Sympathetic eruptions of two filaments with an identifiable causal link observed by the Solar Dynamics Observatory
aa r X i v : . [ a s t r o - ph . S R ] F e b Sympathetic eruptions of two filaments with an identifiable causallink observed by the Solar Dynamics Observatory
Zhiping Song , , Yijun Hou , , Jun Zhang , , and Peng Wang ABSTRACT
Filament eruptions occurring at different places within a relatively short timeinternal, but with a certain physical causal connection are usually known as sym-pathetic eruption.
Studies on sympathetic eruptions are not uncommon.However, in the existed reports, the causal links between sympatheticeruptions remain rather speculative.
In this work, we present detailed obser-vations of a sympathetic filament eruption event, where an identifiable causallink between two eruptive filaments is observed. On 2015 November 15, twofilaments (F1 in the north and F2 in the south) were located at the south-western quadrant of solar disk. The main axes of them were almost parallel toeach other. Around 22:20 UT, F1 began to erupt, forming two flare ribbons. Thesouthwestern ribbon apparently moved to southwest and intruded southeastpart of F2. This continuous intrusion caused F2’s eventual eruption. Accompa-nying the eruption of F2, flare ribbons and post-flare loops appeared in northwestregion of F2. Meanwhile, neither flare ribbons nor post-flare loops could be ob-served in southeastern area of F2.
In addition, the nonlinear force-free field(NLFFF) extrapolations show that the magnetic fields above F2 in thesoutheast region are much weaker than that in the northwest region.
These results imply that the overlying magnetic fields of F2 were not uniform. Sowe propose that the southwest ribbon formed by eruptive F1 invaded
F2 fromits southeast region with relatively weaker overlying magnetic fields incomparison with its northwest region, disturbing F2 and leading F2 toerupt eventually.
Subject headings:
Sun: activity — Sun: atmosphere — Sun: filaments, promi-nences — Sun: magnetic fields School of Physics and Materials Science, Anhui University, Hefei 230601, China; [email protected] CAS Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sci-ences, Beijing 100101, China; [email protected] University of Chinese Academy of Sciences, Beijing 100049, China
1. Introduction
Solar filaments are cool and dense plasma suspended in the corona, which are also knownas prominences when observed at the limb of the Sun. It is widely accepted that filamentsare always located above the magnetic polarity inversion lines (PILs). According to theirlocations, the filaments could be divided into three classes: active region filaments forminginside active regions, intermediate filaments arising between active regions, and quiescentfilaments which are located at solar quiescent regions (Zirker et al. 1997; Martin 1998;Mackay et al. 2010). Filament eruptions, solar flares, and coronal mass ejections are oftenseen as different manifestations of the same physical processes, and filament eruptions arebelieved to play a key role in the onset of these eruptions (Schmieder et al. 2013; Filippov2018; Sinha et al. 2019). The popular filament eruption model is that a lifting filamentstretches its overlying magnetic field lines, creating a current sheet between the anti-parallelfield lines, where magnetic reconnection occurs, and then a bulk of plasma and magneticstructure are ejected into the interplanetary space. During a filament eruption, the footprintsof the reconnecting overlying magnetic field lines continuously brighten different regionsin the chromosphere and are observed as two flare ribbons which spread to both sides ofthe filament in a way of apparent motion , while the post-flare loops just are the newlyformed low-lying loop lines (Kopp, & Pneuman 1976;
Miklenic et al. 2007;
Shibata, &Magara 2011; Hou et al. 2016; Yang & Zhang 2018).The eruptions of stable filaments are triggered by the loss of the balance of forces actingon them (Porfir’eva & Yakunina 2013; Kliem et al. 2014; Zaitsev & Stepanov 2018). Severaldifferent mechanisms have been proposed and studied for the initiation of filament eruption,such as flux emergence and cancellation (Zhang et al. 2001; Zheng et al. 2017; Dacie etal. 2018), tether cutting reconnection (Moore et al. 2001; Cheng & Ding 2016; Woods etal. 2018), breakout reconnection (Sterling et al. 2011; Kliem et al. 2013; Sun et al. 2015;Chen et al. 2016), and torus or kink magnetohydrodynamic (MHD) instability (Aulanier etal. 2010; Riley et al. 2011; Hassanin & Kliem 2016; Dechev et al. 2018; Hou et al. 2018;Duchlev et al. 2019). A stable filament can also erupt due to the direct interaction froma surrounding filament, during which the magnetic system of the original stable filamentis disturbed by magnetic reconnections. Results from Yang et al. (2017) showed that twonearby filaments, which were almost perpendicular to each other, could gradually approachto each other and eventually erupt due to the direct collision between them. Furthermore,a filament could also erupt for the mass injection from a surrounding erupting filament (Suet al. 2007).In addition to the filament eruptions mentioned above, sympathetic eruptions betweenfilaments are also ubiquitous. These eruptions are defined as consecutive filament eruptions 3 –occurring within a short time in different locations but having a certain physical connection(T¨or¨ok et al. 2011; Jiang et al. 2014; Yang et al. 2012; Wang et al. 2016; Joshi et al. 2016; Liet al. 2017). Two filaments, which reside above different PILs and share the same overlyingmagnetic system, could interact sympathetically, i.e., the first erupting filament disturbs themagnetic system of the second filament and leads to its eruption (Shen et al. 2012). Aseries of erupting filaments could be connected by magnetic separatrices or quasi-separatrixlayers. These filaments could be disturbed by each other and erupted sympathetically by achain of magnetic reconnections (Schrijver & Title 2011). However, due to the lack of directobservational evidences, it has been debated whether the close temporal correlation betweensympathetic eruptions is purely coincidental, or causally linked. The exact mechanism ofsympathetic eruptions is still not well understood (Biesecker & Thompson 2000; T¨or¨ok etal. 2011; Wang et al. 2018).In the present work, we show a detailed process of sympathetic eruptions of two filamentsby using high-quality data from the Solar Dynamics Observatory (SDO; Pesnell et al. 2012).In this event, a flare ribbon caused by an eruptive filament intruded the location of anadjacent filament and finally led it to erupt. The remainder of this paper is organized asfollows. Section 2 describes the observations and data analysis taken in our study. In Section3, we investigate the sympathetic event and present the results of observation in detail, whichare followed by summary and discussion in Section 4.
2. Observations and Data Analysis
We study sympathetic eruptions of two filaments in the southwest quadrant of solardisk on 2015 November 15-16. The north filament (F1) lies in southwest of AR 12452and the south filament (F2) is located at southeast of AR 12449 and AR 12450. Theyare mainly observed by SDO/Atmospheric Imaging Assembly (AIA; Lemen et al. 2012)and SDO/Helioseismic and Magnetic Imager (HMI; Schou et al. 2012). The AIA providesfull-disk images taken in 10 extreme ultraviolet (EUV) and ultraviolet (UV) wavelengths.The pixel size and cadence of the EUV images are 0. ′′ ′′ The HMI and AIA images arepreprocessed by standard routines in solar software package (SSW), and all thedata are differentially rotated to a reference time (00:00 UT on November 16). α observations from the Global Oscillation Network Group (GONG; Harveyet al. 2011). GONG has collected H α images observed at seven sites around the world sincemid-2010 and provides successive global H α observations online. In order to reconstruct the three-dimensional (3D) magnetic fields above F1and F2, we perform nonlinear force-free field (NLFFF) extrapolation by using theoptimization method (Wheatland et al. 2000; Wiegelmann 2004). The boundarycondition for the NLFFF extrapolation is an HMI full-disk vector magnetogramwith a pixel spacing of 0. ′′ ◦ ambiguity(Metcalf 1994; Leka et al. 2009). Then we transform the vector magnetic fieldand the geometric mapping of the observed field in the image plane into theheliographic plane (Gary & Hagyard 1990). The NLFFF calculation is conductedwithin a box of × × uniformly spaced grid points with dx = dy = dz = 1 . ′′ .Moreover, we calculate the decay index n of the horizontal magnetic fields aboveF2, which is defined as n ( z ) = − zdln ( Bh ) /dz (Kliem & T¨or¨ok 2006) and providesimportant information about the strapping fields stabilizing the filament.3. Results The event analyzed here occurred on 2015 November 15-16. As shown in Figure 1, two sinistral filaments (F1 in the north and F2 in the south) were located at the southwestquadrant of solar disk. The filament F1 lay in the southwest of AR 12452 and the filamentF2 was near southeast of AR 12449 and AR12450 on November 15.
In H α observations,the lengths of them are about 500 Mm and 250 Mm, respectively. Two filamentsboth lay above the PILs and their main axes were almost parallel to each other. The filamentF1 and filament F2 were separated by negative magnetic fields between them.Since about 22:20 UT on November 15, the northern filament (F1) began to rise quicklyand then erupted. After examining magnetograms and 193 ˚A images, we notice that magneticflux cancellation occurred around barbs of F1 accompanied by 193 ˚A brightening before F1eruption (see Figure 2 and online animation of this figure). The FOVs of panels (c1)-(c3)and panels (d1)-(d3) in Figure 2 are outlined by the blue rectangles in panels (a) and (b),respectively. And four sites of flux cancellation along the PIL of F1 are marked by thegreen boxes where the magnetic fields with opposite polarities kept approaching to each 5 –other (see panel (b)). In these four box regions, the magnetograms are replaced by thecorresponding HMI magnetograms on November 15 around 20:26 UT, 21:20 UT, 21:56 UT,and 20:35 UT, respectively. To investigate the temporal evolution of the flux cancellationand brightening in detail, we focus on the box region “2”. Combining the AIA 193 ˚A imagesand HMI magnetograms, one can see that the flux cancellation is accompanied by the EUVbrightening. From 17:00 UT to 22:15 UT, the emission enhancement (see panels (c1)-(c3)) aswell as the flux cancellation (see panels (d1)-(d3)) continuously appeared in this box region.Along the red line “A-B” shown in panel (d2), we make a time-slice plot (see panel (e)) inHMI LOS magnetograms. Moreover, the 193 ˚A light curve of the area contoured by thegreen curve in panel (c3) is superimposed on the time-slice plot (see the green curve in panel(e)). It is shown that two magnetic fields with opposite polarities kept approaching to eachother in the box region “2” from 20:00 UT to 24:00 UT. Meanwhile, the emission strengthmentioned above continued to enhance from 21:00 UT to 22:20 UT and reached a peak atabout 22:20 UT (see the red dotted line in panel (e)).The detailed process of F1 eruption is displayed in Figure 3. We focus on the northwestarea of F1 (see the FOV marked by the green square in panel (a1)), where eruption of F1 isthe most significant, to show the F1 eruption in detail. Since about 22:20 UT, F1 started torise and then erupted northwestward at about 23:00 UT, accompanied by formations of twoflare ribbons (outlined by the green dotted curves in panel (a3)).
These two flare ribbonsappeared on both sides of the magnetic neutral line of F1 and then apparentlyseparated from each other in directions perpendicular to the magnetic neutralline of F1.
The northeastern ribbon spread northeastward and the southwestern one spreadsouthwestward. To study the kinematic evolution of F1, we made time slices from 304 ˚A, 171˚A, and 131 ˚A images along the cut “C-D” shown in panel (a2). As displayed by the time-slice plots in panels (b1)-(b3), the filament F1 underwent three kinematic phases: slowrising, accelerating and constant velocity.
By linear fitting, the erupting speeds of F1during constant velocity phase are estimated as about 100 km s − . The light curve of 193˚A in the area contoured by the green curve in Figure 2(c3) is superimposed on the time-sliceimage of 304 ˚A (see the green curve in panel (b1)). It can be seen that the peak time ofbrightening and eruptive time of F1 was almost coincident (see the vertical white dotted linein panel (b1)). The detailed process of F1 eruption is also seen in online animation of Figure3. Once formation, the southwestern flare ribbon related to eruptive F1 (FRF1) continuously apparently moved to southwest. At about 23:50 UT, the northwesternpart of FRF1 ceased its motion, but the southeastern part of FRF1 kept movingsouthwestward, approaching the site of F2 and intruded the location of F2 around00:18 UT on November 16 (see Figure 4(a1)-(b1)). This intrusion lasted for about 100 6 –minutes. After that, the filament F2 began to lift slowly, and accelerated to erupt eventually(see panels (b2)-(b3)). In order to investigate the kinematic evolution of F2 in detail, wemade time slices (see panels (c1)-(c3)) from 304 ˚A, 171 ˚A and, 131 ˚A images along a slit“E-F” (see panel (b2)). In panels (c1)-(c3), the dashed curves approximate the tracks ofF2 in different wavelengths, the two vertical green dashed lines indicate the times when F2began to rise (t1) and to erupt (t2) respectively. We notice that F2 appeared as dark beltsand it was almost stable before 00:20 UT, when FRF1 reached the site of F2 (panel (b1), seealso the green vertical dashed line “t1” in panels (c1)-(c3)). During 00:20 UT to 01:50 UT,F2 rose slowly accompanied the successive intrusion of FRF1 and the rising speed was about3 km s − . At about 01:50 UT, F2 began to rise quickly and then erupted (see the greenvertical dashed line “t2” in panels (c1)-(c3)), with the speeds of around 120 km s − . Thetemporal evolution of FRF1 spreading, interaction between FRF1 and F2, and F2 eruptionis also shown in online animation of Figure 4.Since about 02:10 UT, the eruptive F2 also produced two flare ribbons at its northwestarea (see the white solid squares in Figure 5), which appeared on both sides of themagnetic neutral line of F2 and then apparently separated from each other indirections perpendicular to the magnetic neutral line of F2 (see panels (a1)-(a3)).The northern ribbon (FRF2) related to F2 eruption approached FRF1 formed by F1 eruption.Finally, there displayed a clear separating line between the two approaching ribbons (panel(a3)), implying that there is a magnetic separatrice between the two filaments and thatF1 and F2 belong to two different magnetic systems. Seen from 171 ˚A, 131 ˚A, and 211 ˚Aimages, two sets of post-flare loops appeared in the northwest area in gradual phases afterthe eruptions of F1 and F2. The footpoints of post-flare loops could be identified as the flareribbons related to the eruptions of F1 and F2, respectively. There are two evidences thatcan be seen about the correlation between the flare ribbons (post-flare loops) andtheir corresponding eruptive filaments. The first one is temporal correlation, i.e.,FRF1 appeared shortly after the F1 eruption (see Figure 3), and FRF2 appearedfollowing immediately the eruptive F2 (see Figure 4). The other one is spatialcorrelation, i.e., the flare ribbons (post-flare loops) formed by different eruptivefilaments appeared on both sides of different magnetic neutral lines (see Figure5).
These post-flare loops and their footpoints are displayed in panels (b1)-(b3). It is shownthat these loops were rooted on the positive and negative magnetic fields on each side ofthe two neutral lines. However, we also notice that neither clear flare ribbons nor obviouspost-flare loops appeared in southeast region of F2 (see the dash-dotted squares in Figure5). The distribution of flare ribbons and post-flare loops related to eruptive F2 impliesthat the overlying magnetic fields of F2 are not uniform, and they are weaker in southeastarea but stronger in northwest region. The temporal evolution of FRF2 and post-flare loops 7 –after F2 eruption is also shown in online animation of Figure 5.
In order to confirm the non-uniformity of the magnetic fields above F2, Weperformed NLFFF reconstruction of the overlying magnetic fields of F2 basedon the photospheric vector magnetic fields at 22:00 UT on 2015 November 15.Moreover, we calculated the decay index distribution of the reconstructed hor-izontal magnetic fields above F2. As shown in Figure 6(a), the red-blue curvedenotes the magnetic neutral line related to F2, and the blue and red segmentscorrespond to the southeast and northwest regions of F2, respectively. It isobvious that the magnetic fields above F2 in the southeast region are weakerthan those in the northwest region (see the green curves). The results shownin panels (b) and (c) also reveal that the decay index of horizontal magneticfields above F2 in the southeast region is significantly larger than that in thenorthwest region. This means that the overlying horizontal magnetic fields ofF2 decay faster with increasing altitude in southeast region than in northwestregion. The NLFFF modeling results shown here well support the observationsand our speculation that the overlying magnetic fields of F2 are not uniform.4. Summary and Discussion
Using the high-quality data from the SDO, we present eruptive processes of two filaments(F1 and F2) that occurred on 2015 November 15-16. F1 and F2 were separated by negativemagnetic fields and their main axes were almost parallel to each other. On November15, a sequence of emergence and cancellation of the magnetic flux appeared inside the F1channel and then F1 erupted. The erupting F1 produced two flare ribbons. The southwesternribbon spread southwestward and intruded the southeastern region of F2, which lasted about100 minutes, and then F2 erupted. The eruptive F2 produced also two flare ribbons inits northwestern region, which moved northward and southward respectively. During theevolution of these ribbons, there displayed a clear separating line between the two nearbyribbons related to F1 and F2 eruptions, implying that there is a magnetic separatrice betweenthe two filaments and that F1 and F2 belong to different magnetic systems. In gradual phasesafter the eruptions of F2, post-flare loops appeared in northwest region of F2, but neitherflare ribbons nor post-flare loops were observed in southeast area of F2.
Furthermore,the NLFFF extrapolated 3D magnetic fields and decay index distribution of thehorizontal fields above F2 reveal that the overlying magnetic fields of F2 in thesoutheast region are weaker than those in the northwest region and that theoverlying horizontal magnetic fields of F2 decay faster with increasing altitude in southeast region than in northwest region.
The eruptions of filaments are closely connected to the evolution of underneath magneticfields, such as magnetic flux emergence and cancellation. The relationship between them hasbeen analyzed in previous studies (Mandrini et al. 2014; Panesar et al. 2016; Zheng et al.2017; Yang, & Chen 2019). Zhang et al. (2001) discovered that when the major solar eruptionevent (a giant filament eruption, a great flare, or an extended Earth-directed coronal massejection) happened, the only obvious magnetic change in the course of the event is magneticflux cancellation at many sites in the vicinity of the filament. Li et al. (2015) found that thelocation of emerging flux within the filament channel is probably crucial to filament eruption.They suggested that if the flux emergence appeared nearby filament’s barbs, flux cancellationwas prone to occur, which probably caused the filament eruption. In the present work, priorto the eruption of F1, obvious magnetic flux cancellation and emission brightening could beobserved in F1 channel (Figure 2). When the emission reached the peak, F1 began to erupt(see the dotted vertical white line in Figure 3(b1)). So, we suggest that the flux cancellationhappening in F1 channel results in F1 eruption.As mentioned above, a filament probably erupts due to the magnetic flux emergenceand cancellation. If there is another stable filament located just beside this erupting filamentcoincidentally, the interaction between these two filaments usually is inevitable and the di-rect collision would result in the eruption of the second filament (Bone et al. 2009; Zhenget al. 2017). However, different from the filament-filament interactions, the sympatheticfilament eruptions occur without direct touching between the bodies of filaments or materialof filaments (Bumba & Klvana 1993; Wang et al. 2001; Lugaz et al. 2017). The exact natureof sympathetic eruptions is still a controversial issue. Observational investigations (Jiang etal. 2011; Shen et al. 2012; Joshi et al. 2016; Wang et al. 2018) and numerical simulations(Ding et al. 2006; T¨or¨ok et al. 2011; Lynch & Edmondson 2013) suggest that magnetic re-connections of large-scale magnetic fields, which are induced indirectly or directly by distantor nearby eruptions, may be the crucial physical links between sympathetic eruptions, forthe reconnections could weaken and partially remove the overlying magnetic fields on theother filaments, resulting in their destabilization and eruptions.In this work, F2 began to erupt about 100 minutes after FRF1 intruded southeast loca-tion of F2 (see Figures 4(b1)-(b3)). And then, we observed two different manifestations innorthwest and southeast regions of F2. There were clear flare ribbons formed by the eruptiveF2 in the northwest area of F2, which spread northward and southward respectively and thenorthern one extended to the edge of FRF1 (see Figure 5(a3)). Meanwhile, clear post-flareloops were also observed in the northwest region of F2. But, neither clear flare ribbons norobvious post-flare loops could be observed in the southeast area of F2 (see Figure 5, and 9 –the online animation of Figure 5). These observational results imply that the distributionof the overlying magnetic fields of F2 is not uniform, i.e., the overlying magnetic fields ofF2 are stronger in its northwest area, but weaker in its southeast region.
The NLFFFreconstructions well support the observations and our speculation that the over-lying magnetic fields of F2 are not uniform (see Figure 6). As shown in Figure 4and its corresponding movie, the northwestern part of FRF1 ceased its apparentmotion to the southwest at about 23:50 UT on November 15, meanwhile thesouthwestern part of FRF1 kept moving southwestward, approaching the siteof F2. We suggest that it is possible that the stronger overlying magnetic fields ofF2 in northwest area partially blocked FRF1 from expanding southwestward further.
Incontrast, the weaker overlying magnetic fields in the southeast region of F2 made F2 to bemore sensitive to external disturbances happening in that region. As a result, when thesoutheast part of FRF1 continuously intruded the southeast site of F2, F2 wasdisturbed to slowly rise and erupt eventually. Note that the AIA observations offull eruption of F2 shows that no active eruption is clearly observed in the south-east part of F2 at the initial phase. The possible reasons, in our opinions, are asfollows: Firstly, the speed at which F2 started to rise is too small to distinguishclearly. Secondly, as shown in the H α observations, the plasma density of F2 inthe southeast region is much less than that in the northwest region (see Figure1(a)). So it is reasonable that the eruption of F2 appeared more obviously inthe northwest region even though it started in the southeast region. Finally,the projection effect may also make a difference here, causing the observationsdifferent from the real situations. Because no any direct touch between F1 and F2 was observed, we conjecture that theinteraction occurring between F1 and F2 belongs to sympathetic one. And the causal link ofthe sympathetic interaction is that FRF1 invades the southeastern region of F2, where theoverflying magnetic fields of F2 are very weak. Based on the multi-wavelength observations,we present a schematic diagram in
Figure 7 to illustrate this sympathetic eruptions event.Difference of field line density in
Figure 7 is used to indicate the non-uniformity distributionof the overlying magnetic fields of F2. Panel (a) represents the initial magnetic topologyof the two filaments and the overlying ambient coronal fields. Flux cancellation happeningaround the barbs of F1 disturbs F1 (see Figure 2) and results in its final eruption (see Figure3). Then two flare ribbons are formed after the eruption of F1, one of which keeps spreadingtoward F2, intruding and disturbing the magnetic system of F2 in its southeast area (panel(b)). As the overlying magnetic fields of F2 are very weak in the disturbed location, thesuccessive disturbance destabilizes F2, and F2 erupts eventually (panel (c), also see Figure4). After the eruptions of F2, the clear flare ribbons (shown by the thick purple curves) and 10 –post-flare loops (shown by the thick red curves in panel (d)) only appear in F2’s northwestregion, where the overlying magnetic fields are strong (panels (c)-(d), also see solid squaresin Figure 5). And the thin purple and red curves in panels (c)-(d), respectively, are employedto indicate the ambiguous flare ribbons and post-flare loops in F2’s southeast area, wherethe overlying magnetic fields are very weak (also see the dash-dotted squares in Figure 5).
In the existing research reports on sympathetic filament eruptions, the di-rectly observable criterion is mostly the correlation of the eruptive time betweentwo filaments . Joshi et al. (2016) interpreted two successive eruptions as sympatheticeruptions, which occurred in different active regions and associated by a chain of magneticreconnections. The phenomenon that fast rise of the second filament began soon after thefirst filament eruption was suggested as sympathetic eruptions (Li et al. 2017). In thepresent work, in addition to the temporal correlation, an identifiable causal link betweentwo sympathetic eruptive filaments was observed. To our knowledge, similar observationshave never been reported before.SDO is a mission of NASA’s Living With a Star (LWS) Program. AIA and HMI dataare courtesy of the NASA/SDO science teams. This work is supported by the NationalNatural Science Foundations of China (U1531113, 11903050, 11533008, 11790304, 11773039,11673035, 11673034, 11873059 and 11790300), the open topic of the Key Laboratory of SolarActivities of the Chinese Academy of Sciences (KLSA201902), the NAOC Nebula TalentsProgram, and Key Programs of the Chinese Academy of Sciences (QYZDJ-SSW-SLH050).
REFERENCES
Aulanier, G., T¨or¨ok, T., D´emoulin, P., & DeLuca, E. E. 2010, ApJ, 708, 314Biesecker, D. A., & Thompson, B. J. 2000, Journal of Atmospheric and Solar-TerrestrialPhysics, 62, 1449Bone, L. A., van Driel-Gesztelyi, L., Culhane, J. L., et al. 2009, Sol. Phys., 259, 31
Borrero, J. M., Tomczyk, S., Kubo, M., et al. 2011, Sol. Phys., 273, 267
Bumba, V., & Klvana, M. 1993, Ap&SS, 199, 45Chen, Y., Du, G., Zhao, D., et al. 2016, ApJ, 820, L37Cheng, X., & Ding, M. D. 2016, ApJS, 225, 16 11 –Dacie, S., T¨or¨ok, T., D´emoulin, P., et al. 2018, ApJ, 862, 117Dechev, M., Koleva, K., & Duchlev, P. 2018, New A, 59, 45Ding, J. Y., Hu, Y. Q., & Wang, J. X. 2006, Sol. Phys., 235, 223Duchlev, P., Dechev, M., & Koleva, K. 2019, Bulgarian Astronomical Journal, 30, 99Filippov, B. 2018, MNRAS, 475, 1646
Gary, G. A., & Hagyard, M. J. 1990, Sol. Phys., 126, 21
Harvey, J. W., Bolding, J., Clark, R., et al. 2011, AAS/Solar Physics Division Abstracts
Kliem, B., & T¨or¨ok, T. 2006, Phys. Rev. Lett., 96, 255002
Kopp, R. A., & Pneuman, G. W. 1976, Sol. Phys., 50, 85
Leka, K. D., Barnes, G., Crouch, A. D., et al. 2009, Sol. Phys., 260, 83
Lemen, J. R., Title, A. M., Akin, D. J., et al. 2012, Sol. Phys., 275, 17Li, S., Su, Y., Zhou, T., et al. 2017, ApJ, 844, 70Li, T., Zhang, J., & Ji, H. 2015, Sol. Phys., 290, 1687Lugaz, N., Temmer, M., Wang, Y., & Farrugia, C. J. 2017, Sol. Phys., 292, 64Lynch, B. J., & Edmondson, J. K. 2013, ApJ, 764, 87 12 –Mackay, D. H., Karpen, J. T., Ballester, J. L., Schmieder, B., & Aulanier, G. 2010,Space Sci. Rev., 151, 333Mandrini, C. H., Schmieder, B., D´emoulin, P., Guo, Y., & Cristiani, G. D. 2014, Sol. Phys.,289, 2041Martin, S. F. 1998, Sol. Phys., 182, 107
Metcalf, T. R. 1994, Sol. Phys., 155, 235
Miklenic, C. H., Veronig, A. M., Vrˇsnak, B., et al. 2007, A&A, 461, 697Moore, R. L., Sterling, A. C., Hudson, H. S., & Lemen, J. R. 2001, ApJ, 552, 833Panesar, N. K., Sterling, A. C., Moore, R. L., & Chakrapani, P. 2016, ApJ, 832, L7Pesnell, W. D., Thompson, B. J., & Chamberlin, P. C. 2012, Sol. Phys., 275, 3Porfir’eva, G. A., & Yakunina, G. V. 2013, Geomagnetism and Aeronomy, 53, 977Riley, P., Lionello, R., Linker, J. A., et al. 2011, Sol. Phys., 274, 361Schmieder, B., D´emoulin, P., & Aulanier, G. 2013, Advances in Space Research, 51, 1967Schou, J., Scherrer, P. H., Bush, R. I., et al. 2012, Sol. Phys., 275, 229Schrijver, C. J., & Title, A. M. 2011, Journal of Geophysical Research (Space Physics), 116,A04108Shen, Y., Liu, Y., & Su, J. 2012, ApJ, 750, 12Shibata, K., & Magara, T. 2011, Living Reviews in Solar Physics, 8, 6Sinha, S., Srivastava, N., & Nandy, D. 2019, ApJ, 880, 84Su, J., Liu, Y., Kurokawa, H., et al. 2007, Sol. Phys., 242, 53Sterling, A. C., Moore, R. L., & Freeland, S. L. 2011, ApJ, 731, L3Sun, J. Q., Cheng, X., Ding, M. D., et al. 2015, Nature Communications, 6, 7598T¨or¨ok, T., Chandra, R., Pariat, E., et al. 2011, ApJ, 728, 65T¨or¨ok, T., Panasenco, O., Titov, V. S., et al. 2011, ApJ, 739, L63Wang, D., Liu, R., Wang, Y., et al. 2018, ApJ, 869, 177 13 –Wang, H., Chae, J., Yurchyshyn, V., et al. 2001, ApJ, 559, 1171Wang, R., Liu, Y. D., Zimovets, I., et al. 2016, ApJ, 827, L12
Wheatland, M. S., Sturrock, P. A., & Roumeliotis, G. 2000, ApJ, 540, 1150Wiegelmann, T. 2004, Sol. Phys., 219, 87
Woods, M. M., Inoue, S., Harra, L. K., et al. 2018, ApJ, 860, 163Yang, B., & Chen, H. 2019, ApJ, 874, 96Yang, J., Jiang, Y., Zheng, R., et al. 2012, ApJ, 745, 9Yang, L., Yan, X., Li, T., Xue, Z., & Xiang, Y. 2017, ApJ, 838, 131Yang, S., & Zhang, J. 2018, ApJ, 860, L25Zaitsev, V. V., & Stepanov, A. V. 2018, Journal of Atmospheric and Solar-Terrestrial Physics,179, 149Zhang, J., Wang, J., & Nitta, N. 2001, Chinese J. Astron. Astrophys., 1, 85Zheng, R., Zhang, Q., Chen, Y., et al. 2017, ApJ, 836, 160Zirker, J. B., Martin, S. F., Harvey, K., & Gaizauskas, V. 1997, Sol. Phys., 175, 27
This preprint was prepared with the AAS L A TEX macros v5.2.
14 – (a) H α F2F1 S o l a r Y ( a rc s ec ) (b) AIA 171 Å 21:45:10 UT F2F1 (c) HMI Mag. 21:43:56 UT + −+
AR 12449AR 12450AR 12452
Fig. 1.— Overview of the two filaments on 2015 November 15. Panel (a): H α image. Thegreen square in panel (a) outlines the FOVs of panels (a)-(b) in Figure 2, panels (a1)-(a3)and (b1)-(b3) in Figure 4 and, Figure 5. Panel (b): AIA 171 ˚A image. Panel (c): HMILOS magnetogram. The two white dashed curves in panels (b)-(c) show the approximatelocations of the two nearby filaments before eruptions. 15 – (a) AIA 193Å 17:00:05 UT S o l a r Y ( a rc s ec ) (b)HMI Mag 16:58:56 UT1 2 34 F1 (c1) AIA 193Å 17:00:05 UT (c2) AIA 193Å 20:45:05 UT (c3) AIA 193Å 22:15:05 UT(d1) HMI Mag 16:58:56 UT
40 80 120 160Solar X (arcsec)−440−400−360−320 S o l a r Y ( a rc s ec ) (d2) HMI Mag 20:43:56 UT AB (d3) HMI Mag 22:13:56 UT (e) S li ce A − B ( a rc s ec ) Fig. 2.— AIA 193 ˚A images and HMI LOS magnetograms showing the emission brighteningand flux cancellation near the barbs of F1. Panels (a) and (b): 193 ˚A image and HMImagnetogram showing the sites of brightening and flux cancellation. Panels (c1)-(d3): Timesequences of 193 ˚A images and HMI magnetograms showing the temporal evolution of thebrightening and flux cancellation, respectively. The white and green squares correspond tothe green box “2” in panel (b). The green curve in panel (c3) is the contour of emissionstrength in 193 ˚A wavelength. Panel (e): Time-slice plot of magnetograms along the cut“A-B” marked in panel (d2). The animation shows the brightening and flux cancellationevolving from 17:00 to 22:50 UT on 2015 November 15. 16 – (a1) AIA 304 Å 21:01:06 UT S o l a r Y ( a rc s ec ) F1 (a2) AIA 304 Å 22:33:06 UT C DRising F1 (a3) AIA 304 Å 23:06:06 UT (b1) S li ce C − D ( a rc s ec ) ~110 km/s AIA 304 Å (b2) ~96 km/s
AIA 171 Å (b3) ~102 km/s
AIA 131 Å
Fig. 3.— Images of AIA 304 ˚A and time-slice plots showing the eruption of F1. Panels (a1)-(a3): Time sequences of 304 ˚A images. The green arrows in panel (a2) denote the projectedmoving directions of F1. The green dotted curves in panel (a3) exhibit two flare ribbonscaused by F1 eruption. The line “C-D” in panel (a2) marks the position of time-slice plotsin panels (b1)-(b3). Panels (b1)-(b3): Time-slice plots of 304 ˚A, 171 ˚A, and 131 ˚A imagesdisplaying the temporal evolution of F1. The dashed curves approximate the tracks of F1 indifferent wavelength images. The green curve in panel (b1) is the 193 ˚A light curve in theregion marked by the green curve in Figure 2(c3). The vertical white dotted line in panel(b1) indicates the time of emission reaching at the peak (the onset of F1 eruption). Theanimation shows the eruption process of F1 from 22:10 to 23:28 UT on 2105 November 15. 17 – (a1) AIA 304 Å 21:01:06 UT
F1F2 S o l a r Y ( a rc s ec ) (a2) AIA 304 Å 23:01:06 UT F2Ribbons S o l a r Y ( a rc s ec ) (a3) AIA 304 Å 23:52:06 UT F2 S o l a r Y ( a rc s ec ) (b1) AIA 304 Å 00:18:06 UT F2FRF1 S o l a r Y ( a rc s ec ) (b2) AIA 304 Å 01:16:06 UT Rising F2FRF1EF S o l a r Y ( a rc s ec ) (b3) AIA 304 Å 02:00:06 UT FRF1Erupting F2 S o l a r Y ( a rc s ec ) (c1) ~3 km/s S li ce E − F ( a rc s ec ) ~120 km/s t1 t2 AIA 304 Å (c2) ~3 km/s S li ce E − F ( a rc s ec ) ~120 km/s t1 t2 AIA 171 Å (c3) ~3 km/s S li ce E − F ( a rc s ec ) ~120 km/s t1 t2 AIA 131 Å
Fig. 4.— The temporal evolution of FRF1 spreading, interaction between FRF1 and F2,and F2 eruption. Panels (a1)-(a3): Time sequences of 304 ˚A images showing the expansionof the flare ribbons formed by F1 eruption. In panel (a1), the approximate locations ofF1 and F2 before their eruptions are outlined by white dashed curves. The green dottedcurves in panels (a2)-(a3) display the separating flare ribbons related to F1 eruption. Thegreen arrows in panels (a2)-(a3) indicate the spreading direction of the southwestern ribbon.Panels (b1)-(b3): Time sequences of 304 ˚A images displaying the lifting and eruption of F2by the intrusion of the southwestern flare ribbon (FRF1) related to erupting F1. The greenarrow in panel (b1) denotes the location where FRF1 reached and intruded F2. The line“E-F” in panel (b2) marks the position of time-slice plots in panels (c1)-(c3). Panels (c1)-(c3): time slices of AIA 304˚A, 171 ˚A, and 131 ˚A images revealing the temporal evolution ofF2. The animation shows the spreading of FRF1, interaction between FRF1 and F2, andF2 eruption from 00:00 to 02:00 UT on 2015 November 16. 18 – (a1) AIA 304 Å 02:12:06 UT
FRF1 FRF2 (a2) AIA 304 Å 02:28:06 UT
FRF1 FRF2 (a3) AIA 304 Å 03:00:06 UT
FRF1 FRF2 (b1) AIA 171 Å 05:00:10 UT S o l a r Y ( a rc s ec ) (b2) AIA 131 Å 05:00:07 UT (b3) AIA 211 Å 05:00:07 UT Fig. 5.— The temporal evolution of FRF2 and post-flare loops after F2 eruption. Panels(a1)-(a3): Time sequences of AIA 304 ˚A images showing the process of the northern ribbon(FRF2; white dotted curves) related to F2 eruption approaching the southwestern ribbon(FRF1; green dotted curves) formed by F1 eruption. Panels (b1)-(b3): AIA 171 ˚A, 131 ˚A,and 211 ˚A images displaying the post-flare loops caused by the eruptions of F1 and F2. Thered and blue curves in panel (b1) are contours of corresponding HMI LOS magnetic fieldswith positive and negative polarity, respectively. The contour levels are ±
50 Gauss. Thewhite and green arrows in panels (b1)-(b3) indicate the post-flare loops formed after F1 andF2 eruptions, respectively. The dashed curves in panel (b2) denote the approximate locationsof F1 and F2 before their eruptions. The white and dash-dotted squares in all panels outlinetwo different regions of northwest and southeast of F2, respectively. The animation showsthe formation and spreading of FRF2, and the post-flare loops caused by the eruptions ofF1 and F2 from 02:00 to 04:59 UT on 2015 November 16. 19 – a S o l a r Y ( Mm ) −5000500 B z ( G ) b H e i gh t ( Mm ) D e c a y i nde x ( n ) D e c a y i nde x ( n ) c Fig. 6.—