Collaborative Research: Super-Alfvenic propagation of energy released during magnetic reconnection in the Earth's magnetotail

磁重联在磁尾动力学中起着基础性的作用，通过重新配置磁拓扑来释放存储的磁能。从重联点向外传播的能量的性质对于我们理解瞬变磁尾现象，如突发性体流、偶极锋面和亚暴具有重要意义。虽然航天器已直接测量到由重新连接加速的体离子流，并将其与极光的产生联系在一起，但这种能量的传播速度仅限于阿尔芬速度，有证据表明，能量的传播速度必须快于阿尔芬速度，才能解释亚暴的发生。然而，人们不太了解的是与动能电子动力学有关的超AlfvéNic能量流，这种能量流往往发生在磁分离附近。与霍尔动力学有关的该区域的四极磁场已被证明是动力学Alfvén波(KAW)的表现，它传播的超Alfvénnn平行于磁场，并产生与高能电子流相关的大量Poynting磁通。这项研究将研究控制重联能超AlfvéNic传播的基本物理机制，主要集中在中尾区。这项研究将使用动力学细胞内粒子模拟(PIC)和从星团和THEMIS航天器重新连接的卫星观测。这应该是理解重联开始和瞬变磁尾现象之间的因果关系的重要一步，例如突发性块流、偶极锋面和亚暴开始。然而，这项研究的潜在好处超出了磁尾研究的范围，因为重联能量的传播对于广泛的自然等离子体和实验室等离子体来说是一个重要的问题。

Magnetic reconnection plays a fundamental role in magnetotail dynamics, reconfiguring magnetic topology to release stored magnetic energy. The nature of the energy propagating away from the reconnection site has implications for our understanding of transient magnetotail phenomena such as bursty bulk flows, dipolarization fronts and substorms. While bulk ion flows accelerated by reconnection have been measured directly by spacecraft and have been linked to the generation of aurora the propagation speed of this energy is limited to the Alfvén speed and there is evidence that energy must propagate faster than the Alfvén speed to account for substorm onset. Less well understood, however, are super-Alfvénic flows of energy associated with kinetic electron dynamics which tend to occur near the magnetic separatrices. The quadrupolar magnetic fields in this region associated with Hall dynamics have been shown to be the manifestation of a kinetic Alfvén wave (KAW) that propagates super-Alfvénically parallel to the magnetic field and generates substantial Poynting flux associated with energetic electron streams. This investigation will study the basic physics mechanisms controlling the super-Alfvénic propagation of reconnection energy with focus roughly on the mid-tail region. The study will use kinetic particle-in-cell simulations (PIC) and satellite observations of reconnection from the Cluster and THEMIS spacecraft. This should be a significant step towards understanding the causal relationships between reconnection onset and transient magnetotail phenomena such as bursty bulk flows, dipolarization fronts, and substorm onset. However the potential benefit of this research extends beyond magnetotail research because propagation of reconnection energy is an important problem for a wide range of natural plasmas and laboratory plasmas.