Numerical Experiments on Fine Structure Within Reconnecting Current Sheets in Solar Flares

Shen, Chengcai; Lin, Jin‐Ming; Murphy, N. A.

doi:10.1088/0004-637x/737/1/14

Cited by 123 publications

(171 citation statements)

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“…They concluded that the difference in velocities of plasma blobs could be ascribed to the reconnection processes occurring in the different environments. Similar phenomenon was also observed in numerical experiments on the reconnection process taking place in two-ribbon flares (see also Forbes and Malherbe 1991;Riley et al 2007;Shen et al 2011).…”

Section: Upward Reconnection Outflowssupporting

confidence: 82%

“…Panels in Fig. 12 display LASCO C2 images of the same process that had been enhanced by the wavelet technique, which further indicates that discriminating a post-CME CS from a streamer CS is not difficult, although in both cases the tearing mode instability could take place in the same fashion (e.g., see also Einaudi et al 2001) since the occurrence of the tearing mode depends on the length to thickness ratio of the CS (e.g., see Furth et al 1963;Loureiro et al 2007;Ni et al 2010;Shen et al 2011;Bárta et al 2011aBárta et al , 2011bMei et al 2012) no matter whether the CS is stretched by the expanding solar wind, or by the disrupting coronal magnetic field.…”

Section: Upward Reconnection Outflowsmentioning

confidence: 96%

“…We need to note here that S. Savage (2014, private communications) keeps pointing out that SADs and plasmoids usually appearing in numerical experiments (e.g., see Bhattacharjee et al 2009;Bárta et al 2011a;Shen et al 2011;Mei et al 2012; and references therein) are not the same thing. SADs are low-density regions, while plasmoids show up in simulations as high density structures, and plasmoids appear when we view CSs edge-on, while SADs appear when we view CSs face-on.…”

Section: Downward Reconnection Outflowsmentioning

confidence: 97%

“…Compared with the anti-sunward flow, the sunward flow is apparently slow. 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%

“…Since the resistivity is small and the catastrophe takes place much faster than the dissipation at the beginning of the eruption (see discussions of Lin and Forbes 2000;Lin 2002), the CS is able to develop to a large scale, and various plasma instabilities would occur in the CS. Linear theory of the tearing mode instability indicates that the CS becomes unstable as its length exceeds 2π times its thickness (Furth et al 1963;Priest and Forbes 2000), and nonlinear investigations through numerical experiments suggest that this ratio could apparently exceed 10 and even up to 100, before the tearing mode is invoked (e.g., see Loureiro et al 2007;Ni et al 2010;Shen et al 2011;Bárta et al 2011aBárta et al , 2011bMei et al 2012). Plasma instabilities yield turbulence inside the CS that may significantly enhance the dissipation of the magnetic field, resulting in an effective resistivity that is much higher than the traditional Spitzer value (Strauss 1986(Strauss , 1988Ambrosiano et al 1988;Bhattacharjee and Yuan 1995;Shibata and Tanuma 2001;Skender and Lapenta 2010;Bárta et al 2011aBárta et al , 2011bShen et al 2011;Mei et al 2012; and references therein).…”

Section: Introductionmentioning

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: Upward Reconnection Outflowssupporting

confidence: 82%