Magnetosheath Reconnection Before Magnetopause Reconnection Driven by Interplanetary Tangential Discontinuity: A Three‐Dimensional Global Hybrid Simulation With Oblique Interplanetary Magnetic Field
Magnetosheath Reconnection Before Magnetopause Reconnection Driven by Interplanetary Tangential Discontinuity: A Three‐Dimensional Global Hybrid Simulation With Oblique Interplanetary Magnetic Field
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DOI：
10.1029/2018ja025679
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发表时间：
2018-11
期刊：
影响因子：
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通讯作者：
Zhifan Guo;Yu Lin;Xueyi Wang;A. Du
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文献类型：
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作者：
Zhifan Guo;Yu Lin;Xueyi Wang;A. Du
通过对入射太阳风 TD 具有不同磁场旋转角 ΔΦ = 90° 至 180° 和半宽 w = 2di0 至 w = 30di0 的情况进行系统地进行三维全球尺度混合模拟，研究了与行星际切向不连续性 (TD) 携带的南转倾斜行星际磁场 (IMF) 相关的地球日侧动力学，其中 di0 是太阳中的离子惯性长度风。总体而言，TD 在传输到磁鞘时被压缩，在准平行 (Q-||) 和准垂直 (Q-⊥) 冲击下游具有不同的压缩过程。研究发现，磁鞘重联可能发生在 Q-|| 的下游。和 Q-⊥ 激波是由于定向 TD 与弓激波和磁层顶的相互作用而产生的，但磁鞘重联的存在取决于 w 和 ΔΦ。磁鞘磁通绳是通过薄电流片中的三维片状重联形成的，在较大的ΔΦ下具有较长的磁绳长度。磁绳的空间范围存在黎明-黄昏的不对称性，随着 ΔΦ 的减小，这种不对称性变得更加显着。当ΔΦ减小到90°时，没有发现重联磁绳。当具有南转 IMF（向阳面）的磁通量到达磁层顶时，磁层顶重联就会启动，并且磁层顶磁绳可以与磁鞘磁绳混合。我们的模拟表明，IMF 南转的影响可能不是简单的场方向变化，仅导致磁层顶重新连接。
Terrestrial dayside dynamics associated with a southward turning, oblique interplanetary magnetic field (IMF) carried by an interplanetary tangential discontinuity (TD) is investigated by performing a three‐dimensional global‐scale hybrid simulation systematically for cases in which the incoming solar wind TD possesses various magnetic field rotation angles ΔΦ = 90° to 180° and half widths w = 2di0 to w = 30di0, where di0 is the ion inertial length in the solar wind. Overall, the TD is compressed while being transmitted into the magnetosheath, with different compression processes downstream of the quasi‐parallel (Q‐||) and quasi‐perpendicular (Q‐⊥) shocks. It is found that magnetosheath reconnection may take place downstream of both the Q‐|| and Q‐⊥ shocks due to interaction of the directional TD with the bow shock and magnetopause, but the existence of magnetosheath reconnection depends on w and ΔΦ. Magnetosheath flux ropes are formed through three‐dimensional patchy reconnection in the thinned current sheet, with a longer rope lengths under a larger ΔΦ. There exists a dawn‐dusk asymmetry in the spatial extent of the flux ropes, which becomes more significant as ΔΦ decreases. When ΔΦ decreases to 90°, no reconnection flux ropes are found. Magnetopause reconnection is initiated when the magnetic fluxes with a southward turning IMF (on the sunward side) reach the magnetopause, and the magnetopause flux ropes can be mixed with the magnetosheath ones. Our simulation demonstrates that the effects of a southward turning of the IMF may not be a simple field direction change that leads to reconnection only at the magnetopause.