The dayside reconnection X line
The dayside reconnection X line
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DOI：
10.1029/2002ja009381
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发表时间：
2002-10
影响因子：
--
通讯作者：
T. Moore;M. Fok;M. Chandler
中科院分区：
文献类型：
--
作者：
T. Moore;M. Fok;M. Chandler
[1] 反平行重联假说指出，重联发生在磁鞘场和磁层场反平行且磁场的重联分量最大的轨迹处或附近。最近的观察表明，在远小于反平行场剪切的区域中，重新连接率很高。我们探索了替代组件重连假设，即重连沿着通过积分远离具有最大重连场大小的区域的局部 X 线 (XL) 方向确定的轨迹发生。我们对磁层顶的磁层和磁鞘磁场进行了描述，计算了磁层和边界层场之间的角度，以及磁层顶各处的重新连接分量。然后，我们从重新连接分量最大的一个或多个起点对整个磁层顶的 XL 进行积分。正如预期的那样，由此产生的 XL 位于南风 Bz 的赤道下太阳磁层顶上。对于由 By 主导的典型行星际磁场 (IMF) 条件，XL 向极倾斜并围绕尖点进入高纬度区域，与喉状尖点区域流一致。对于偏北的 Bz，XL 分为高纬度和低纬度部分，仅对于主要偏北的 Bz，日下重联消失。我们认为分量重联 XL 代表磁层顶上准稳态重联的平均位置，当然会受到行星际磁场和等离子体的不均匀性和变化的影响。我们得出的结论是，对于大多数 IMF 时钟角度来说，在太阳下磁层顶上的重联率应该很高，而对于向北的 Bz，在高纬度地区重联率更高。
[1] The antiparallel reconnection hypothesis states that reconnection occurs at or near the locus along which magnetosheath and magnetospheric fields are antiparallel and the reconnecting component of the magnetic field is maximal. Recent observations have pointed toward significant reconnection rates in locales with much less than antiparallel field shear. We explore the alternative component reconnection hypothesis that reconnection occurs along a locus determined by integrating the local X line (XL) direction away from that region with the largest reconnecting field magnitude. We develop a description of the magnetospheric and magnetosheath magnetic fields at the magnetopause, compute the angle between the sheath and boundary layer fields, and the reconnecting component, everywhere on the magnetopause. We then integrate the XL across the magnetopause from a starting point or points where the reconnecting component is maximal. The resultant XL lies across the equatorial subsolar magnetopause for southerly Bz, as expected. For typical interplanetary magnetic field (IMF) conditions dominated by By, the XL tilts poleward and loops around the cusps into the high-latitude regions, consistent with throat-like cusp region flows. For northerly Bz, the XL bifurcates into high-latitude and low-latitude segments with subsolar reconnection disappearing only for mainly northward Bz. We argue that the component reconnection XL represents the mean location of quasi-steady reconnection on the magnetopause, subject to of course to nonuniformities and variations of the interplanetary magnetic field and plasma. We conclude that reconnection should have appreciable rates across the subsolar magnetopause for most IMF clock angles, with higher rates at high latitudes for northward Bz.