Kappa distributions are ubiquitous in space and astrophysical poorly collisional plasmas, such as the solar wind, suggesting that microscopic and macroscopic properties of these non-equilibrium plasmas are highly conditioned by the wave-particle interactions. The present work addresses the evolution of anisotropic bi-Kappa (or bi-$\kappa$-)distributions of electrons triggering instabilities of electromagnetic electron-cyclotron (or whistler) modes. The new quasi-linear approach proposed here includes time variations of the $\kappa$ parameter during the relaxation of temperature anisotropy. Numerical results show that $\kappa$ may increase for short interval of times at the beginning, but then decreases towards a value lower than the initial one, while the plasma beta and temperature anisotropy indicate a systematic relaxation. Our results suggest that the electromagnetic turbulence plays an important role on the suprathermalization of the plasma, ultimately lowering the parameter $\kappa$. Even though the variation of $\kappa$ is in general negative ($\Delta \kappa <0$) this variation seems to depend of the initial conditions of anisotropic electrons, which can vary very much in the inner heliosphere.

中文翻译：

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双卡帕等离子体不稳定性的一般准线性方法。惠斯勒不稳定

Kappa 分布在空间和天体物理不良碰撞等离子体（例如太阳风）中无处不在，这表明这些非平衡等离子体的微观和宏观特性受到波粒相互作用的高度调节。目前的工作解决了电子的各向异性双 Kappa（或 bi-$\kappa$-）分布的演变，这些分布触发了电磁电子回旋加速器（或惠斯勒）模式的不稳定性。这里提出的新准线性方法包括在温度各向异性松弛期间 $\kappa$ 参数的时间变化。数值结果表明，$\kappa$ 在开始时可能会在短时间内增加，然后朝着低于初始值的方向下降，而等离子体β和温度各向异性表明系统弛豫。我们的结果表明，电磁湍流对等离子体的超热化起着重要作用，最终降低了参数 $\kappa$。尽管 $\kappa$ 的变化通常是负的（$\Delta \kappa <0$），但这种变化似乎取决于各向异性电子的初始条件，其在内部日光层中可能变化很大。