Inferred Linear Stability of Parker Solar Probe Observations Using One- and Two-component Proton Distributions
Inferred Linear Stability of Parker Solar Probe Observations Using One- and Two-component Proton Distributions
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DOI：
10.3847/1538-4357/abd7a0
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发表时间：
2021-01
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通讯作者：
K. Klein;J. Verniero;B. Alterman;S. Bale;A. Case;J. Kasper;K. Korreck;D. Larson;E. Lichko;R. Livi;M. McManus;M. Martinović;A. Rahmati;M. Stevens;P. Whittlesey
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作者：
K. Klein;J. Verniero;B. Alterman;S. Bale;A. Case;J. Kasper;K. Korreck;D. Larson;E. Lichko;R. Livi;M. McManus;M. Martinović;A. Rahmati;M. Stevens;P. Whittlesey
太阳广阔大气层的炎热和扩散性质使其能够在非平衡状态下持续足够长的时间，从而可能出现波粒不稳定性并改变膨胀太阳风的演化。确定出现哪些不稳定性，以及它们在控制太阳风动力学方面发挥的重要作用，是一个长达数十年的过程，涉及在各种径向距离进行现场观测。通过帕克太阳探测器（PSP）的新测量，我们可以研究太阳附近驱动的波模式，并计算针对不同的底层粒子群模型预测的不稳定性。我们使用两种常用的底层速度分布描述，对 PSP 与太阳的第四个近日点期间质子相空间密度的 PSP/SPAN-i 测量的两个小时间隔进行建模。计算并比较了与两个模型相关的线性稳定性和增长率。我们发现，两个选定的区间都容易受到共振不稳定性的影响，尽管增长率和驱动不稳定的模式类型取决于质子是使用一种还是两种成分进行建模。在某些情况下，预测的增长率足够大，足以与其他动态过程竞争，例如能量的非线性湍流转移，与太阳径向距离较大时相对较慢的不稳定性形成鲜明对比。
The hot and diffuse nature of the Sun’s extended atmosphere allows it to persist in non-equilibrium states for long enough that wave–particle instabilities can arise and modify the evolution of the expanding solar wind. Determining which instabilities arise, and how significant a role they play in governing the dynamics of the solar wind, has been a decades-long process involving in situ observations at a variety of radial distances. With new measurements from the Parker Solar Probe (PSP), we can study what wave modes are driven near the Sun, and calculate what instabilities are predicted for different models of the underlying particle populations. We model two hours-long intervals of PSP/SPAN-i measurements of the proton phase-space density during the PSP’s fourth perihelion with the Sun using two commonly used descriptions for the underlying velocity distribution. The linear stability and growth rates associated with the two models are calculated and compared. We find that both selected intervals are susceptible to resonant instabilities, though the growth rates and kinds of modes driven unstable vary depending on whether the protons are modeled using one or two components. In some cases, the predicted growth rates are large enough to compete with other dynamic processes, such as the nonlinear turbulent transfer of energy, in contrast with relatively slower instabilities at larger radial distances from the Sun.