Schroeder J W R, Howes G G, Kletzing C A, Skiff F, Carter T A, Vincena S, Dorfman S
Department of Physics, Wheaton College, Wheaton, IL, USA.
Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA.
Nat Commun. 2021 Jun 7;12(1):3103. doi: 10.1038/s41467-021-23377-5.
While the aurora has attracted attention for millennia, important questions remain unanswered. Foremost is how auroral electrons are accelerated before colliding with the ionosphere and producing auroral light. Powerful Alfvén waves are often found traveling Earthward above auroras with sufficient energy to generate auroras, but there has been no direct measurement of the processes by which Alfvén waves transfer their energy to auroral electrons. Here, we show laboratory measurements of the resonant transfer of energy from Alfvén waves to electrons under conditions relevant to the auroral zone. Experiments are performed by launching Alfvén waves and simultaneously recording the electron velocity distribution. Numerical simulations and analytical theory support that the measured energy transfer process produces accelerated electrons capable of reaching auroral energies. The experiments, theory, and simulations demonstrate a clear causal relationship between Alfvén waves and accelerated electrons that directly cause auroras.
尽管极光数千年来一直备受关注，但重要问题仍未得到解答。首要问题是极光电离层电子在与电离层碰撞并产生极光之前是如何加速的。人们经常发现强大的阿尔文波以足以产生极光的能量向地球方向传播，但尚未直接测量到阿尔文波将能量传递给极光电离层电子的过程。在此，我们展示了在与极光带相关的条件下，从阿尔文波到电子的能量共振转移的实验室测量结果。通过发射阿尔文波并同时记录电子速度分布来进行实验。数值模拟和分析理论支持所测量的能量转移过程产生能够达到极光能量的加速电子。这些实验、理论和模拟表明了阿尔文波与直接导致极光的加速电子之间存在明确的因果关系。
