Deng X H, Matsumoto H
Nature. 2001 Mar 29;410(6828):557-60. doi: 10.1038/35069018.
Magnetic reconnection has a crucial role in a variety of plasma environments in providing a mechanism for the fast release of stored magnetic energy. During reconnection the plasma forms a 'magnetic nozzle', like the nozzle of a hose, and the rate is controlled by how fast plasma can flow out of the nozzle. But the traditional picture of reconnection has been unable to explain satisfactorily the short timescales associated with the energy release, because the flow is mediated by heavy ions with a slow resultant velocity. Recent theoretical work has suggested that the energy release is instead mediated by electrons in waves called 'whistlers', which move much faster for a given perturbation of the magnetic field because of their smaller mass. Moreover, the whistler velocity and associated plasma velocity both increase as the 'nozzle' becomes narrower. A narrower nozzle therefore no longer reduces the total plasma flow-the outflow is independent of the size of the nozzle. Here we report observations demonstrating that reconnection in the magnetosphere is driven by whistlers, in good agreement with the theoretical predictions.
磁重联在各种等离子体环境中起着关键作用，它为储存的磁能快速释放提供了一种机制。在重联过程中，等离子体形成一个“磁喷嘴”，就像软管的喷嘴一样，其速率由等离子体流出喷嘴的速度控制。但传统的重联图景一直无法令人满意地解释与能量释放相关的短时间尺度，因为这种流动是由重离子介导的，其合成速度较慢。最近的理论研究表明，能量释放反而由一种称为“啸声波”的波中的电子介导，由于电子质量较小，对于给定的磁场扰动，它们的移动速度要快得多。此外，随着“喷嘴”变窄，啸声波速度和相关的等离子体速度都会增加。因此，更窄的喷嘴不再会降低总的等离子体流量——流出量与喷嘴大小无关。在此，我们报告的观测结果表明，磁层中的重联是由啸声波驱动的，这与理论预测高度一致。
