Ion acceleration processes in magnetic reconnection: Geotail observations in the magnetotail
Ion acceleration processes in magnetic reconnection: Geotail observations in the magnetotail
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DOI：
10.1002/2014ja020737
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发表时间：
2015-03
期刊：
影响因子：
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通讯作者：
T. Nagai;I. Shinohara;S. Zenitani
中科院分区：
文献类型：
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作者：
T. Nagai;I. Shinohara;S. Zenitani
利用Geotail探测器对磁尾磁场重联过程进行了三维离子速度分布函数观测，研究了磁场重联过程中离子流出的形成过程.高达40 keV的离子加速过程可分为两种类型，这两种类型由两步过程组成。第一种是在磁场重联的离子-电子退耦区域的中心部分靠近X线的地方，在那里存在一个强烈的交叉电流层，电子产生高速流出射流。在这一区域内，流入离子和作弯曲运动的离子共存。离子在流入过程中在南北方向上被加速到~10 keV，然后它们在黄昏方向上被重联电场加速得更远。第二种是在磁场重联的离子-电子退耦区的外部远离X线的地方。在该区域内，形成霍尔电流环，流入的霍尔电子存在于分界线层附近。离子在流入过程中被加速并在霍尔电流环内作朝晨运动，然后进一步加速形成朝尾和朝地的流出。在该区域中，大量的离子作为流入物提供，并且形成含有宽能量范围（5-40 keV）的离子的流出物。因此，南北（垂直）电场，这可能是霍尔电场，和黄昏重联电场操作离子加速过程中的磁尾磁场重联。
Ion outflow formation processes in magnetic reconnection are investigated on the basis of 3‐D ion velocity distribution function observations for magnetic reconnection in the magnetotail with the spacecraft Geotail. Ion acceleration processes up to 40 keV can be divided into two types, and these two types consist of two‐step processes. The first type is found close to the X line in the central part of the ion‐electron decoupling region of magnetic reconnection where an intense crosstail current layer exists and electrons make high‐speed outflow jets. In this region, inflowing ions and ions making the meandering motion coexist. Ions are accelerated up to ~10 keV in the north–south direction during the inflowing process, and then they are accelerated farther by the reconnection electric field in the duskward direction. The second type is found far from the X line in the outer parts of the ion‐electron decoupling region of magnetic reconnection. In this region, the Hall current loops are formed and the inflowing Hall electrons exist near the separatrix layers. Ions are accelerated and make the dawnward motion inside the Hall current loop in the inflowing process, and then they are farther accelerated to form tailward and earthward outflows. In this region, significant amount of ions is supplied as inflows, and outflows containing ions in the wide energy range (5–40 keV) are formed. Hence, both the north–south (vertical) electric field, which is probably the Hall electric field, and the duskward reconnection electric field operate ion acceleration processes for magnetic reconnection in the magnetotail.