发表机构
The University of Texas at Austin; University of California, Berkeley（德克萨斯大学奥斯汀分校; 加州大学伯克利分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用Helios数据，分析内日球层快速太阳风质子的加热速率，发现所有质子群需垂直加热，而核心与束流质子的平行能量演化不同，揭示了湍流与不稳定性及阿尔芬波衰减的作用。
AI 中文摘要
太阳风质子表现出偏离双绝热预测的温度各向异性，这表明存在额外的能量来源。为了研究太阳风加热机制，我们分析了Helios 1和2的数据，并刻画了快速太阳风质子的绝热不变量和各向异性加热速率的径向演化，分别考虑了整体群以及其核心和束流子群。与以往研究不同，我们考虑了质子热通量以及由大幅度涨落引起的对帕克螺旋的偏离，这导致平行加热速率与早期结果相比出现显著差异。尽管早期工作质疑了用幂律估计加热速率的可靠性，并提出研究绝热不变量的径向演化作为更稳健的方法，但我们表明，当应用于同一数据集时，这两种方法产生了一致的结果。我们的分析表明，所有考虑的质子群都需要净垂直加热，这与早期研究一致。相反，平行能量演化在不同质子群之间有所不同。核心质子需要平行加热，而束流质子则经历平行冷却，尽管总质子群经历了净平行冷却。这种行为与湍流和核心-束流动理学不稳定性的联合作用一致，这些不稳定性可以共同驱动优先的垂直加热，同时在快速太阳风中产生平行冷却。核心质子的平行加热则可能是阿尔芬波衰减的特征。
英文摘要
Solar wind protons exhibit a temperature anisotropy that deviates from the double-adiabatic prediction, suggesting an additional energy source. To investigate solar wind heating mechanisms, we analyze Helios 1 and 2 data and characterize the radial evolution of the adiabatic invariants and anisotropic heating rates of fast wind protons, considering both the bulk population and its core and beam components separately. Unlike previous studies, we account for proton heat fluxes and deviations from the Parker spiral caused by large-amplitude fluctuations, which causes significant differences in the parallel heating rates compared to earlier results. Although earlier work has questioned the reliability of power laws to estimate heating rates and proposed as a more robust approach the investigation of the radial evolution of adiabatic invariants, we show that the two approaches yield consistent results when applied to the same dataset. Our analysis shows that all proton populations considered require net perpendicular heating, consistent with earlier studies. In contrast, the parallel energy evolution differs between populations. Core protons require parallel heating, whereas beam protons undergo parallel cooling although the total proton population undergoes a net parallel cooling. This behavior is consistent with the combined action of turbulence and core-beam kinetic instabilities, which together can drive preferential perpendicular heating while simultaneously produce parallel cooling in the fast solar wind. Core proton parallel heating could instead be a signature of Alfvén wave decay.
