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arXiv 2407.04044physics.plasm-ph
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电子热性质对空间等离子体中Alfvén波色散性质的作用

The role of the thermal properties of electrons on the dispersion properties of Alfvén waves in space plasmas

Nicolás Villarroel-Sepúlveda, Pablo S. Moya, Rodrigo A. López, Daniel Verscharen

AI总结:

本文在全动能线性理论下研究了电子热性质对Alfvén波极化及从EMIC到KAW转变的影响,发现温度比$T_e/T_p$在动能尺度对极化有显著影响,且暖等离子体中KAW的物理过程不可忽略电子惯性。

摘要:

背景。从左旋到右旋极化Alfvén波的转变取决于波数、动能与磁压之比$β$、温度各向异性以及等离子体的离子成分。与温度各向异性一样,电子与质子的温度比$T_e/T_p$对于表征等离子体的热性质具有极大相关性。该比值在不同的空间等离子体环境之间变化显著。因此,研究该比值的变化如何影响电磁波的极化性质,对于我们理解空间等离子体的动力学变得高度相关。目标。我们提出了一项广泛的研究,探讨电子热性质对全动能线性理论中Alfvén波特性和行为的影响,以及对从电磁离子回旋(EMIC)波到动力学Alfvén波(KAW)转变的影响。方法。我们在均匀Maxwellian电子-质子等离子体中,求解Alfvén分支倾斜电磁波的全动能色散关系。我们通过改变电子与质子温度比,针对传播角度、$β_p=8πnkT_p/B^2$和波数的不同配置,量化了电子热性质的影响。结果。我们表明,温度比$T_e/T_p$对Alfvén模式的极化具有强烈且非平凡的影响,特别是在动能尺度和$β_e+β_p>0.5$时。我们得出结论,在暖等离子体区域中,电子惯性在KAW的动能尺度物理中起着重要作用,因此在用于计算机模拟的混合模型中不能被排除。

英文摘要:

Context. The transition from left-hand to right-hand polarized Alfvén waves depends on the wavenumber, the ratio of kinetic to magnetic pressure $β$, temperature anisotropy, and ion composition of the plasma. Along with the temperature anisotropy, the electron-to-proton temperature ratio $T_e/T_p$ is of great relevance for the characterization of the thermal properties of a plasma. This ratio varies significantly between different space plasma environments. Thus, studying how variations on this ratio affect the polarisation properties of electromagnetic waves becomes highly relevant for our understanding of the dynamics of space plasmas. Aim. We present an extensive study on the effect of the thermal properties of electrons on the behaviour and characteristics of Alfvénic waves in fully kinetic linear theory, as well as on the transition from electromagnetic ion-cyclotron (EMIC) to kinetic Alfvén waves (KAW). Method. We solve the fully kinetic dispersion relation for oblique electromagnetic waves of the Alfvén branch in a homogenous Maxwellian electron-proton plasma. We quantify the effect of the thermal properties of electrons by varying the electron-to-proton temperature ratio for different configurations of the propagation angle, $β_p=8πnkT_p/B^2$, and wavenumber. Results. We show that the temperature ratio $T_e/T_p$ has strong and non-trivial effects on the polarisation of the Alfvénic modes, especially at kinetic scales and $β_e+β_p>0.5$. We conclude that electron inertia plays an important role in the kinetic scale physics of the KAW in the warm plasma regime, and thus cannot be excluded in hybrid models for computer simulations.

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