导向磁场对非对称多重X线重联演化过程的影响

doi:10.19596/j.cnki.1001-246x.8627

摘要/Abstract

摘要：

采用二维可压缩电阻性磁流体力学模型, 研究导向磁场(B_y0)对非对称多重X线磁场重联过程的影响。研究发现: 对于未加B_y0时有多重X线重联发生的情形, 加入B_y0之后, 会加快次级磁岛的出现。当B_y0增加到一定程度后, 该促进效应有所减弱。而对于未加B_y0时无多重X线重联发生的情形, 加入一定大小的B_y0之后, 会诱发次级磁岛的产生, 即诱发了非对称多重X线重联。进一步研究发现, 当B_y0增加到一定程度后, 将无法诱发非对称多重X线重联。两种情形均表明, B_y0的加入可以促进或者诱发非对称多重X线重联, 且存在一个阈值, 当B_y0超过这个阈值之后, 该促进或诱发效应开始减弱。所得结果可以用于解释一些卫星观测现象, 尤其对空间物理中有关导向磁场非对称多重X线重联观测结果的理解有参考价值。

关键词: 磁重联, 导向磁场, 磁流体力学, 次级磁岛

Abstract:

Influences of guiding field on asymmetry multiple-X lines reconnection are investigated using two-dimensional compressible resistive MHD models. It is found that the external guiding field B_y0 can promote multiple-X lines reconnection occur during the asymmetry reconnection processes for the case of multiple-X lines reconnection occur without the guidance field. Multiple-X lines reconnection occurs faster as B_y0 becomes larger. For the case that there is no multiple-X lines reconnection appeared without a guiding field, the secondary magnetic island will be induced when including a certain guiding field. Further study found that multiple-X lines reconnection could not be induced when the guiding field becomes large enough. Both cases show that the guiding field can promote or induce the occurrence of the multiple-X lines reconnection, and there is a threshold value. When B_y0 exceeded the threshold value, the promoting or inducing effect becomes weak. The results here can be useful for understanding some observed data, even for the multiple-X lines reconnection observations.

Key words: magnetic reconnection, guiding field, magneto hydro dynamic, secondary island

李灵杰. 导向磁场对非对称多重X线重联演化过程的影响[J]. 计算物理, 2023, 40(4): 436-442.

Lingjie LI. Evolutions of Asymmetric Multiple-X Lines Reconnection with Influences of Guiding Field[J]. Chinese Journal of Computational Physics, 2023, 40(4): 436-442.

图/表 7

图1 当Lx=26时(a)、(b)By0=0，(c)、(d)By0=0.5，(e)、(f)By0=2.0时电流密度Jy的分布

Fig.1 Distribution of current density Jy at different time with Lx=26 for By0 (a) and (b)By0=0;(c) and (d)By0=0.5;(e) and (f)By0=2.0

图2 Lx=26时不同By0次级磁岛出现的时间

Fig.2 Onset time of secondary island for Lx=26 with By0

图3 Lx=25，t=500时(a)By0=0.5，(b)By0=1.0，(c)By0=1.5，(d)By0=2.0时电流密度Jy

Fig.3 Distribution of current density Jy for t=500 at By0 with Lx=25 (a)By0=0.5, (b)By0=1.0, (c)By0=1.5, (d)By0=2.0

表1 不同By0下多重X线重联的发生情况

Table 1 Situation of multiple-X lines reconnection with different By0

B_y0	0	0.5	1.0	1.2	1.5	1.8	2.0	2.5	3.0
多重X线重联	否	否	否	是	是	是	是	否	否

图4 Lx=25时不同By0次级磁岛出现的时间

Fig.4 Onset time of secondary island for Lx=25 with By0

图5 By0=3.0时不同时刻电流密度Jy的分布图(a)t=100; (b) t=300; (c) t=500; (d)t=600

Fig.5 Evolution of current density Jy for By0=3.0 at different time (a)t=100; (b) t=300; (c) t=500; (d)t=600

图6 By0=2.0时不同尺寸Lx在t=200时电流密度Jy的分布图(a) Lx=20; (b) Lx=25; (c) Lx=30

Fig.6 Evolution of current density Jy with different Lx for By0=2.0 at t=200 (a) Lx=20; (b) Lx=25; (c) Lx=30

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