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arXiv 1606.04656physics.plasm-ph
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正负电子等离子体的回旋稳定性理论

Gyrokinetic stability theory of electron-positron plasmas

Per Helander, J. W. Connor

摘要:

磁约束电子-正电子等离子体的线性回旋动力学稳定性的参数制度,最有可能是相关的第一个实验室实验,涉及这样的等离子体,密度是足够小,碰撞可以忽略不计和德拜长度大大超过回旋半径的研究。虽然等离子体β很小,电磁效应被保留,但磁压缩性可以忽略不计。因此,先前出版物(Helander,2014)的工作扩展到包括电磁不稳定性,这在闭合场线配置中非常重要,其中这种不稳定性可以在任意低压下发生。研究发现,如果磁场是均匀的,则完全不存在回旋动力学不稳定性:任何不稳定性都必须涉及磁曲率或磁剪切。此外,在偶极磁场中,波长超过德拜半径的交换模的稳定性阈值与理想磁流体力学中的一致。在这个阈值以上,如果温度梯度足够大,准线性粒子通量被向内引导,导致密度分布的自发峰化。

英文摘要:

The linear gyrokinetic stability properties of magnetically confined electron-positron plasmas are investigated in the parameter regime most likely to be relevant for the first laboratory experiments involving such plasmas, where the density is small enough that collisions can be ignored and the Debye length substantially exceeds the gyroradius. Although the plasma beta is very small, electromagnetic effects are retained, but magnetic compressibility can be neglected. The work of a previous publication (Helander, 2014) is thus extended to include electromagnetic instabilities, which are of importance in closed-field-line configurations, where such instabilities can occur at arbitrarily low pressure. It is found that gyrokinetic instabilities are completely absent if the magnetic field is homogeneous: any instability must involve magnetic curvature or shear. Furthermore, in dipole magnetic fields, the stability threshold for interchange modes with wavelengths exceeding the Debye radius coincides with that in ideal MHD. Above this threshold, the quasilinear particle flux is directed inward if the temperature gradient is sufficiently large, leading to spontaneous peaking of the density profile.

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