Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.
Science. 2011 Jun 3;332(6034):1183-6. doi: 10.1126/science.1202869.
The sawtooth mode of convection of Earth's magnetosphere is a 2- to 4-hour planetary-scale oscillation powered by the solar wind-magnetosphere-ionosphere (SW-M-I) interaction. Using global simulations of geospace, we have shown that ionospheric O(+) outflows can generate sawtooth oscillations. As the outflowing ions fill the inner magnetosphere, their pressure distends the nightside magnetic field. When the outflow fluence exceeds a threshold, magnetic field tension cannot confine the accumulating fluid; an O(+)-rich plasmoid is ejected, and the field dipolarizes. Below the threshold, the magnetosphere undergoes quasi-steady convection. Repetition and the sawtooth period are controlled by the strength of the SW-M-I interaction, which regulates the outflow fluence.
地球磁层的锯齿状对流模式是一种由太阳风-磁层-电离层（SW-M-I）相互作用驱动的 2 到 4 小时行星尺度的波动。通过对地球空间的全球模拟，我们已经表明，电离层 O(+)外流可以产生锯齿状振荡。随着流出的离子填充内磁层，它们的压力会使夜间的磁场膨胀。当流出通量超过阈值时，磁场张力无法限制积聚的流体；富含 O(+)的等离子体就会被抛出，磁场会去极。低于阈值时，磁层经历准稳态对流。重复和锯齿周期由 SW-M-I 相互作用的强度控制，它调节流出通量。
