论文标题
质子温度各向异性的条件以驱动太阳风中的不稳定性
Conditions for proton temperature anisotropy to drive instabilities in the solar wind
论文作者
论文摘要
使用来自太阳能轨道的高分辨率数据，我们研究了质子温度各向异性驱动的镜像模式和倾斜的消防型不稳定性所必需的等离子体条件。我们发现，不稳定的等离子体表现出对磁场方向和散装太阳风速之间的角度的依赖性，而仅通过太阳风的双绝热扩张无法解释。角度依赖性表明，Alfvénic风中的垂直加热可能是负责的。我们量化了这两个不稳定性的发生率，这是对航天器上对流的不稳定间隔的长度的函数。该分析表明，镜像和倾斜的消防型不稳定性需要大于2至3个不稳定波长的空间间隔，以便将等离子体放松到边缘稳定的状态，从而更接近太阳风中的热力学平衡。我们的分析表明，这些不稳定性的条件在局部有效地在范围内有效地变化得比太阳风湍流的相关长度短得多。
Using high-resolution data from Solar Orbiter, we investigate the plasma conditions necessary for the proton temperature anisotropy driven mirror-mode and oblique firehose instabilities to occur in the solar wind. We find that the unstable plasma exhibits dependencies on the angle between the direction of the magnetic field and the bulk solar wind velocity which cannot be explained by the double-adiabatic expansion of the solar wind alone. The angle dependencies suggest that perpendicular heating in Alfvénic wind may be responsible. We quantify the occurrence rate of the two instabilities as a function of the length of unstable intervals as they are convected over the spacecraft. This analysis indicates that mirror-mode and oblique firehose instabilities require a spatial interval of length greater than 2 to 3 unstable wavelengths in order to relax the plasma into a marginally stable state and thus closer to thermodynamic equilibrium in the solar wind. Our analysis suggests that the conditions for these instabilities to act effectively vary locally on scales much shorter than the correlation length of solar wind turbulence.
