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

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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.