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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Cluster observations of a cusp diamagnetic cavity: Structure, size, and dynamics
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Cluster observations of a cusp diamagnetic cavity: Structure, size, and dynamics

机译：集群的观察尖端抗磁腔:结构、大小和动力学

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摘要

We have analyzed Cluster magnetic field and plasma data during high-altitude cusp crossing and compared them with high-resolution MHD simulations. Cluster encountered a diamagnetic cavity (DMC) during northward interplanetary magnetic field (IMF) conditions, and as the IMF rotated southward, the spacecraft reencountered the cavity more at the sunward side of the cusp because the reconnection site had changed location. We found evidence of magnetic reconnection both during northward and southward IMF conditions. The Cluster separation was ~5000 km, enabling for the first time measurements both inside the DMC and surrounding boundaries that allowed us to construct the structure of the DMC and put the observations of ion pitch angle distributions in context of local reconnection topology and gradients of the boundaries. The cavity is characterized by strong magnetic field fluctuations and high-energy particles. At the magnetosheath boundary the high-energy particle fluxes reduced by several orders of magnitude. Throughout the magnetosheath, the high-energy proton fluxes remained low except during brief intervals when sc4 and scl dropped back into the cavity due to changes in solar wind dynamic pressure. However, the high-energy O+ fluxes did not drop as much in the magnetosheath and were mostly at 60°-120° pitch angles, indicative of a trapped population in the DMC which is observed in the magnetosheath due to a large gyroradius. Significant fluxes of protons and ionized oxygen were also observed escaping from the diamagnetic cavity antiparallel to the magnetic field in a time scale more consistent with the local DMC source than with a reflected bow shock source.
机译：我们分析了集群磁场和等离子体在高空尖端交叉和数据用高分辨率的磁流体动力相比模拟。在北行星际腔(DMC)磁场(IMF)的条件下,国际货币基金组织旋转向南,飞船重逢朝着太阳的腔更多的尖端因为重新连接网站改变了的位置。重新连接在向北和向南国际货币基金组织的条件。公里,使第一次测量在DMC和周围的边界让我们来构造DMC的结构并将离子螺旋角的观测分布在当地重新连接的上下文中拓扑和梯度的边界。腔的特点是强烈的磁场波动和高能粒子。磁鞘边界的高能粒子通量降低几个数量级。在整个磁鞘中,高能质子通量仍低,除了在简短间隔当sc4和sci回下降腔由于太阳风的变化动态压力。磁鞘并没有下降多少主要是在60°-120°倾斜角度,象征被困人口DMC中观察到磁鞘中由于大型回转半径。重要的质子和电离氧气通量也观察到抗磁性逃离腔中的磁场反平行的时间尺度更符合当地的DMC源与弓形激波反射源。

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