论文标题

PSP观察到的0.3AU内MHD湍流的波组成,传播和极化

Wave Composition, Propagation, and Polarization of MHD Turbulence within 0.3AU as Observed by PSP

论文作者

Zhu, Xingyu, He, Jiansen, Verscharen, Daniel, Duan, Die, Bale, Stuart D.

论文摘要

湍流是行星际空间中普遍存在的现象,对于在多个尺度上的空间等离子体的能量转化至关重要。这项工作着重于0.3AU内太阳风湍流的繁殖,极化和波形组成特性,以及在MHD尺度上以HeliePentric距离的变化(从航天器框架中的10s到1000)。 We present the probability density function of propagation wavevectors (${\rm{PDF}}(k_\parallel,k_\perp)$) for solar wind turbulence winthin 0.3 AU for the first time: (1) wavevectors cluster quasi-(anti-)parallel to the local background magnetic field for $kd_{\rm i}<0.02$, where $ d _ {\ rm i} $是离子惯性长度; (2)WaveVectors以$ kd _ {\ rm i}> 0.02 $转移到准垂直方向。根据我们的波组成诊断,我们发现:向外/反肺AlfVén模式在整个尺度和距离范围内占主导地位,内向/日光快速模式的光谱能量密度分数随着距离而降低,并且向内的分数能量密度降低,并且向内慢模式的距离降低。向外的快速模式和内向alfvén模式代表了在探索范围和尺度范围内的少数群体。平均而言,根据最小变化方向定义的磁波动的各向异性程度随着规模的增加而降低,在所有尺度上都没有距离的趋势。我们的结果提供了对内气球内太阳风波动/湍流的运输和转移情况的全面见解。

Turbulence, a ubiquitous phenomenon in interplanetary space, is crucial for the energy conversion of space plasma at multiple scales. This work focuses on the propagation, polarization and wave composition properties of the solar wind turbulence within 0.3AU, and its variation with heliocentric distances at MHD scales (from 10s to 1000s in the spacecraft frame). We present the probability density function of propagation wavevectors (${\rm{PDF}}(k_\parallel,k_\perp)$) for solar wind turbulence winthin 0.3 AU for the first time: (1) wavevectors cluster quasi-(anti-)parallel to the local background magnetic field for $kd_{\rm i}<0.02$, where $d_{\rm i}$ is the ion inertial length; (2) wavevectors shift to quasi-perpendicular directions for $kd_{\rm i}>0.02$. Based on our wave composition diagnosis, we find that: the outward/anti-sunward Alfvén mode dominates over the whole range of scales and distances, the spectral energy density fraction of the inward/sunward fast mode decreases with distance, and the fractional energy densities of the inward and outward slow mode increase with distance. The outward fast mode and inward Alfvén mode represent minority populations throughout the explored range of distances and scales. On average, the degree of anisotropy of the magnetic fluctuations defined with respect to the minimum variation direction decreases with increasing scale, with no trend in distance at all scales. Our results provide comprehensive insight into the scenario of transport and transfer of the solar wind fluctuations/turbulence in the inner heliosphere.

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