Effects of the Length-width Ratio of Current Sheet on Asymmetry Multiple X-line Reconnection
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摘要: 采用可压缩电阻性磁流体力学模型，研究了初始电流片的长宽比
${L_x}$ 对非对称多重X线磁场重联的影响。研究结果发现，当${L_x}$ 超过一定的阈值时，非对称磁场重联的演化过程中将伴有多重X线重联发生。进一步地研究结果表明，当${L_x}$ 越大，多重X线重联就越容易出现，相同时间间隔内所诱发的次级磁岛的尺寸也随之相应变大，不仅如此，次级磁岛的尺寸占整个模拟尺寸的比例也有所增大。对于${L_x}$ 比较大的情形，当非对称多重X线磁场重联发展到一定程度后，非对称多重X线磁场重联的重联点基本不随时间变化，并且所诱发的大尺度次级磁岛的大小也基本稳定，该结论与Magnetospheric Multiscale （MMS） 观测现象一致。因此这些结果可以用来解释一些卫星观测现象，尤其对空间物理中有关次级磁重联产生的多重X重联的观测有一定指导作用。Abstract: Effects of the length-width ratio of current sheet (${L_x}$ ) on asymmetry multiple X-line reconnection are investigated using a two-dimensional compressible resistive Magnetohydrodynamics (MHD) model. It is found that multiple-X lines induced by secondary tearing instability occur during the asymmetry reconnection processes when${L_x}$ exceeds a critical value. Multiple X-line reconnection occurs faster as${L_x}$ becomes larger, and percent of secondary island is also increases. For large${L_x}$ cases, locations of the reconnection points of asymmetry multiple X-line reconnection and sizes of the secondary island are tend to stationary with the evolution of the multiple X-line reconnection, which is consistent to the Magnetospheric Multiscale (MMS) observations. The results here can be useful for understanding some observed data, even for the secondary tearing instability and multipleX-line reconnection observations.-
Key words:
- Magnetic reconnection /
- Magnetohydrodynamics /
- Secondary island /
- Current sheet
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图 1
$ {L_x} = 24 $ 和$ {L_x} = 30 $ 时不同时刻的电流$ {J_y} $ 分布Figure 1. Contour of
${J_y}$ with$ {L_x} = 24 $ and$ {L_x} = 30 $ 
图 2 不同
$ {L_x} $ 条件下$t = 160$ 时电流$ {J_y} $ 的分布Figure 2. Contour of
${J_y}$ for$t = 160$ with different$ {L_x} $ 
图 3 不同
$ {L_x} $ 条件下$t = 300$ 和$t = 600$ 时电流$ {J_y} $ 的分布Figure 3. Contour of
${J_y}$ for$t = 300$ and$t = 600$ with different$ {L_x} $ 
图 4 不同
$ {L_x} $ 下多重X重联发生后$t = 600$ 时次级磁岛大小所占系统的比例Figure 4. Percent of secondary island at
$t = 600$ for different$ {L_x} $ 
图 5
$ {L_x} = 40 $ 时不同时刻电流$ {J_y} $ 的分布Figure 5. Distribution of
${J_y}$ of$ {L_x} = 40 $ for different times
图 6
$ {L_x} = 40 $ 时$t = 300$ 到$t = 600$ 一侧重联点位置的分布（红色为$t = 550$ 到$t = 600$ 时刻）Figure 6. Location of reconnection point for
$ {L_x} = 40 $ from$t = 300$ to$t = 600$ (red for$t = 550$ to$t = 600$ )表 1 不同
$ {L_x} $ 条件下多重X重联的发生情况Table 1. Occurrence of multiple-X lines reconnection with different
$ {{\boldsymbol{L}}_{\boldsymbol{x}}} $ Lx 24 25 26 28 30 32 40 是否发生多重X重联 否 否 是 是 是 是 是 
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[1] GIOVANELLI R G. A theory of chromospheric flares[J]. Nature, 1946, 158(4003): 81-82 doi: 10.1038/158081a0 [2] PRIEST E R. The magnetohydrodynamics of current sheets[J]. Reports on Progress in Physics, 1985, 48(7): 955-1090 doi: 10.1088/0034-4885/48/7/002 [3] GOSLING J T, THOMSEN M F, BAME S J, et al. Cold ion beams in the low latitude boundary layer during accelerated flow events[J]. Geophysical Research Letters, 1990, 17(12): 2245-2248 doi: 10.1029/GL017i012p02245 [4] KU H C, SIBECK D G. Internal structure of flux transfer events produced by the onset of merging at a single X line[J]. Journal of Geophysical Research: Space Physics, 1997, 102(A2): 2243-2260 doi: 10.1029/96JA03162 [5] CASSAK P A, SHAY M A. Structure of the dissipation region in fluid simulations of asymmetric magnetic reconnection[J]. Physics of Plasmas, 2009, 16(5): 055704 doi: 10.1063/1.3086867 [6] WANG R S, NAKAMURA R, LU Q M, et al. Asymmetry in the current sheet and secondary magnetic flux ropes during guide field magnetic reconnection[J]. Journal of Geophysical Research: Space Physics, 2012, 117(A7): A07223 [7] LIU Z Q, LU J Y, WANG C, et al. A three-dimensional high Mach number asymmetric magnetopause model from global MHD simulation[J]. Journal of Geophysical Research: Space Physics, 2015, 120(7): 5645-5666 doi: 10.1002/2014JA020961 [8] DOSS C E, KOMAR C M, CASSAK P A, et al. Asymmetric magnetic reconnection with a flow shear and applications to the magnetopause[J]. Journal of Geophysical Research: Space Physics, 2015, 120(9): 7748-7763 doi: 10.1002/2015JA021489 [9] BOROVSKY J E, HESSE M. The reconnection of magnetic fields between plasmas with different densities: scaling relations[J]. Physics of Plasmas, 2007, 14(10): 102309 doi: 10.1063/1.2772619 [10] CASSAK P A, SHAY M A. Scaling of asymmetric magnetic reconnection: General theory and collisional simulations[J]. Physics of Plasmas, 2007, 14(10): 102114 doi: 10.1063/1.2795630 [11] BIRN J, BOROVSKY J E, HESSE M, et al. Scaling of asymmetric reconnection in compressible plasmas[J]. Physics of Plasmas, 2010, 17(5): 052108 doi: 10.1063/1.3429676 [12] WANG L, WANG X G, WANG X Q, et al. Asymmetric magnetic reconnection with out-of-plane shear flows in a two dimensional hybrid model[J]. Physics of Plasmas, 2015, 22(5): 052110 doi: 10.1063/1.4919965 [13] TRATTNER K J, MULCOCK J S, PETRINEC S M, et al. Location of the reconnection line at the magnetopause during southward IMF conditions[J]. Geophysical Research Letters, 2007, 34(3): L03108 [14] VINES S K, FUSELIER S A, PETRINEC S M, et al. Occurrence frequency and location of magnetic islands at the dayside magnetopause[J]. Journal of Geophysical Research: Space Physics, 2017, 122(4): 4138-4155 doi: 10.1002/2016JA023524 [15] FUSELIER S A, PETRINEC S M, TRATTNER K J, et al. Observational evidence of large-scale multiple reconnection at the Earth’s dayside magnetopause[J]. Journal of Geophysical Research: Space Physics, 2018, 123(10): 8407-8421 doi: 10.1029/2018JA025681 [16] LEE L C, FU Z F. Multiple X line reconnection: 1. A criterion for the transition from a single X line to a multiple X line reconnection[J]. Journal of Geophysical Research: Space Physics, 1986, 91(A6): 6807-6815 doi: 10.1029/JA091iA06p06807 [17] MA Z W, WANG L C, LI L J. Reconnection dynamics with secondary tearing instability in compressible Hall plasmas[J]. Physics of Plasmas, 2015, 22(6): 062104 doi: 10.1063/1.4922057 [18] DAI L. Structures of Hall fields in asymmetric magnetic reconnection[J]. Journal of Geophysical Research: Space Physics, 2018, 123(9): 7332-7341 doi: 10.1029/2018JA025251 [19] LI L J, ZHANG X, WANG L C, et al. Slow shock formation and structure with sub-Alfvénic shear flow in magnetic reconnection[J]. Journal of Geophysical Research: Space Physics, 2012, 117(A6): A06207 [20] ZHANG X, LI L J, WANG L C, et al. Influences of sub-Alfvénic shear flows on nonlinear evolution of magnetic reconnection in compressible plasmas[J]. Physics of Plasmas, 2011, 18(9): 092112 doi: 10.1063/1.3643792 [21] MA Z W, BHATTACHARJEE A. Hall magnetohydrodynamic reconnection: the Geospace environment modeling challenge[J]. Journal of Geophysical Research: Space Physics, 2001, 106(A3): 3773-3782 doi: 10.1029/1999JA001004 -
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