of energy in the magnetic field, which are related to many eruptive phenomena, from the Earth’s magnetosphere to black hole accretion disks. With the availability of high-resolution magnetograms on the solar surface, observational data-based modeling is a promising way to quantitatively study the underlying physical mechanisms behind observations. By incorporating thermal conduction and radiation losses in the energy equation, we develop a new data-driven radiative magnetohydrodynamic model, which has the capability of capturing the thermodynamic evolution compared to our previous zero- β model. Our numerical results reproduce the major observational characteristics of the X1.0 flare on 2021 October 28 in NOAA active region 12887, including the morphology of the eruption, the kinematics of the flare ribbons, extreme ultraviolet (EUV) radiations, and the two components of the EUV waves predicted by the magnetic stretching model, i.e., a fast-mode shock wave and a slower apparent wave, due to successive stretching of the magnetic field lines. Moreover, some intriguing phenomena are revealed in the simulation. We find that flare ribbons separate initially and ultimately stop at the outer stationary quasi-separatrix layers (QSLs). Such outer QSLs correspond to the border of the filament channel and determine the final positions of flare ribbons, which can be used to predict the size and the lifetime of a flare before it occurs. In addition, the side views of the synthesized EUV and white-light images exhibit typical three-part structures of CMEs, where the bright leading front is roughly cospatial with the nonwave component of the EUV wave, reinforcing the use of the magnetic stretching model for the slow component of EUV waves.
... However, we do not adopt the filament height directly as the flux-rope height, for two reasons. First, the filament is generally located at the bottom of the flux rope so that the filament is likely to deviate from the flux-rope axis (Guo et al. 2021b. Second, the angle between SDO and STEREO is relatively small (∼ 37 • ), so it is prone to bring large measurement errors. ...
... Finally, we need to insert a filament according to the observation, which can be done by increasing the density by about 50 times of magnitude but keeping the gas pressure unchanged (Zhou et al. 2018), where the prominence path is measured from observations. Figure 2d shows the side view of the 3D magnetic field lines, temperature distributions and the inserting filament, one can see that the cold filament materials almost reside in the bottom of the flux rope, consistent with the simulated filament formed with the thermal instability or the thermal non-equilibrium process (Xia et al. 2014;Guo et al. 2021bGuo et al. , 2022. ...
Solar filament eruptions, flares and coronal mass ejections (CMEs) are manifestations of drastic release of energy in the magnetic field, which are related to many eruptive phenomena from the Earth magnetosphere to black hole accretion disks. With the availability of high-resolution magnetograms on the solar surface, observational data-based modelling is a promising way to quantitatively study the underlying physical mechanisms behind observations. By incorporating thermal conduction and radiation losses in the energy equation, we develop a new data-driven radiative magnetohydrodynamic (MHD) model, which has the capability to capture the thermodynamic evolution compared to our previous zero-\b{eta} model. Our numerical results reproduce major observational characteristics of the X1.0 flare on 2021 October 28 in NOAA active region (AR) 12887, including the morphology of the eruption, kinematic of flare ribbons, extreme-ultraviolet (EUV) radiations, and two components of the EUV waves predicted by the magnetic stretching model, i.e., a fast-mode shock wave and a slower apparent wave due to successive stretching of magnetic field lines. Moreover, some intriguing phenomena are revealed in the simulation. We find that flare ribbons separate initially and ultimately stop at the outer stationary quasi-separatrix layers (QSLs). Such outer QSLs correspond to the border of the filament channel and determine the final positions of flare ribbons, which can be used to predict the size and the lifetime of a flare before it occurs. In addition, the side view of the synthesized EUV and white-light images exhibit typical three-part structures of CMEs, where the bright leading front is roughly cospatial with the non-wave component of the EUV wave, reinforcing the magnetic stretching model for the slow component of EUV waves.
... Prominences are cool and dense plasmas suspended in the solar atmosphere (Labrosse et al., 2010;Mackay et al., 2010;Parenti, 2014;Chen, Xu, and Ding, 2020). The materials are formed at magnetic dips due to levitation from below the photosphere (Lites, 2005), direct mass injection , and catastrophic condensation as a result of thermal instability of evaporated hot plasmas from the chromosphere (Xia et al., 2011;Luna, Karpen, and DeVore, 2012;Zhou et al., 2014;Guo et al., 2021). Two types of magnetic configurations are believed to provide upward tension force to balance the gravity of prominences: sheared arcades (Kippenhahn and Schlüter, 1957;Zhang et al., 2015) and twisted flux ropes (Kuperus and Raadu, 1974;Low and Hundhausen, 1995;Shibata et al., 1995;Rust and Kumar, 1996;Guo et al., 2022). ...
In this paper, we report the multiwavelength observations of an erupting prominence and the associated CME on 13 May 2013. The event occurs behind the western limb in the field of view of SDO/AIA. The prominence is supported by a highly twisted magnetic flux rope and shows rapid rotation in the counterclockwise direction during the rising motion. The rotation of the prominence lasts for ~47 minutes. The average period, angular speed, and linear speed are ~806 s, ~0.46 rad/min, and ~355 km/s, respectively. The total twist angle reaches ~7$\pi$, which is considerably larger than the threshold for kink instability. Writhing motion during 17:42-17:46 UT is clearly observed by SWAP in 174 {\AA} and STEREO-B/EUVI in 304 {\AA} after reaching an apparent height of ~405 Mm. Therefore, the prominence eruption is most probably triggered by kink instability. A pair of conjugate flare ribbons and post-flare loops are created and observed by STA/EUVI. The onset time of writhing motion is consistent with the commencement of the impulsive phase of the related flare. The 3D morphology and positions of the associated CME are derived using the graduated cylindrical shell (GCS) modeling. The kinetic evolution of the reconstructed CME is divided into a slow-rise phase and a fast-rise phase by the writhing motion. The edge-on angular width of the CME is a constant (60 degree), while the face-on angular width increases from 96 to 114 degree, indicating a lateral expansion. The latitude of the CME source region decreases slightly from 18 to 13 degree, implying an equatorward deflection during propagation.
... Prominences are cool and dense plasmas suspended in the solar atmosphere (Labrosse et al., 2010;Mackay et al., 2010;Parenti, 2014;Chen, Xu, and Ding, 2020). The materials are formed at magnetic dips due to levitation from below the photosphere (Lites, 2005), direct mass injection , and catastrophic condensation as a result of thermal instability of evaporated hot plasmas from the chromosphere (Xia et al., 2011;Luna, Karpen, and DeVore, 2012;Zhou et al., 2014;Guo et al., 2021). Two types of magnetic configurations are believed to provide upward tension force to balance the gravity of prominences: sheared arcades (Kippenhahn and Schlüter, 1957;Zhang et al., 2015) and twisted flux ropes (Kuperus and Raadu, 1974;Low and Hundhausen, 1995;Shibata et al., 1995;Rust and Kumar, 1996;Guo et al., 2022). ...
In this paper, we report the multiwavelength observations of an erupting prominence and the associated CME on 13 May 2013. The event occurs behind the western limb in the field of view of SDO/AIA. The prominence is supported by a highly twisted magnetic flux rope and shows rapid rotation in the counterclockwise direction during the rising motion. The rotation of the prominence lasts for $\sim$47 minutes. The average period, angular speed, and linear speed are $\sim$806 s, $\sim$0.46 rad min$^{-1}$, and $\sim$355 km s$^{-1}$, respectively. The total twist angle reaches $\sim$7$\pi$, which is considerably larger than the threshold for kink instability. Writhing motion during 17:42$-$17:46 UT is clearly observed by SWAP in 174 {\AA} and EUVI on board the behind STEREO spacecraft in 304 {\AA} after reaching an apparent height of $\sim$405\,Mm. Therefore, the prominence eruption is most probably triggered by kink instability. A pair of conjugate flare ribbons and post-flare loops are created and observed by STA/EUVI. The onset time of writhing motion is consistent with the commencement of the impulsive phase of the related flare. The 3D morphology and positions of the associated CME are derived using the graduated cylindrical shell (GCS) modeling. The kinetic evolution of the reconstructed CME is divided into a slow-rise phase ($\sim$330 km s$^{-1}$) and a fast-rise phase ($\sim$1005 km s$^{-1}$) by the writhing motion. The edge-on angular width of the CME is a constant (60$^{\circ}$), while the face-on angular width increases from 96$^{\circ}$ to 114$^{\circ}$, indicating a lateral expansion. The latitude of the CME source region decreases slightly from $\sim$18$^{\circ}$ to $\sim$13$^{\circ}$, implying an equatorward deflection during propagation.
... In addition, filament-channel models that predict dipped field lines with much larger or smaller radii of curvature than those derived from observed oscillations could be eliminated or severely constrained. For instance, twisted flux-rope models in which most filament plasma resides in dips (concave-upward field lines) far from the axis (e.g., Fan 2018Fan , 2020Guo et al. 2021) could contain relevant field lines with small radii of curvature. Similarly, in models where the filament plasma resides in a cusp-shaped region above a null point (e.g., Litvinenko et al. 2007;Low et al. 2012), the relevant field lines have very small radii of curvature. ...
Understanding the magnetic structure of filament channels is difficult but essential for identifying the mechanism (s) responsible for solar eruptions. In this paper we characterize the magnetic field in a well-observed filament channel with two independent methods, prominence seismology and magnetohydrodynamics flux-rope modeling, and compare the results. In 2014 May and June, active region 12076 exhibited a complex of filaments undergoing repeated oscillations over the course of 12 days. We measure the oscillation periods in the region with both Global Oscillation Network Group H α and Solar Dynamics Observatory (SDO) Advanced Imaging Assembly EUV images, and then utilize the pendulum model of large-amplitude longitudinal oscillations to calculate the radius of curvature of the fields supporting the oscillating plasma from the derived periods. We also employ the regularized Biot–Savart laws formalism to construct a flux-rope model of the field of the central filament in the region based on an SDO Helioseismic and Magnetic Imager magnetogram. We compare the estimated radius of curvature, location, and angle of the magnetic field in the plane of the sky derived from the observed oscillations with the corresponding magnetic-field properties extracted from the flux-rope model. We find that the two models are broadly consistent, but detailed comparisons of the model and specific oscillations often differ. Model observation comparisons such as these are important for advancing our understanding of the structure of filament channels.
Context. Many prominences are supported by magnetic flux ropes. One important question is how we can determine whether the flux rope is weakly twisted or highly twisted.
Aims. In this paper, we attempt to decipher whether prominences supported by weakly twisted and highly twisted flux ropes can manifest different features so that we might distinguish the two types of magnetic structures based on their appearance.
Methods. We performed pseudo three-dimensional simulations of two magnetic flux ropes with different twists.
Results. We find that the resulting two prominences differ in many aspects. The prominence supported by a weakly twisted flux rope is composed mainly of transient threads (∼82.8%), forming high-speed flows inside the prominence, and its horns are evident. Conversely, the prominence supported by a highly twisted flux rope consists mainly of stable quasi-stationary threads (∼60.6%), including longer independently trapped threads and shorter magnetically connected threads. Our simulations also reveal that the prominence spine deviates from the flux rope axis in the vertical direction and from the photospheric polarity inversion line projected on the solar surface, especially for the weakly twisted magnetic flux rope.
Conclusions. The two types of prominences differ significantly in appearance. Our results also suggest that a piling-up of short threads in highly twisted flux ropes might account for the vertical-like threads in some prominences.
Context. A filament channel (FC), a plasma volume where the magnetic field is primarily aligned with the polarity inversion line, is believed to be the pre-eruptive configuration of coronal mass ejections. Nevertheless, evidence for how the FC is formed is still elusive.
Aims. In this paper, we present a detailed study of the build-up of a FC in order to understand its formation mechanism.
Methods. The New Vacuum Solar Telescope (NVST) of the Yunnan Observatory and the Optical and Near-infrared Solar Eruption Tracer (ONSET) of Nanjing University, as well as the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), are used to study the growth process of the FC. Furthermore, we reconstruct the nonlinear force-free field (NLFFF) of the active region using the regularized Biot-Savart laws (RBSL) and the magnetofrictional method to reveal the three-dimensional (3D) magnetic field properties of the FC.
Results. We find that partial filament materials are quickly transferred to longer magnetic field lines formed by small-scale magnetic reconnection, as evidenced by dot-like H α and extreme ultraviolet (EUV) brightenings and subsequent bidirectional outflow jets, as well as untwisting motions. The H α and EUV bursts appear repeatedly at the same location and are closely associated with flux cancelation, which occurs between two small-scale opposite polarities and is driven by shearing and converging motions. The 3D NLFFF model reveals that the reconnection takes place in a hyperbolic flux tube that is located above the flux-cancelation site and below the FC.
Conclusions. The FC is gradually built up toward a twisted flux rope via a series of small-scale reconnection events that occur intermittently prior to the eruption.
In this paper, we present a multi-wavelength analysis to mass-draining and oscillations in a large quiescent filament prior to its successful eruption on 2015 April 28. The eruption of a smaller filament that was parallel and in close, ∼350 proximity was observed to induce longitudinal oscillations and enhance mass-draining within the filament of interest. The longitudinal oscillation with an amplitude of ∼25 Mm and ∼23 km s −1 underwent no damping during its observable cycle. Subsequently the slightly enhanced draining may have excited a eruption behind the limb, leading to a feedback that further enhanced the draining and induced simultaneous oscillations within the filament of interest. We find significant damping for these simultaneous oscillations, where the transverse oscillations proceeded with the amplitudes of ∼15 Mm and ∼14 km s −1 , while the longitudinal oscillations involved a larger displacement and velocity amplitude (∼57 Mm, ∼43 km s −1). The second grouping of oscillations lasted for ∼2 cycles and had the similar period of ∼2 hours. From this, the curvature radius and transverse magnetic field strength of the magnetic dips supporting the filaments can be estimated to be ∼355 Mm and ≥34 G. The mass-draining within the filament of interest lasted for ∼14 hours. The apparent velocity grew from ∼35 km s −1 to ∼85 km s −1 , with the transition being coincident with the occurrence of the oscillations. We conclude that two filament eruptions are sympathetic, i.e. the eruption of the quiescent filament was triggered by the eruption of the nearby smaller filament.
