Transverse vertical oscillations during the contraction and expansion of coronal loops |
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Qingmin Zhang Submitted: 2023-05-15 19:21
In this paper, we carry out a detailed analysis of the M1.6 class eruptive flare occurring in NOAA active region 13078 on 2022 August 19. The flare is associated with a fast coronal mass ejection (CME) propagating in the southwest direction with an apparent speed of ∼926 km s-1. Meanwhile, a shock wave is driven by the CME at the flank. The eruption of CME generates an extreme-ultraviolet (EUV) wave expanding outward from the flare site with an apparent speed of ~200 km s-1. As the EUV wave propagates eastward, it encounters and interacts with the low-lying adjacent coronal loops (ACLs), which are composed of two loops. The compression of EUV wave results in contraction, expansion, and transverse vertical oscillations of ACLs. The commencements of contraction are sequential from western to eastern footpoints and the contraction lasts for ~15 minutes. The speeds of contraction lie in the range of 13-40 km s-1 in 171 Å and 8-54 km s-1 in 193 Å. A long, gradual expansion follows the contraction at lower speeds. Concurrent vertical oscillations are superposed on contraction and expansion of ACLs. The oscillations last for 2-9 cycles and the amplitudes are ≤4 Mm. The periods are between 3 to 12 minutes with an average value of 6.7 minutes. The results show rich dynamics of coronal loops.
Authors: Qingmin Zhang, Yuhao Zhou, Chuan Li, Qiao Li, Fanxiaoyu Xia, Ye Qiu, Jun Dai, Yanjie Zhang
Projects: SDO-AIA
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Publication Status: Accepted for publication in ApJ
Last Modified: 2023-05-17 13:09
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Rapid Rotation of an Erupting Prominence and the Associated Coronal Mass Ejection on 13 May 2013 |
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Qingmin Zhang Submitted: 2023-02-01 20:53
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-1, respectively. The total twist angle reaches ~7π, 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 Å and STEREO-B/EUVI in 304 Å 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.
Authors: Yuhao Zhou, Haisheng Ji, Qingmin Zhang
Projects: SoHO-LASCO
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Publication Status: accepted for publication in Solar Physics
Last Modified: 2023-02-04 18:51
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First detection of transverse vertical oscillation during the expansion of coronal loops |
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Qingmin Zhang Submitted: 2022-09-01 20:07
In this Letter, we perform a detailed analysis of the M5.5-class eruptive flare occurring in active region 12929 on 2022 January 20. The eruption of a hot channel generates a fast coronal mass ejection (CME) and a dome-shaped extreme-ultraviolet (EUV) wave at speeds of 740-860 km s-1. The CME is associated with a type II radio burst, implying that the EUV wave is a fast-mode shock wave. During the impulsive phase, the flare shows quasi-periodic pulsations (QPPs) in EUV, hard X-ray, and radio wavelengths. The periods of QPPs range from 18 s to 113 s, indicating that flare energy is released and nonthermal electrons are accelerated intermittently with multiple time scales. The interaction between the EUV wave and low-lying adjacent coronal loops (ACLs) results in contraction, expansion, and transverse vertical oscillation of ACLs. The speed of contraction in 171, 193, and 211 Å is higher than that in 304 Å. The periods of oscillation are 253 s and 275 s in 304 Å and 171 Å, respectively. A new scenario is proposed to explain the interaction. The equation that interprets the contraction and oscillation of the overlying coronal loops above a flare core can also interpret the expansion and oscillation of ACLs, suggesting that the two phenomena are the same in essence.
Authors: Qingmin Zhang, Chuan Li, Dong Li, Ye Qiu, Yanjie Zhang, and Yiwei Ni
Projects: SDO-AIA
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Publication Status: Accepted for publication in ApJL
Last Modified: 2022-09-04 22:17
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Statistical analysis of circular-ribbon flares |
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Qingmin Zhang Submitted: 2022-03-24 20:49
Circular-ribbon flares (CFs) are a special type of solar flares owing to their particular magnetic topology. In this paper, we conducted a comprehensive statistical analysis of 134 CFs from 2011 September to 2017 June, including four B-class, 82 C-class, 40 M-class, and eight X-class flares, respectively. The flares were observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. The physical properties of CFs are derived, including the location, area (ACF), equivalent radius (rCF) assuming a semi-spherical fan dome, lifetime (τCF), and peak SXR flux in 1-8 Å. It is found that all CFs are located in active regions, with the latitudes between -30\degr and 30\degr. The distributions of areas and lifetimes could be fitted with a log-normal function. There is a positive correlation between the lifetime and area. The peak SXR flux in 1-8 Å is well in accord with a power-law distribution with an index of -1.42. For the 134 CFs, 57% of them are accompanied by remote brightenings or ribbons. A positive correlation exists between the total length (LRB) and average distance (DRB) of remote brightenings. About 47% and 51% of the 134 CFs are related to type III radio bursts and jets, respectively. The association rates are independent of flare energies. About 38% of CFs are related to mini-filament eruptions, and the association rates increase with flare classes. Only 28% of CFs are related to CMEs, meaning that a majority of them are confined rather than eruptive events.
There is a positive correlation between the CME speed and peak SXR flux in 1-8 Å, and faster CMEs tend to be wider.
Authors: Yanjie Zhang, Qingmin Zhang, Dechao Song, Shuting Li, Jun Dai, Zhe Xu, and Haisheng Ji
Projects: SDO-AIA
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Publication Status: Accepted for publication in The Astrophysical Journal Supplementary Series
Last Modified: 2022-03-27 18:56
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Transverse Coronal-Loop Oscillations Induced by the Non-radial Eruption of a Magnetic Flux Rope |
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Qingmin Zhang Submitted: 2022-01-19 21:21
We investigate the transverse coronal-loop oscillations induced by the eruption of a prominence-carrying flux rope on 7 December 2012. The flux rope originating from NOAA Active Region (AR) 11621 was observed in EUV wavelengths by SDO/AIA and in Hα line center by the ground-based telescope at BBSO. The early evolution of the flux rope is divided into two steps: a slow rise phase at a speed of ≈230 km s-1 and a fast rise phase at a speed of ≈706 km s-1. The eruption generates a C5.8 flare and the onset of the fast rise is consistent with the HXR peak time of the flare. The embedded prominence has a lower speed of ≈452 km s-1. The eruption is significantly inclined from the local solar normal by ≈60 degree, suggesting a typical non-radial eruption. During the early eruption of the flux rope, the nearby coronal loops are disturbed and experience independent kink-mode oscillations in the horizontal and vertical directions. The oscillation in the horizontal direction has an initial amplitude of ≈3.1 Mm, a period of ≈294 seconds, and a damping time of ≈645 seconds. It is most striking in 171Å and lasts for three to four cycles. The oscillations in the vertical directions are observed mainly in 171, 193, and 211Å. The initial amplitudes lie in the range of 3.4-5.2 Mm, with an average value of 4.5 Mm. The periods are between 407 seconds and 441 seconds, with an average value of 423 seconds. The oscillations are damping and last for nearly four cycles. The damping times lie in the range of 570-1012 seconds, with an average value of 741 seconds. Assuming a semi-circular shape of the vertically oscillating loops, we calculate the loop lengths according to their heights. Using the observed periods, we carry out coronal seismology and estimate the internal Alfvén speeds (988-1145 km s-1) and the magnetic-field strengths (12-43 G) of the oscillating loops.
Authors: Q. M. Zhang, J. L. Chen, S. T. Li, L. Lu, and D. Li
Projects: SDO-AIA
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Publication Status: Accepted for publication in Solar Physics
Last Modified: 2022-01-24 22:17
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Energy partition in a confined flare with an extreme-ultraviolet late phase |
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Qingmin Zhang Submitted: 2021-04-08 19:48
In this paper, we reanalyze the M1.2 confined flare with a large extreme-ultraviolet (EUV) late phase on 2011 September 9, focusing on its energy partition. The radiation (~5.4x1030 erg) in 1-70 Å is nearly eleven times larger than the radiation in 70-370 Å, and is nearly 180 times larger than the radiation in 1-8 Å. The peak thermal energy of the post-flare loops is estimated to be (1.7-1.8)x1030 erg based on a simplified schematic cartoon. Based on previous results of Enthalpy-Based Thermal Evolution of Loops (EBTEL) simulation, the energy inputs in the main flaring loops and late-phase loops are (1.5-3.8)x1029 erg and 7.7x1029 erg, respectively. The nonthermal energy ((1.7-2.2)x1030 erg) of the flare-accelerated electrons is comparable to the peak thermal energy and is sufficient to provide the energy input of the main flaring loops and late-phase loops. The magnetic free energy (9.1x1031 erg) before flare is large enough to provide the heating requirement and radiation, indicating that the magnetic free energy is adequate to power the flare.
Authors: Q. M. Zhang, J. X. Cheng, Y. Dai, K. V. Tam, and A. A. Xu
Projects: GOES X-rays
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Publication Status: Accepted for publication in A&A
Last Modified: 2021-04-09 12:10
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Transverse coronal loop oscillations excited by homologous circular-ribbon flares |
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Qingmin Zhang Submitted: 2020-05-05 19:33
We report our multiwavelength observations of two homologous circular-ribbon flares (CRFs) in active region 11991 on 2014 March 5, focusing on the transverse oscillations of an extreme-ultraviolet (EUV) loop excited by the flares. The transverse oscillations are of fast standing kink-mode. The first-stage oscillation triggered by the C2.8 flare is decayless with lower amplitudes (310-510 km).
The periods (115-118 s) in different wavelengths are nearly the same, indicating coherent oscillations. The magnetic field of the loop is estimated to be 65-78 G. The second-stage oscillation triggered by the M1.0 flare is decaying with larger amplitudes (1250-1280 km). The periods decreases from 117 s in 211 {AA} to 70 s in 171 {AA}, implying a decrease of loop length or an implosion after a gradual expansion. The damping time, being 147-315 s, increases with the period, so that the values of au/P are close to each other in different wavelengths. The thickness of the inhomogeneous layer is estimated to be sim0farcs45 under the assumption of resonant absorption. This is the first observation of the excitation of two kink-mode loop oscillations by two sympathetic flares. The results are important for understanding of the excitation of kink oscillations of coronal loops and hence the energy balance in the solar corona. Our findings also validate the prevalence of significantly amplified amplitudes of oscillations by successive drivers.
Authors: Q. M. Zhang, J. Dai, Z. Xu, D. Li, L. Lu, K. V. Tam, A. A. Xu
Projects: New Vacuum Solar Telescope (NVST)
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Publication Status: accepted for publication in A&A
Last Modified: 2020-05-06 13:30
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Pre-flare coronal dimmings |
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Qingmin Zhang Submitted: 2016-11-27 18:45
Coronal dimmings are regions of decreased extreme-ultravoilet (EUV) and/or X-ray (originally Skylab, then Yohkoh/SXT) intensities,
which are often associated with flares and coronal mass ejections (CMEs). The large-scale, impulsive dimmings have substantially been
observed and investigated. The pre-flare dimmings prior to the flare impulsive phase, however, have rarely been studied in detail.
In this paper, we focus on the pre-flare coronal dimmings. We report our multiwavelength observations of the GOES X1.6 solar flare and the
accompanying halo CME produced by the eruption of a sigmoidal magnetic flux rope (MFR) in NOAA active region (AR) 12158 on 2014 September 10.
The eruption was observed by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory (SDO). The photospheric line-of-sight
magnetograms were observed by the Helioseismic and Magnetic Imager (HMI) aboard SDO. The soft X-ray (SXR) fluxes were recorded by the GOES
spacecraft. The halo CME was observed by the white light coronagraphs of the Large Angle Spectroscopic Coronagraph (LASCO) aboard SOHO.
About 96 minutes before the onset of flare/CME, narrow pre-flare coronal dimmings appeared at the two ends of the twisted MFR. They extended very
slowly with their intensities decreasing with time, while their apparent widths (8-9 Mm) nearly kept constant. During the impulsive and decay phases
of flare, typical fanlike twin dimmings appeared and expanded with much larger extent and lower intensities than the pre-flare dimmings.
The percentage of 171 Å intensity decrease reaches 40%. The pre-flare dimmings are most striking in 171, 193, and 211 Å with
formation temperatures of 0.6-2.5 MK. The northern part of the pre-flare dimmings could also be recognized in 131 and 335 Å.
To our knowledge, this is the first detailed study of pre-flare coronal dimmings, which can be explained by the density depletion as a result of the
gradual expansion of the coronal loop system surrounding the MFR during the slow rise of the MFR.
Authors: Q. M. Zhang, Y. N. Su, and H. S. Ji
Projects: SDO-AIA
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Publication Status: to be accepted for publication by A&A
Last Modified: 2016-11-30 12:19
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Chromospheric Condensation and Quasi-periodic Pulsations in a Circular-ribbon Flare |
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Qingmin Zhang Submitted: 2016-09-13 02:44
In this paper, we report our multiwavelength observations of the C3.1 circular-ribbon flare SOL2015-10-16T10:20 in active region (AR) 12434.
The flare consisted of a circular flare ribbon (CFR), an inner flare ribbon (IFR) inside, and a pair of short parallel flare ribbons (PFRs).
The PFRs located to the north of IFR were most striking in the Interface Region Imaging Spectrograph (IRIS) 1400 Å and 2796 Å images.
For the first time, we observed the circular-ribbon flare in the Ca II H line of the Solar Optical Telescope (SOT) aboard
Hinode, which has similar shape as observed in the Atmospheric Imaging Assembly (AIA) 1600 Å aboard the Solar Dynamic Observatory (SDO).
Photospheric line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) aboard SDO show that the flare was associated with positive
polarities and a negative polarity inside. The IFR and CFR were cospatial with the negative polarity
and positive polarities, implying the existence of a magnetic null point (B=0) and the dome-like spine-fan topology.
During the impulsive phase of the flare, ``two-step'' raster observations of IRIS with a cadence of 6 s and an exposure time of 2 s show plasma
downflow at the CFR in the Si IV \lambda1402.77 line (log T≈4.8), suggesting chromospheric condensation.
The downflow speeds first increased rapidly from a few km s-1 to the peak values of 45-52 km s-1, before decreasing gradually to the initial levels.
The decay timescales of condensation were 3-4 minutes, indicating ongoing magnetic reconnection. Interestingly, the downflow speeds are positively correlated
with logarithm of the Si IV line intensity and time derivative of the GOES soft X-ray (SXR) flux in 1-8 Å.
The radio dynamic spectra are characterized by a type III radio burst associated with the flare, which implies that the chromospheric condensation was most
probably driven by nonthermal electrons. Using an analytical expression and the peak Doppler velocity, we derived the lower limit of energy
flux of the precipitating electrons, i.e., 0.65x1010 erg cm-2 s-1. The Si IV line intensity and SXR derivative show quasi-periodic pulsations
with periods of 32-42 s, which are likely caused by intermittent null-point magnetic reconnections modulated by the fast wave propagating
along the fan surface loops at a phase speed of 950-1250 km s-1. Periodic accelerations and precipitations of the electrons result in periodic heating observed in the
Si IV line and SXR.
Authors: Q. M. Zhang, D. Li, and Z. J. Ning
Projects: IRIS
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Publication Status: accepted for publication in ApJ
Last Modified: 2016-09-14 12:01
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Observations of multiple blobs in homologous solar coronal jets in closed loops |
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Qingmin Zhang Submitted: 2016-01-18 20:58
Coronal bright points (CBPs) and jets are ubiquitous small-scale brightenings that are often associated with each other. In this paper, we report our
multiwavelength observations of two groups of homologous jets. The first group was observed by the Extreme-Ultraviolet Imager (EUVI) aboard
the behind Solar TErrestrial RElations Observatory (STEREO) spacecraft in 171 Å and 304 Å on 2014 September 10, from a location where
data from the Solar Dynamic Observatory (SDO) could not observe. The jets (J1-J6) recurred for six times with
intervals of 5-15 minutes. They originated from the same primary CBP (BP1) and propagated in the northeast direction along large-scale, closed coronal loops.
Two of the jets (J3 and J6) produced sympathetic CBPs (BP2 and BP3) after reaching the remote footpoints
of the loops. The time delays between the peak times of BP1 and BP2 (BP3) are 240±75 s (300±75 s). The jets were not coherent. Instead,
they were composed of bright and
compact blobs. The sizes and apparent velocities of the blobs are 4.5-9 Mm and 140-380 km s-1, respectively.
The arrival times of the multiple blobs in the jets at the far-end of the loops indicate that the sympathetic CBPs are caused by jet flows
rather than thermal conduction fronts. The second group was observed by the Atmospheric Imaging Assembly aboard SDO in various
wavelengths on 2010 August 3. Similar to the first group, the jets originated from a short-lived bright point (BP) at the boundary of active region 11092
and propagated along a small-scale, closed loop before flowing into the active region. Several tiny blobs with sizes of ~1.7 Mm and apparent velocity
of ~238 km s-1 were identified in the jets. We carried out the differential emission measure (DEM) inversions to investigate the temperatures of
the blobs, finding that the blobs were multithermal with average temperature of 1.8-3.1 MK. The estimated number densities of the blobs were
(1.7-2.8)x109 cm-3.
Authors: Q. M. Zhang, H. S. Ji, and Y. N. Su
Projects: SDO-AIA
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Publication Status: accepted for publication in Solar Physics
Last Modified: 2016-01-20 12:25
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Multiwavelength observations of a partially eruptive filament on 2011 September 8 |
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Qingmin Zhang Submitted: 2015-03-10 19:25
In this paper, we report our multiwavelength observations of a partial filament eruption event in NOAA
active region 11283 on 2011 September 8. A magnetic null point and the corresponding spine and
separatrix surface are found in the active region. Beneath the null point, a sheared
arcade supports the filament along the highly complex and fragmented polarity inversion line. After
being activated, the sigmoidal filament erupted and
split into two parts. The major part rose at the speeds of 90-150 km s-1 before
reaching the maximum apparent height of ~115 Mm. Afterwards, it returned to the solar surface
in a bumpy way at the speeds of 20-80 km s-1. The rising and falling motions were clearly
observed in the extreme-ultravoilet (EUV), UV, and Hα wavelengths. The failed eruption
of the main part was associated with an M6.7 flare with a single hard X-ray source. The
runaway part of the filament, however, separated from and rotated around the major part for ~1
turn at the eastern leg before escaping from the corona,
probably along large-scale open magnetic field lines. The ejection of the runaway part resulted in
a very faint coronal mass ejection (CME) that propagated at an apparent speed of 214 km s-1
in the outer corona.
The filament eruption also triggered transverse kink-mode oscillation of the adjacent coronal loops in
the same AR. The amplitude and period of the oscillation were 1.6 Mm and 225 s.
Our results are important for understanding the mechanisms of partial filament eruptions
and provide new constraints to theoretical models. The multiwavelength observations also shed
light on space weather prediction.
Authors: Q. M. Zhang, Z. J. Ning, Y. Guo, T. H. Zhou, X. Cheng, H. S. Ji, L. Feng, T. Wiegelmann
Projects: SDO-AIA
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Publication Status: Accepted for publication in ApJ
Last Modified: 2015-03-11 14:47
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Reciprocatory magnetic reconnection in a coronal bright point |
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Qingmin Zhang Submitted: 2014-06-22 20:21
Coronal bright points (CBPs) are small-scale and long-duration brightenings
in the lower solar corona. They are often explained in terms of magnetic
reconnection. We aim to study the sub-structures of a CBP and clarify the relationship among the brightenings of different patches inside the CBP.
The event was observed by the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 22-23. The CBP showed repetitive brightenings (or CBP flashes). During each of the two successive CBP flashes, i.e., weak and strong flashes which are separated by ~2 hr, the XRT images revealed that the CBP was composed of two chambers, i.e., patches A and B. During the weak flash, patch A brightened first, and patch B brightened ~2 min later. During the transition, the right leg of a large-scale coronal loop drifted from the right side of the CBP to the left side. During the strong flash, patch B brightened first, and patch A brightened ~2 min later. During the transition, the right leg of the large-scale coronal loop drifted from the left side of the CBP to the right side. In each flash, the rapid change of the connectivity of the large-scale coronal loop is strongly suggestive of the interchange reconnection. For the first time we found reciprocatory reconnection in the CBP, i.e., reconnected loops in the outflow region of the first reconnection process serve as the inflow of the second reconnection process.
Authors: Q. M. Zhang, P. F. Chen, M. D. Ding, and H. S. Ji
Projects: None
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Publication Status: Accepted for publication in A&A
Last Modified: 2014-06-23 12:07
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Blobs in recurring EUV jets |
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Qingmin Zhang Submitted: 2014-05-20 19:44
Coronal jets are one type of ubiquitous small-scale activities caused by
magnetic reconnection in the solar corona. They are often associated with
cool surges in the chromosphere.
In this paper, we report our discovery of blobs in the recurrent
and homologous jets that occurred at the western edge of NOAA active
region 11259 on 2011 July 22.
The jets were observed in the seven extreme-ultraviolet (EUV)
filters of the Atmospheric Imaging Assembly (AIA) instrument
aboard the Solar Dynamics Observatory (SDO). Using the base-difference
images of the six filters (94, 131, 171, 211, 193, and 335 Å), we
carried out the differential emission measure (DEM) analyses to explore
the thermodynamic evolutions of the jets. The jets were
accompanied by cool surges observed in the Hα line center of
the ground-based telescope in the Big Bear Solar Observatory.
The jets that had lifetimes of 20-30 min recurred at the same place
for three times with interval of 40-45 min. Interestingly,
each of the jets intermittently experienced several upward eruptions at the
speed of 120-450 km s-1. After reaching the maximum heights,
they returned back to the solar surface, showing near-parabolic trajectories.
The falling phases were more evident in the low-T filters than in
the high-T filters, indicating that the jets experienced cooling after the
onset of eruptions. We identified bright and compact blobs in the
jets during their rising phases. The simultaneous
presences of blobs in all the EUV filters were consistent with the broad
ranges of the DEM profiles of the blobs (5.5≤ log T≤7.5), indicating
their multi-thermal nature. The median temperatures of the blobs were
~2.3 MK. The blobs that were ~3 Mm in diameter had lifetimes
of 24-60 s.
To our knowledge, this is the first report of blobs in coronal jets. We
propose that these blobs are plasmoids created by the magnetic reconnection
as a result of tearing-mode instability and ejected out along the jets.
Authors: Q. M. Zhang and H. S. Ji
Projects: None
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Publication Status: accepted for publication in A&A
Last Modified: 2014-05-21 13:36
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Chromospheric evaporation in sympathetic coronal bright points |
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Qingmin Zhang Submitted: 2013-07-29 19:16
{Chromospheric evaporation is a key process in solar
flares that has extensively been investigated using the spectroscopic
observations. However, direct soft X-ray (SXR) imaging of the process
is rare, especially in remote brightenings associated with the primary
flares that have recently attracted dramatic attention.}
{We intend to find the evidence for chromospheric evaporation
and figure out the cause of the process in sympathetic coronal bright
points (CBPs), i.e., remote brightenings induced by the primary CBP.}
{We utilise the high-cadence and high-resolution SXR
observations of CBPs from the X-ray Telescope
(XRT) aboard the Hinode spacecraft on 2009 August 23.}
{We discover thermal conduction front propagating from the
primary CBP, i.e., BP1, to one of the sympathetic CBPs, i.e., BP2 that is
60arcsec away from BP1. The apparent velocity of the thermal conduction
is sim138 km s-1. Afterwards, hot plasma flowed upwards into the
loop connecting BP1 and BP2 at a speed of sim76 km s-1, a clear
signature of chromospheric evaporation. Similar upflow was also observed
in the loop connecting BP1 and the other sympathetic CBP, i.e.,
BP3 that is 80arcsec away from BP1, though
less significant than BP2. The apparent velocity of the upflow is sim47
km s-1. The thermal conduction front propagating from BP1 to BP3
was not well identified except for the jet-like motion also originating from BP1.}
{We propose that the gentle chromospheric evaporation in the
sympathetic CBPs were caused by thermal conduction originating from
the primary CBP.}
Authors: Q. M. Zhang and H. S. Ji
Projects: None
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Publication Status: accepted by A&A Letters
Last Modified: 2013-07-30 13:35
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Observation and Simulation of Longitudinal Oscillations of an Active Region Prominence |
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Qingmin Zhang Submitted: 2012-04-17 08:35
{Filament longitudinal oscillations have been observed on the solar disk
in Hα .}
{We intend to find an example of the longitudinal oscillations of a
prominence, where the magnetic dip can be seen directly,
and examine what is the restoring force of such kind of oscillations.}
{We carry out a multiwavelength data analysis of the active region
prominence oscillations above the western limb on 2007
February 8. Besides, we perform a one-dimensional hydrodynamic
simulation of the longitudinal oscillations.}
{The high-resolution observations by Hinode/SOT indicate that the
prominence, seen as a concave-inward shape in lower-resolution Extreme
Ultraviolet (EUV) images, actually consists of many concave-outward
threads, which is indicative of the existence of magnetic dips. After
being injected into the dip region, a bulk of prominence material started
to oscillate for more than 3.5 hours, with the period being 52 min. The
oscillation decayed with time, with the decay timescale being 133 min.
Our hydrodynamic simulation can well reproduce the oscillation period, but
the damping timescale in the simulation is 1.5 times as long as the
observations.}
{The results clearly show the prominence longitudinal oscillations around
the dip of the prominence and our study suggests that the restoring force
of the longitudinal oscillations might be the gravity. Radiation and heat
conduction are insufficient to explain the decay of the oscillations. Other
mechanisms, such as wave leakage and mass accretion, have to be
considered. The possible relation between the longitudinal oscillations
and the later eruption of a prominence thread, as well as a coronal mass
ejection (CME), is also discussed.}
Authors: Qingmin Zhang, Pengfei Chen, Chun Xia, Rony Keppens
Projects: Hinode/SOT
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Publication Status: accepted
Last Modified: 2012-04-17 13:55
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