Simultaneous Observation of Reconnection Inflow and Outflow Associated With the 2010 August 18 Solar Flare

Takasao, Shinsuke; Asai, Ayumi; Isobe, Hiroaki; Shibata, Kazunari

doi:10.1088/2041-8205/745/1/l6

Cited by 187 publications

(198 citation statements)

References 47 publications

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“…Ignoring the projection effect and assuming the outflow speed to be identified with the local Alfvén speed, Su et al (2013) eventually ended up with that M A is between 0.05 and 0.5. These results are similar to those obtained by Takasao et al (2012) who noticed that the inflow speed was between 12 and 90 km s −1 , the outflow speed between 220 and 460 km s −1 , and M A between 0.055 and 0.2 accordingly.…”

Section: The Reconnection Inflow Near the Current Sheetsupporting

confidence: 91%

“…Shen et al (2011) pointed out that this is generally true because the sunward flow is always slowed down by its interaction with the closed flare loops below. Studying the SDO/AIA data, Takasao et al (2012) brought the speed of the anti-sunward flow to the range from 220 to 460 km s −1 , and that of the sunward flow to the range from 250 to 280 km s −1 .…”

Section: Downward Reconnection Outflowsmentioning

confidence: 99%

“…Similar plasma flows due to reconnection in the eruption were continuously observed later. Takasao et al (2012) reported observations and studies of a C4.2 flare occurring on 2010 August 18 on the northwest limb. Flare loops developed in this event could be seen in both hot (> 7 × 10 6 K) and cool (4 × 10 5 K) temperature spectral lines, and a sheet structure could be recognized to extend from the top of flare loops to the outermost corona, and bi-directional plasma flows were identified in both low and high temperatures images, which suggested the wide range of the plasma temperature inside the sheet as observed in previous events (e.g., see McKenzie and Hudson 1999;Innes et al 2003a;Asai et al 2004).…”

Section: Bi-directional Reconnection Outflows Observed In a Single Eventmentioning

confidence: 99%

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Review on Current Sheets in CME Development: Theories and Observations

et al. 2015

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We introduce how the catastrophe model for solar eruptions predicted the formation and development of the long current sheet (CS) and how the observations were used to recognize the CS at the place where the CS is presumably located. Then, we discuss the direct measurement of the CS region thickness by studying the brightness distribution of the CS region at different wavelengths. The thickness ranges from 10 4 km to about 10 5 km at heights between 0.27 and 1.16 R from the solar surface. But the traditional theory indicates that the CS is as thin as the proton Larmor radius, which is of order tens of meters in the corona. We look into the huge difference in the thickness between observations and theoretical expectations. The possible impacts that affect measurements and results are studied, and physical causes leading to a thick CS region in which reconnection can still occur at a reasonably fast rate are analyzed. Studies in both theories and observations suggest that the difference between the true value and the apparent value of the CS thickness is not significant as long as the CS could be recognised in observations. We review observations that show complex structures and flows inside the CS region and present recent numerical modelling results on some aspects of these structures. Both observations and numerical experiments indicate that the downward reconnection outflows are usually slower than the upward ones in the same eruptive event. Numerical simulations show that the complex structure inside CS and its temporal behavior as a result of turbulence and the Petschek-type slow-mode shock could probably account for the thick CS and fast reconnection. But whether the CS itself is that thick still remains unknown since, for the time being, we cannot measure the electric current directly in that region. We also review the most recent laboratory experiments of reconnection driven by energetic laser beams, and discuss some important topics for future works.

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Section: The Reconnection Inflow Near the Current Sheetsupporting

confidence: 91%

Section: Downward Reconnection Outflowsmentioning

confidence: 99%

Section: Bi-directional Reconnection Outflows Observed In a Single Eventmentioning

confidence: 99%

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Review on Current Sheets in CME Development: Theories and Observations

et al. 2015

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“…Most of the blobs have lifetime of 24−60 s before merging with the background plasma and disappearing. Such intermittent magnetic plasmoids or blobs created by magnetic reconnection have also been observed in the large-scale current sheet (CS) driven by CMEs and the smallscale CS associated with chromospheric jets (Asai et al, 2004;Lin et al, 2005;Takasao et al, 2012;Singh et al, 2012;Kumar & Cho, 2013;Lin et al, 2015). They are generally explained by the tearing-mode instability (TMI) of the thin CS where a series of magnetic islands are recurrently created during magnetic reconnection (Furth et al, 1963;Drake et al, 2006;Bárta et al, 2008;Innes et al, 2015), which makes electron acceleration more efficient and dynamic (Kliem et al, 2000).…”

Section: Introductionmentioning

confidence: 96%

Observations of Multiple Blobs in Homologous Solar Coronal Jets in Closed Loop

Zhang

2016

Sol Phys

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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 171Å and 304Å 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)×10 9 cm −3 .

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“…Considerable pieces of evidence for features likely linked to reconnection in solar flares 7,8 and coronal mass ejections (CMEs 9 ) have been obtained so far. These include signatures of plasma inflow/outflow [10][11][12][13][14] , hot cusp structures 15 , current sheets [16][17][18] , fast-mode standing shocks 19 , and plasmoid ejection 20 .…”

mentioning

confidence: 99%

Imaging coronal magnetic-field reconnection in a solar flare

et al. 2013

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Abstract:Magnetic field reconnection is believed to play a fundamental role in magnetized plasma systems throughout the universe 1 , including planetary magnetospheres, magnetars, and accretion discs around black holes. This letter presents extreme ultraviolet (EUV) and X-ray observations of a solar flare showing magnetic reconnection with a level of clarity not previously achieved. The multi-wavelength EUV observations from SDO/AIA show inflowing cool loops and newly formed, outflowing hot loops, as predicted. RHESSI X-ray spectra and images simultaneously show the appearance of plasma heated to >10 MK at the expected locations. These two data sets provide solid visual evidence of magnetic reconnection producing a solar flare, validating the basic physical mechanism of popular flare models. However, new features are also observed that need to be included in reconnection and flare studies, such as 3D non-uniform, non-steady, and asymmetric evolution. Main Text:The early concept of magnetic reconnection was proposed in the 1940s 1 to explain energy release in solar flares, the most powerful explosive phenomena in the solar system. The reconnection process reconfigures the field topology and converts magnetic energy to thermal energy, mass motions, and particle acceleration. The theories and related numerical simulations, especially 3D modelling, are still subjects of extensive research to obtain a full understanding of the process under different conditions. Meanwhile, observational studies have made progress in finding evidence of reconnection and deriving its physical properties to constrain and improve the theories.In-situ measurements of the magnetic field, plasma parameters, and particle distributions have shown the existence of magnetic reconnection in laboratory plasmas 2, 3 , fusion facilities, and magnetospheres of planets 4,5 . Such in-situ measurements are still not possible in the extremely hot solar atmosphere. Instead, observations are obtained through remote sensing of emissions across the entire electromagnetic spectrum from radio to X rays and gamma rays.However, in the corona 6 the magnetic field pressure dominates the plasma pressure (low plasma beta) and the magnetic flux is "frozen into" the highly conductive plasma. As a result, the emitting plasma trapped in coronal loops outlines the geometry of the magnetic field and their structural changes reflect the changes of the field connectivity (in general). Considerable pieces of evidence for features likely linked to reconnection in solar flares 7,8 and coronal mass ejections (CMEs 9 ) have been obtained so far. These include signatures of plasma inflow/outflow 10-14 , hot cusp structures 15 , current sheets [16][17][18] , fast-mode standing shocks 19 , and plasmoid ejection 20 .However, most evidence has been indirect and fragmented. Detailed observations of the complete picture are still missing due to the highly dynamic flare/CME process and limited observational capabilities.The launch of the Solar Dynamic Observatory (SDO 21 ) in 2010 sign...

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Simultaneous Observation of Reconnection Inflow and Outflow Associated With the 2010 August 18 Solar Flare

Cited by 187 publications

References 47 publications

Review on Current Sheets in CME Development: Theories and Observations

Review on Current Sheets in CME Development: Theories and Observations

Observations of Multiple Blobs in Homologous Solar Coronal Jets in Closed Loop

Imaging coronal magnetic-field reconnection in a solar flare

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