The role of entropy in magnetotail dynamics
The role of entropy in magnetotail dynamics
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DOI：
10.1029/2008ja014015
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
J. Birn;S. Zaharia;M. Hesse;K. Schindler
中科院分区：
文献类型：
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作者：
J. Birn;S. Zaharia;M. Hesse;K. Schindler
在磁流体力学理论和模拟的基础上，讨论了磁层动力学中的熵守恒和损失的作用，特别是与亚暴相有关的作用，并与PIC模拟进行了比较以进行验证。熵守恒似乎是导致亚暴发展后期薄嵌入电流片形成和潜在平衡丧失的关键因素。在通量管(气泡、突发性大块流动)的向地面输送过程中，熵损失(以等离子体的形式)是必不可少的。熵损失还会改变尾部的稳定性属性，并可能使气球模式不稳定，从而导致交叉尾部的可变性。我们通过理论和模拟的结果来说明这些影响。熵守恒还支配着进化的最终状态的可及性和可能释放的能量的数量。
The role of entropy conservation and loss in magnetospheric dynamics, particularly in relation to substorm phases, is discussed on the basis of MHD theory and simulations, using comparisons with PIC simulations for validation. Entropy conservation appears to be a crucial element leading to the formation of thin embedded current sheets in the late substorm growth phase and the potential loss of equilibrium. Entropy loss (in the form of plasmoids) is essential in the earthward transport of flux tubes (bubbles, bursty bulk flows). Entropy loss also changes the tail stability properties and may render ballooning modes unstable and thus contribute to cross-tail variability. We illustrate these effects through results from theory and simulations. Entropy conservation also governs the accessibility of final states of evolution and the amount of energy that may be released.