Firehose instabilities triggered by the solar wind suprathermal electrons
Firehose instabilities triggered by the solar wind suprathermal electrons
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DOI：
10.1093/mnras/sty3377
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发表时间：
2018-11
影响因子：
4.8
通讯作者：
S. M. Shaaban;S. M. Shaaban;S. M. Shaaban;M. Lazar;M. Lazar;R. A. López;H. Fichtner;S. Poedts
中科院分区：
文献类型：
--
作者：
S. M. Shaaban;S. M. Shaaban;S. M. Shaaban;M. Lazar;M. Lazar;R. A. López;H. Fichtner;S. Poedts
在缺乏碰撞的空间等离子体中，例如太阳风、地球磁层，动力学不稳定性被认为是限制等离子体粒子温度各向异性的主要因素，但只有在确定了它们在这些环境中的性质后，才能给出明确的答案。目前的研究描述了在空间等离子体中普遍存在的超热电子集居存在的情况下电子火管不稳定性的全谱。超热电子同时刺激周期和非周期分支，值得注意的是非周期模式斜向传播到周围磁场所显示的效应，显著超过Lazar等人最近报道的平行(周期)分支的生长速度(2017a，MNRAS 464,564)。在超热电子存在的情况下，这种不稳定性的各向异性阈值也会降低，这预示着太阳风条件下的有效性会增强。这些结果可能也适用于其他各种天体物理环境，在这些环境中，消防管不稳定性涉及太阳耀斑、磁场重联地点、吸积流或导致日球层、星际介质和星系团中的激波和同向旋转相互作用的等离子体喷流。
In collision-poor plasmas from space, e.g., solar wind, terrestrial magnetospheres, kinetic instabilities are expected to play a major role in constraining the temperature anisotropy of plasma particles, but a definitive answer can be given only after ascertaining their properties in these environments. Present study describes the full spectrum of electron firehose instabilities in the presence of suprathermal electron populations which are ubiquitous in space plasmas. Suprathermal electrons stimulate both the periodic and aperiodic branches, remarkable being the effects shown by the aperiodic mode propagating obliquely to the ambient magnetic field which markedly exceeds the growth rates of the parallel (periodic) branch reported recently in Lazar et al., (2017a, MNRAS 464, 564). Derived exclusively in terms of the plasma parameters, the anisotropy thresholds of this instability are also lowered in the presence of suprathermal electrons, predicting an enhanced effectiveness in the solar wind conditions. These results may also be relevant in various other astrophysical contexts where the firehose instabilities involve, e.g., solar flares, sites of magnetic field reconnection, accretion flows or plasma jets leading to shocks and co-rotating interactions in heliosphere, interstellar medium and galaxy clusters.