aa r X i v : . [ a s t r o - ph . S R ] M a y Astronomy&Astrophysicsmanuscript no. ms c (cid:13)
ESO 2018August 23, 2018
Blobs in recurring EUV jets
Q. M. Zhang and H. S. Ji
Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, CAS, Nanjing210008, Chinae-mail: [email protected]
Received; accepted
ABSTRACT
Context.
Coronal jets are one type of ubiquitous small-scale activities caused by magnetic recon-nection in the solar corona. They are often associated with cool surges in the chromosphere.
Aims.
In this paper, we report our discovery of blobs in the recurrent and homologous jets thatoccurred at the western edge of NOAA active region 11259 on 2011 July 22.
Methods.
The jets were observed in the seven extreme-ultraviolet (EUV) filters of theAtmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory(SDO). Using the base-di ff erence images of the six filters (94, 131, 171, 211, 193, and 335 Å),we carried out the di ff erential emission measure (DEM) analyses to explore the thermodynamicevolutions of the jets. The jets were accompanied by cool surges observed in the H α line centerof the ground-based telescope in the Big Bear Solar Observatory. Results.
The jets that had lifetimes of 20 −
30 min recurred at the same place for three times withinterval of 40 −
45 min. Interestingly, each of the jets intermittently experienced several upwarderuptions at the speed of 120 −
450 km s − . After reaching the maximum heights, they returnedback to the solar surface, showing near-parabolic trajectories. The falling phases were more ev-ident in the low- T filters than in the high- T filters, indicating that the jets experienced coolingafter the onset of eruptions. We identified bright and compact blobs in the jets during their risingphases. The simultaneous presences of blobs in all the EUV filters were consistent with the broadranges of the DEM profiles of the blobs (5 . ≤ log T ≤ . ∼ ∼ −
60 s.
Conclusions.
To our knowledge, this is the first report of blobs in coronal jets. We propose thatthese blobs are plasmoids created by the magnetic reconnection as a result of tearing-mode insta-bility and ejected out along the jets.
Key words.
Sun: chromosphere – Sun: corona – Sun: activity
1. Introduction
Coronal jets are transitory X-ray or extreme-ultraviolet (EUV) enhancements with an apparent col-limated motion (Shibata et al. 1992). They were first observed by the Soft X-ray Telescope (SXT)aboard Yohkoh (Tsuneta et al. 1991). More and more coronal jets were observed by space-bornetelescopes with higher resolutions and time cadences in the last two decades (Chae et al. 1999;Savcheva et al. 2007; Chifor et al. 2008; Nistic`o et al. 2009; Shen et al. 2012; Moschou et al. 2012;
1. M. Zhang & H. S. Ji: Blobs in EUV jets
Lee et al. 2013; Jiang et al. 2013). It is widely accepted that coronal jets are heated by magneticreconnection between emerging flux and the pre-existing magnetic fields with opposite polarity(Shibata & Uchida 1986; Yokoyama & Shibata 1996; Moreno-Insertis et al. 2008; T¨or¨ok et al.2009; Moreno-Insertis & Galsgaard 2013). According to the numerical simulations of Yokoyama& Shibata (1996), there are hot, compact microflares at their footpoints (Krucker et al. 2011; Zhang& Ji 2013) and cool H α surges adjacent to the hot jets (Schmieder et al. 1995; Canfield et al. 1996;Liu & Kurokawa 2004; Jiang et al. 2007; Liu 2008; Nelson & Doyle 2013). The EUV emissionsfrom a hot jet were observed to be absorbed by the foreground cool surge, resulting in EUV dim-ming behind the leading edge of the jet (Zhang & Ji 2014). Pariat et al. (2009) proposed a newmechanism for the coronal hole jets as a result of continuous pumping of magnetic free energy aswell as helicity into the upper solar atmosphere. The presence of dome-like magnetic topology thatconsists of a null point, a spine, and a separatrix surface in a X-ray bright point associated withrecurrent jets was observed and reported by Zhang et al. (2012). Coronal jets are usually generatedin coronal holes (Cirtain et al. 2007; Culhane 2007; Patsourakos et al. 2008; Chandrashekhar et al.2014) or at the edge of active regions (Kim et al. 2007; Guo et al. 2013; Schmieder 2013; Zhang &Ji 2014). The apparent heights and widths of jets are 10 −
400 Mm and 5 −
100 Mm. The velocitiesof jets are 10 − − , which are the same order of magnitude as the coronal Alfv´en speed(Shimojo et al. 1996).Recurrent jets and surges have often been observed and extensively been studied thanks to theeverlasting development and improvement of the solar telescopes. Chae et al. (1999) analysed si-multaneous EUV data and H α data from BBSO. Several EUV jets repeatedly occurred in the activeregion where pre-existing magnetic flux was canceled by newly emerging flux of opposite polar-ity. Chifor et al. (2008) analysed a recurring solar active region jet observed in X-ray and EUV,finding a correlation between recurring magnetic cancellation and the X-ray jet emission. The jetemission was attributed to chromospheric evaporation flows due to recurring magnetic reconnec-tion. Recurrent jets can also be caused by moving magnetic features (Brooks et al. 2007; Yang etal. 2013). Guo et al. (2013) reported the discovery of three EUV jets recurring in about one houron 17 September 2010. According to the nonlinear force-free field extrapolation, the authors con-cluded that the magnetic reconnection occurred periodically in the current layer created betweenthe emerging bipoles and the large-scale active region field, inducing the observed recurrent coronaljets. Murray et al. (2009) performed MHD numerical simulations of interaction between emergingflux and pre-existing magnetic fields in a coronal hole. When gas pressure of the reconnection out-flow region exceeds that of the inflow region, the magnetic field lines in the two bounded outflowregions are driven to reconnect reversely, giving rise to an oscillatory reconnection and recurrentjets with the peak magnetic reconnection rate decreasing as time goes on. Pariat et al. (2010) per-formed 3D MHD simulations of periodic coronal jets due to continuous twisting motion of thephotosphere and pumping of magnetic free energy.The temperatures of coronal jets have been extensively investigated since their discovery. Thereare mainly two methods for temperature diagnostics. One is filter-ratio assuming single temperaturealong the line-of-sight (LOS). It has been applied using the EUV 171 Å, 195 Å, and 284 Å filtersor broad-band soft X-ray filters (e.g., Shimojo & Shibata 2000; Nistic`o et al. 2011; Madjarska2011; Madjarska et al. 2012; Matsui et al. 2012; Pucci et al. 2013; Young & Muglach 2013). Thisapproach, however, has its limitation and weakness. The reliable temperatures are limited within
2. M. Zhang & H. S. Ji: Blobs in EUV jets the monotonic range of the ratio of the temperature response functions of the two employed filters.The calculated temperature may represent the average temperature of the plasmas along the LOS.The other method is di ff erential emission measure (DEM) based on the multi-thermal nature of theplasmas along the LOS (Doschek et al. 2010; Chandrashekhar 2013; Kayshap et al. 2013; Chenet al. 2013; Sun et al. 2014b), which is more realistic and reasonable. Occasionally, hard X-ray(HXR) sources could be detected at the bottom of jets, and the hot thermal component could beisolated during the fittings to perform temperature diagnostic (Bain & Fletcher 2009; Krucker etal. 2011; Glesener et al. 2012). The temperatures of jets are 0.5 − −
30 MK) at the bottom, which have been reproduced in the multi-dimensionalmagnetohydrodynamic (MHD) numerical simulations (Nishizuka 2008; Archontis & Hood 2013).Blob-like features or plasmoids are ubiquitous in the solar atmosphere. During the magneticreconnections involved in solar flares, the electric current sheet may subject to the tearing-modeinstability (Furth et al. 1963), leading to the formation of multiple magnetic islands or plasmoidsthat are bidirectionally ejected out of the di ff usion region (Ohyama & Shibata 1998; Kliem et al.2000; Ko et al. 2003; Asai et al. 2004; Lin et al. 2005; Kołoma´nski & Karlick´y 2007; B´arta etal. 2008; Nishizuka et al. 2010; Milligan et al. 2010; Takasao et al. 2012; Ni et al. 2012a, 2012b;Kumar & Cho 2013). The plasmoid velocity is found to have a positive correlation with the recon-nection rate (Nishida et al. 2009). White-light blobs are observed to be quasi-periodically ejectedout of the large-scale coronal streamers (Song et al 2009). Recurrent plasmoids in the chromo-spheric anemone jets with size of ∼
2. Data analysis
There are seven EUV filters (94, 131, 171, 193, 211, 304, and 335 Å) aboard the SDO / AIA in-strument to achieve a wide temperature coverage (5 . ≤ log T ≤ . − . ′′
2. The level 1 fits data were calibrated using the standard program aia prep.pro in the Solar Software. The images observed in di ff erent wavelengths were coalignedcarefully using the cross-correlation method. Fortunately, the hot EUV jets were accompanied bycool H α surges observed by the ground-based telescopes in Big Bear Solar Observatory (BBSO)with time cadence of 85 −
100 s and resolution of 2 ′′ . The H α images were coaligned with the 304Å images.The observed intensity of an optically thin EUV line i is defined as I i = R T T ( d EM / dT ) R i ( T ) dT ,where log T = . T = . R i ( T ) denotes the temperature response function of line i , and EM = R n e dh repre-sents the total column emission measure along the LOS. Here, n e stands for the electron num-
3. M. Zhang & H. S. Ji: Blobs in EUV jets ber density. Therefore, DEM = d EM / dT = n e dh / dT means the di ff erential emission measure.The DEM-weighted average temperature of the plasma along the LOS T e f f = R T T DEM × T × dT / R T T DEM dT = R T T DEM × T × dT / EM. A couple of methods and programs have been devel-oped to reconstruct the DEM profiles using a set of EUV or SXR filters (e.g., Golub et al. 2004;Weber et al. 2004, 2005; Hannah & Kontar 2012; Aschwanden et al. 2013). Using six of the AIAfilters (94, 131, 171, 211, 193, and 335 Å), Cheng et al. (2012) derived the DEM profiles and aver-age temperatures of the three components of a coronal mass ejection (CME; Chen 2011) observedby SDO: hot channel in the core region, the bright loop-like leading front, and coronal dimming inthe wake of the CME (Cheng et al. 2013; Hannah & Kontar 2013). Recently, this method has alsobeen applied to the temperature diagnostics of solar flares (Sun et al. 2014a) as well as failed fila-ment eruption (Song et al. 2014). Since the jets were quite close to the active region, we selectedthe images before the onsets of the jets as base images and derived the base-di ff erence imagesduring the jets so that the emissions and influences of the background corona were removed. Weused the base di ff erence images and the same method to reconstruct the DEM profiles and studythe thermodynamic evolutions of the recurring jets. To evaluate the confidence in the reconstructedDEMs, we conducted Monte Carlo (MC) simulations described in detail in Cheng et al. (2012).The chi-square ( χ ) of the 100 MC simulations is a measure of scatter of the DEM profiles. Lowervalues of χ mean smaller uncertainties in the DEM solution.
3. Results
There were three recurrent and homologous EUV jets. The first jet (jet1) started at ∼ ∼ Y -shaped coronal jets. However, a bright kernelvisible in all the EUV wavelengths was ejected upwards along the jet as pointed by the whitearrows.In order to study the longitudinal evolution of the jet, we extracted the intensity along the jetaxis, which is labeled with “cut1” (75 ′′ in length) and indicated by the white dashed line in Fig. 1d.The time-slice diagrams of cut1 in the seven EUV wavelengths are displayed in Fig. 2. It is revealedthat jet1 underwent two main eruptions at the speed of ∼
435 km s − and ∼
136 km s − (Fig. 2d),followed by two weak and short eruptions that are more obvious in 171 Å (Fig. 2e) and 131 Å(Fig. 2f). The velocities of the two weak short eruptions were 271 km s − and 123 km s − . Thelength of the jet reached maximum (35.6 Mm) at ∼ ∼ (e) and (f) in Fig. 2). The near-parabolic trajectory and the fallingphase of the jet are more evident in the low- T filters (see panels (e) , (f) , and (g) in Fig. 2) than inthe high- T filters (see panels (b) , (c) , and (d) in Fig. 2). Such trajectory, similar to the case reportedby Zhang & Ji (2014), indicates that the hot EUV jets underwent cooling owning to radiative lossand thermal conduction. The lifetime of jet1 is ∼
24 min.
4. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 1.
Snapshots of jet1 seen in the six EUV filters at ∼ (a) , (b) , (c) , (e) , and (f) . The white dashed line labeled with “cut1”in panel (d) is used to investigate the longitudinal evolution of the jet whose time-slice diagram isdisplayed in Fig. 2. The temporal evolution of jet1 is shown in a movie ( jet1.avi ) available in theonline edition.About a quarter after the end of jet1, the second collimated jet (jet2) occurred at the same placeas the previous one. The bottom of the jet was composed of a couple of tiny bright kernels ratherthan a typical two-chamber structure. It started at ∼ ∼ ∼ ∼ ff used than jet1. There was also a compact and bright feature within jet2, which is pointed by thearrows.We extracted the intensity along the axis of jet2, which is labeled with “cut2” (71 ′′ in length)and indicated by the white dashed line in Fig. 3d. The time-slice diagrams of cut2 in the seven filtersare shown in Fig. 4. Starting at 22:07 UT, jet2 experienced a series of quasi-periodic eruptions withperiod of ∼
65 s until 22:17 UT at the speed of ∼
311 km s − , which are illustrated by the multiplewhite dashed dotted lines in Fig. 4e. Like jet1, jet2 also presented near-parabolic trajectory, i.e.,
5. M. Zhang & H. S. Ji: Blobs in EUV jets
Table 1.
Parameters of the three EUV jets
No. Height Width Velocity Lifetime(Mm) (Mm) (km s − ) (min)1 26.8 2.9 123 −
435 242 23.7 5.4 ∼
311 283 12.8 2.8 ∼
311 20 plasma fell back to the solar surface after reaching the maximum height (31.7 Mm). The fallingphase that ended at 22:35 UT was most distinct in the low- T wavelengths (see panels (e) , (f) , and (g) ).After 22:52 UT, the third homologous jet (jet3) appeared, but with much shorter length andweaker intensity compared with the previous jets. Fig. 5 shows snapshots of the jet in the six filtersat ∼ ′′ in length) andindicated by the white dashed line in Fig. 5d. The time-slice diagrams of cut3 in the seven filters aredisplayed in Fig. 6. Like the previous jets, jet3 underwent intermittent eruptions, which are denotedby the white dotted lines in Fig. 6e, and reached maximum height ( ∼ ∼
311 km s − . The near-parabolictrajectory of jet3 is clearly illustrated in the 131, 193, 171, and 304 Å images. The parameters ofthe three EUV jets are summarised in Table 1, including the maximum apparent heights, widths,apparent rising velocities, and lifetimes. From the online movies that illustrate the evolutions of the recurrent jets, we identified more blobs.Fig. 7 shows nine snapshots of the 171 Å images during jet1. The bright and compact kernelsas pointed by the white arrows moved upwards from the bottom to the top of the jet during21:30:12 − ∼ − −
60 s). Panels (d) − (f) illustrate the rising motion of a blobfrom the middle to top of the jet. Panels (h) − (i) show a blob that was restricted near the bottom ofthe jet.Figure 9 displays nine snapshots of the 171 Å images during jet3. Compared with the previoustwo jets, the blobs were much fainter and reached lower heights. Panels (b) − (d) reveal that theblobs were close to the bottom of jet. Panels (e) − (i) illustrate the complete evolution of a blob.It appeared at 22:55:00 UT and reached maximum brightness at 22:55:12 UT before graduallymixing with the surroundings and fading out after 22:55:48 UT.
6. M. Zhang & H. S. Ji: Blobs in EUV jets
We performed DEM analyses and derived the two-dimensional (2D) distributions of the EMand temperature ( T e f f ) of the jets. Note that the minimum and maximum temperatures ( T and T )for the integral of EM are 10 . K and 10 . K. In Fig. 10, the top two rows demonstrate the selectedEM and T e f f maps of the jets during the rising phases of jet1 ( left ), jet2 ( middle ), and jet3 ( right ),respectively. The jets and blobs pointed by the yellow arrows are clearly present in the maps withhigher emissions and temperatures than the adjacent quiet region. The two-chamber base of jet1and the cusp-like bases of jet2 and jet3 with the highest emissions and temperatures are also clearlydemonstrated in the maps. The bottom two rows demonstrate the selected EM and T e f f maps ofthe jets during the falling phases of jet1 ( left ), jet2 ( middle ), and jet3 ( right ), respectively. It is seenthat the emissions of the jets got quite weak and the temperatures decreased to a low level close tothe adjacent quiet region, which is consistent with the time-slice diagrams of the jets in Figs. 2, 4,and 6.In the top panels of Fig. 10, the core regions of blobs are included in the small yellow boxeswith sizes of 1.8 ′′ . The base-di ff erence EUV intensities within the boxes were averaged so that thecore regions were taken as a whole. The DEM profiles of the first, second, and third blob cores aredisplayed in the top, middle, and bottom panels of Fig. 11, respectively. The red solid lines standfor the best-fitted profiles derived from the observed values, while the black dashed lines representthe profiles derived from the 100 MC simulations. It is obvious that the DEM profiles have a broadrange between 5 . ≤ log T ≤ .
5, indicating that the blobs are multi-thermal in nature. However,the contributions of EM come mainly from the low- T plasma since the DEM decreases with log T .The reconstructions of the curves are most accurate and reliable in the range of 5 . ≤ log T ≤ . . ≤ log T ≤ .
5. The median values of the χ in the orders of 20 are labeled in Fig. 11. The T e f f of the blob core regions of jet1, jet2, andjet3 are 2.2, 2.7, and 3.3 MK. The corresponding log EM are 27.5, 27.0, and 27.1, respectively. Theaverage electron number densities of the blobs n e were estimated according to √ EM / H (assumingfilling factor ≈ n e for the three blobs are 3.3, 1.9, and 2.1 × cm − , respectively. However, such estimations usingthe imaging data are very qualitative due to the large uncertainties of the plasma filling factor aswell as the LOS column depth of the blobs. Considering the favorable perspectives of the SolarTerrestrial Relation Observatory (STEREO; Kaiser et al. 2005), we tried to find the counterpartsof the jets in the EUV images observed by STEREO but failed due to the small scales and weakintensities of the jets. More precise diagnostics of the plasma densities should be conducted usingthe spectra-imaging observations.We also derived the DEM curves of the blobs in jet1, jet2, and jet3 during their lifetimes. Theyare similar to those displayed in Fig. 11, featuring broad distributions and decreasing trends withtemperature. Base on the DEM curves, we calculated the temperatures of the blobs in the threerecurrent jets. The T e f f ranges from 0.5 to 4 MK with an median value of 2.3 MK.
7. M. Zhang & H. S. Ji: Blobs in EUV jets
4. Discussion
Despite of their small scales, coronal jets usually present various morphology and characteristics.Nistic`o et al. (2009) classified the 79 polar jets into four catalogues: Ei ff el Tower-type jets, λ -type jets, micro-CME-type, and others. Based on the physical mechanisms, Moore et al. (2010)classified polar jets into standard and blowout jets. The former are the same as the well-knowninverse- Y jets. The latter are counterparts of erupting-loop H α macrospicules, where the jet-basemagnetic arch undergoes a miniature version of the blowout eruptions that produce major CMEs.The main di ff erences lie in whether the base arches have enough shear and twist to erupt open.Moore et al. (2013) carried out in-depth comparison and found that the blowout jets statisticallyhave cool component seen in 304 Å, lateral expansion, and axial rotation. The recurrent jets in ourstudy matched the standard type according to their morphology. However, they were present inall the EUV wavelengths of AIA, including the cool filters (304 Å). Lateral expansion and axialrotation, however, were absent in the jets. We have not noticed signatures of CME-like eruptionsfrom the jet bases or curtain-like shapes after their eruptions as in the blowout jets. Therefore, wepropose that the recurrent jets belong to the standard type though they had cool component. Coronal jets are always observed in the EUV and X-ray wavelengths, while surges are often ob-served in H α due to their cool nature. According to the numerical simulations of Yokoyama &Shibata (1996), both hot (10 − K) and cool ( ∼ K) plasma ejections are created side byside during the magnetic reconnection between the emerging flux and the pre-existing magneticfields. The spatial relationship between the jets and surges is controversial. It has been observedthat surges are adjacent to jets (Canfield et al. 1996; Chae et al. 1999; Jiang et al. 2007). In ourstudy, the hot jets observed in the AIA filters were associated with recurrent cool surges observedand covered during their whole lifetimes in the H α line center (Wang et al. 2014). In Fig. 12, wecompared the 304 Å ( left panels ) and H α ( right panels ) images that represent the three jets fromtop to bottom rows, respectively. We also superpose the intensity contours of the H α images on thecorresponding EUV images, finding that the surges were cospatial with the EUV dimmings behindthe leading edges of the jets. After examining the movies of the recurrent jets in the other six EUVfilters, we found that the dimmings visible in all the filters were cospatial with the surges. In theswirling flare-related jet on 2011 October 15 at the edge of AR 11314, Zhang & Ji (2014) discov-ered EUV dimming behind the leading edge of the jet, which was explained by the absorption ofthe EUV emissions of the hot jet by the foreground cool surge. Such explanation could be convinc-ingly justified by our detailed and complete case study of recurrent jets. Considering that the jetsand surges are 3D in nature (Moreno-Insertis & Galsgaard 2013), we believe that the di ff erences ofspatial relationship between the jet and surge lie in the di ff erent perspectives of observation. Whenthe LOS is perpendicular to the plane determined by the jet and surge, they are adjacent to eachother. However, when the LOS is parallel to the plane, they are cospatial and the EUV and X-rayemissions of the jets may be absorbed by the surges.
8. M. Zhang & H. S. Ji: Blobs in EUV jets
The magnetic islands or plasmoids associated with solar flares have extensively been observedand studied. Asai et al. (2004) discovered bursty sunward motions above the post-flare loops. Theauthors interpreted the bursty downflow as many plasmoids created inside the current sheet inducedby the eruption of the large-scale filament. The velocities of the downflow were 45 −
500 km s − ,the electron number densities were 1 − × cm − , and the sizes were 2 −
10 Mm. In our case, therising velocities of the blobs in the jets were 120 −
450 km s − , which were close to the values ofthe plasmoids associated with the big flare. The sizes ( ∼
5. Summary
In this paper, we studied the recurrent and homologous jets that took place at the western edgeof AR 11259 on 2011 July 22. The jets that had lifetimes of 20 −
30 min recurred for three timeswith interval of 40 −
45 min. Quasi-periodic eruptions were observed during each of the jets at thespeed of 120 −
450 km s − . After reaching the maximum heights, the jet plasmas returned backto the solar surface, showing near-parabolic trajectories. The falling phases were more evidentin the low- T filters than in the high- T filters, indicating that the jets experienced cooling due toradiative loss and thermal conduction after the onset of eruptions. We identified very bright andcompact features, i.e., blobs, in the jets during their rising phases. The simultaneous presences ofblobs in all the EUV filters are consistent with the broad ranges of the DEM profiles of the blobs,indicating their multi-thermal nature. The DEM-weighted average temperatures of the blobs rangefrom 0.5 to 4 MK with a median value of ∼ −
60 s. Toour knowledge, this is the first report of blobs in coronal jets, and their physical properties are quiteclose to those of the bidirectionally ejected plasmoids during big flares, suggesting that the basicprocess of tearing-mode instability in current sheets exists not only in the large-scale solar flaresbut also in small-scale jets. Additional case studies and numerical simulations are required to get abetter understanding of the blobs.
Acknowledgements.
The authors are grateful to the referee for the enlightening and valuable comments. Q.M.Z acknowl-edges X. Cheng, T. H. Zhou, Y. N. Su, B. Kliem, L. Ni, P. F. Chen, M. D. Ding, C. Fang, R. Moore, E. Pariat, and thesolar physics group in Purple Mountain Observatory for discussions and suggestions. SDO is a mission of NASA’s LivingWith a Star Program. AIA and HMI data are courtesy of the NASA / SDO science teams. The H α data were obtained fromthe Global High Resolution H α Network operated by the Big Bear Solar Observatory, New Jersey Institute of Technology.This work is supported by 973 program under grant 2011CB811402 and by NSFC 11303101, 11333009, 11173062 and11221063.
9. M. Zhang & H. S. Ji: Blobs in EUV jets
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10. M. Zhang & H. S. Ji: Blobs in EUV jets
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11. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 2.
Time-slice diagrams of cut1 in the seven filters during jet1. The white dotted lines in panel (d) signify the two major eruptions of the jet, with the slopes representing the rising speeds of 435km s − and 136 km s − , respectively. The major eruptions were followed by two weak and shorteruptions illustrated by white dotted lines and pointed by the white arrows in panels (e) and (f) . Theslopes of the short dotted lines represent the velocities of the eruptions, being 271 km s − and 123km s − , respectively. The near-parabolic trajectory of the jet is more evident in the low- T filters(131, 171, and 304 Å) than in the high- T filters (211, 193, and 335 Å). Note the possible post-jetbrightenings around 21:52 UT in panels (e) and (f) .
12. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 3.
Snapshots of jet2 seen in the six filters at ∼ (a) , (b) , (c) , (e) , and (f) . The white dashed line labeled with “cut2”in panel (d) is used to investigate the longitudinal evolution of the jet whose time-slice diagram isdisplayed in Fig. 4. The temporal evolution of jet2 is shown in a movie ( jet2.avi ) available in theonline edition.
13. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 4.
Time-slice diagrams of cut2 in the seven filters during jet2. It experienced quasi-periodicupward eruptions with period of ∼
65 s during 22:07 − ∼
311 km s − , whichis indicated by the white dotted lines in panel (e) .
14. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 5.
Snapshots of jet3 seen in the six filters at ∼ (b) , (e) , and (f) . The white dashed line labeled with “cut3” in panel (d) isused to investigate the longitudinal evolution of the jet whose time-slice diagram is displayed inFig. 6. The temporal evolution of jet3 is shown in a movie ( jet3.avi ) available in the online edition.
15. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 6.
Time-slice diagrams of cut3 in the seven filters during jet3. The white dotted lines in panel (e) illustrate the intermittent eruptions of jet3 during 22:52 − − .
16. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 7. (a) − (i) Nine snapshots of the AIA 171 Å images, showing the blobs during jet1 as pointedby the white arrows.
17. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 8. (a) − (i) Nine snapshots of the AIA 171 Å images, showing the blobs during jet2 as pointedby the white arrows.
18. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 9. (a) − (i) Nine snapshots of the AIA 171 Å images, showing the blobs during jet3 as pointedby the white arrows.
19. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 10.
Top two rows : EM (a − c) and temperature maps (d − f) of the jets during their rising phases.The arrows point to the blobs in the jets. The DEM curves of the plasmas in the boxes of (a − c) are displayed in Fig. 11. Bottom two rows : EM (g − i) and temperature maps (j − l) of the jets duringtheir falling phases. Note that EM and T e f f are in log-scales.
20. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 11.
DEM profiles of the blob core regions of jet1 (a) , jet2 (b) , and jet3 (c) indicated in thetop panels of Fig. 10. The red solid lines stand for the best-fitted DEM curves from the observedvalues. The black dashed lines represent the reconstructed curves from the 100 MC simulations.The corresponding EM, T e f f of the blobs, and the median values of χ of the MC simulations aredisplayed.
21. M. Zhang & H. S. Ji: Blobs in EUV jets
Fig. 12.
Left panels : AIA 304 Å images during jet1 (a) , jet2 (c) , and jet3 (e) . The arrows point to theleading edges of the jets and the following dimming regions.
Right panels : The near-simultaneousH α images of the same FOV. The intensity contours of the H α images are overlaid on the corre-sponding 304 Å images.images are overlaid on the corre-sponding 304 Å images.