晨昏电场对磁亚暴触发的影响

本文讨论了晨昏电场存在时磁尾等离子体片内撕裂模不稳定性的激发和增长问题。得到的结果可以用来解释晨昏电场对磁亚暴的触发以及加快等离子体片贮存能量的耗散等现象。我们推导了存在电场漂移时的撕裂模方程,并在均匀电流片模型下求解了该方程的解析解。结果表明触发不稳定性所允许的临界电流片宽度与电场大小近似成正比,这表明考虑晨昏电场效应后磁亚暴更易被激发。此外对于厚度相同的电流片来说,长波撕裂模的增长率也随晨昏电场的加强而增大。 

The Influence of Dawn-Dusk Electric Field on the Triggering of Magnetospheric Substorm

By studying the ewwect of Exit drift on the tearing mode instability,the influence of dawn-dusk electric field on the triggering of magnetospheric substorm is investigated.The tearing mode equation including the E×B drift term is derived and solved with a step-like electric current distribution.The Calculations show that the critical thickness of the current sheet allowed for the triggering of the tearing mode instability and the growth rate of long wave-length modes both increase with increasing dawn-dusk eleatric field.Therefore as dawn-dusk electric field is enhanced,the magnetospheric substorms are easily generated and the energy stored in the plasma sheet can quickly be released as well.