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arXiv 0910.4293physics.plasm-phphysics.space-ph
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线性理论的非模态方法:边缘稳定性和湍流波动的耗散

Non-modal approach to linear theory: marginal stability and the dissipation of turbulent fluctuations

Enrico Camporeale, Thierry Passot, David Burgess

摘要:

线性化系统的非模态方法与正常模式分析不同,它遵循某些扰动平衡的时间演化,因此包括瞬态效应。我们采用非模态的方法研究的双麦克斯韦磁化等离子体的稳定性,使用朗道流体模型,我们简要描述。我们表明,双麦克斯韦稳定平衡可以支持一些物理量的瞬态增长,我们研究这些瞬态行为时,平衡接近其边际稳定的条件。这与各向异性等离子体有关,在太阳风中经常观察到温度各向异性接近可以触发动力学不稳定性的值。用非模态方法得到的结果是有关的线性边际稳定性的概念重新审查。此外,我们还讨论了湍流涨落耗散的问题,建议在未来的研究中应包括非模态方法。

英文摘要:

The non-modal approach for a linearized system differs from a normal mode analysis by following the temporal evolution of some perturbed equilibria, and therefore includes transient effects. We employ a non-modal approach for studying the stability of a bi-Maxwellian magnetized plasma using the Landau fluid model, which we briefly describe. We show that bi-Maxwellian stable equilibria can support transient growth of some physical quantities, and we study how these transients behave when an equilibrium approaches its marginally stable condition. This is relevant to anisotropic plasma, that are often observed in the solar wind with a temperature anisotropy close to values that can trigger a kinetic instability. The results obtained with a non-modal approach are relevant to a re-examination of the concept of linear marginal stability. Moreover, we discuss the topic of the dissipation of turbulent fluctuations, suggesting that the non-modal approach should be included in future studies.

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