Origin of Mercury's double magnetopause: 3D hybrid simulation study with A.I.K.E.F.
Origin of Mercury's double magnetopause: 3D hybrid simulation study with A.I.K.E.F.
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DOI：
10.1016/j.icarus.2011.12.028
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发表时间：
2012-03-01
期刊：
影响因子：
3.2
通讯作者：
Pringle, Gavin J.
中科院分区：
文献类型：
--
作者：
Mueller, Joachim;Simon, Sven;Pringle, Gavin J.
在第一次和第二次水星飞越期间，信使号探测器在Hermean磁层内探测到黎明侧的双电流片，被标记为“双磁层顶”（Slavin，J.A.等人[2008]。Science 321，85）。这个双重电流片限制了一个磁场减弱的区域，该区域被称为水星的“昼侧边界层”（安德森，M.，Slavin，J.，北，H。[2011年]。星球Space Sci.）到目前为止，双流片，边界层和导致其形成的关键过程还没有得到很好的理解。为了进一步了解这一地区，我们进行了自洽等离子体模拟的Hermean磁层的混合模拟程序A.I.K.E.F.。（Muller，J.，Simon，S.，Motschmann，U.，Schule，J.，Glassmeier，K.，Pringle，G. J.[2011年]。Comput.物理通信182，946-966）。磁场和等离子体结果与信使号的观测结果非常一致。与以前的推测相反，我们的结果证明了这种双电流片可能存在于纯太阳风氢等离子体中，即不存在任何像钠这样的外逸层离子。两股海流的方向相似，但外侧海流的强度更强。虽然外部电流片可以被认为是“经典”磁层顶，但磁层顶和水星表面之间的内部电流片显示是由源于水星内磁层质子压力梯度的反磁电流维持的。压力梯度的存在是由于质子被困在闭合的磁场线上，并在北极和南极之间镜像。在信使号使命期间观察到的昼侧和夜侧反磁减少表明是我们标记为水星“边界层电流”的反磁电流的直接后果。(C)2012 Elsevier Inc. All rights reserved.
During the first and second Mercury flyby the MESSENGER spacecraft detected a dawn side double-current sheet inside the Hermean magnetosphere that was labeled the "double magnetopause" (Slavin, J.A. et al. [2008]. Science 321, 85). This double current sheet confines a region of decreased magnetic field that is referred to as Mercury's "dayside boundary layer" (Anderson, M., Slavin, J., North, H. [2011]. Planet. Space Sci.). Up to the present day the double current sheet, the boundary layer and the key processes leading to their formation are not well understood. In order to advance the understanding of this region we have carried out self-consistent plasma simulations of the Hermean magnetosphere by means of the hybrid simulation code A.I.K.E.F. (Muller, J., Simon, S., Motschmann, U., Schule, J., Glassmeier, K., Pringle, G.J. [2011]. Comput. Phys. Commun. 182, 946-966). Magnetic field and plasma results are in excellent agreement with the MESSENGER observations. In contrast to former speculations our results prove this double current sheet may exist in a pure solar wind hydrogen plasma, i.e. in the absence of any exospheric ions like sodium. Both currents are similar in orientation but the outer is stronger in intensity. While the outer current sheet can be considered the "classical" magnetopause, the inner current sheet between the magnetopause and Mercury's surface reveals to be sustained by a diamagnetic current that originates from proton pressure gradients at Mercury's inner magnetosphere. The pressure gradients in turn exist due to protons that are trapped on closed magnetic field lines and mirrored between north and south pole. Both, the dayside and nightside diamagnetic decreases that have been observed during the MESSENGER mission show to be direct consequences of this diamagnetic current that we label Mercury's "boundary-layer-current". (C) 2012 Elsevier Inc. All rights reserved.