帕克太阳探测器观测到的近平行行星际激波的波调控前驱体
The Wave-Regulated Precursor of a Near-Parallel Interplanetary Shock Observed by Parker Solar Probe
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中文总结 AI 辅助
研究人员利用帕克太阳探测器观测太阳附近的近平行行星际快激波，首次分辨其上游波场的四个族，揭示了激波加速的上游调控机制。
中文摘要 AI 辅助
扩散激波加速（DSA）存在于从日冕物质抛射到超新星遗迹激波的各类激波中，其前提是存在由被加速粒子自身维持的散射波场，这种自调控机制此前尚未得到原位观测证实。我们报告帕克太阳探测器（Parker Solar Probe）于2023年3月13日在0.24天文单位处观测到的一次速度约2800 km/s的近平行行星际快激波，并将其上游波场划分为四个族，这一分类此前从未在太阳附近的快激波中实现。在共同波数带上存在右旋和左旋圆偏振族，以及沿场线的线偏振族，它们与从激波流出的超热到MeV级质子发生回旋共振：该粒子束驱动了散射自身的场，测得的平均自由程为前驱体尺度的一半，使得粒子束保持足够的各向异性以维持驱动作用。在此环外存在一个弱的斜向线偏振分量，其波功率占比仅为百分之几，这是首次在原位 foreshock（激波前区）中分辨出该分量。其同相密度与场强波动表明压缩部分为快磁声波，并使共振族的回旋共振能量沿前驱体偏移最多13%。0.3天文单位内的激波加速由激波自身构建的上游 foreshock 调控。
英文摘要
Diffusive shock acceleration, at shocks from coronal mass ejections to supernova-remnant blast waves, presupposes a scattering wave field that the accelerated particles themselves maintain. This self-regulation has not been resolved in situ. We report Parker Solar Probe observations of a fast (~2800 km/s), near-parallel interplanetary shock at 0.24 AU on 2023 March 13 and separate its upstream wave field into four families, a classification not made before at a fast shock near the Sun. Right-hand and left-hand circularly polarized families over a common wavenumber band, with a field-aligned linearly polarized family, are cyclotron-resonant with the suprathermal-to-MeV protons streaming from the shock: the beam drives the field that scatters it, and the measured mean free path, half the precursor scale, leaves the beam anisotropic enough to sustain the drive. Outside this loop lies a weak, oblique, linearly polarized component, a few per cent of the wave power, resolved here for the first time at an in situ foreshock. Its in-phase density and field-magnitude fluctuations identify the compressive part as fast magnetosonic and shift the cyclotron-resonance energies of the resonant families by up to 13 % along the precursor. Acceleration at shocks inside 0.3 AU is governed upstream, in a foreshock the shock builds for itself.
