扩散激波加速能达到稳态吗？来自帕克太阳探测器观测到的近太阳激波的见解
Does Diffusive Shock Acceleration Reach Steady State? Insights from a Near-Sun Shock Observed by Parker Solar Probe
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中文总结 AI 辅助
本研究利用帕克太阳探测器对近太阳激波的观测，发现扩散激波加速未达稳态，波增长而非激波年龄限制粒子约束能量。
中文摘要 AI 辅助
无碰撞激波以粒子在其自身产生的波中的扩散系数所决定的速率加速粒子。理论仅在稳态下确定该系数，且尚无测量检验演化中的激波是否达到该状态。我们报告帕克太阳探测器在0.24天文单位处观测到的一次快速、近平行行星际激波，该激波在爆发后四小时被遇到，上游波及其散射的质子记录在同一条磁场线上。仅从波谱我们推导出0.05-30 MeV质子的平行平均自由程，按能量和距激波距离分辨。测量到的压缩波动的镜力提供了通过回旋共振无法达到的俯仰角的散射。平均自由程随距离的增长几乎与稳态自生解所要求的一致，但稳态平衡仅在约1.3 MeV的一个能量处成立。强度轮廓比测量系数预测的浅两倍，因为波仍在增长。约束在2.3至6 MeV之间失效，开始于激波年龄所允许值的两倍以下。其自身粒子驱动的波的增长，而非其年龄或大小，限制了演化激波所约束的能量。
英文摘要
Collisionless shocks accelerate particles at a rate set by the diffusion coefficient of those particles in waves they themselves generate. Theory fixes that coefficient only in steady state, and no measurement has tested whether an evolving shock ever reaches that state. We report Parker Solar Probe observations of a fast, near-parallel interplanetary shock at 0.24 au, encountered four hours after eruption, with the upstream waves and the protons they scatter recorded on the same magnetic field line. From the wave spectra alone we derive the parallel mean free path of 0.05-30 MeV protons, resolved in energy and in distance from the shock. The mirror force of the measured compressive fluctuations supplies the scattering through the pitch angles that gyroresonance cannot reach. The mean free path grows with distance nearly as the steady self-generated solution requires, yet the steady balance holds at one energy only, near 1.3 MeV. The intensity profiles are a factor of two shallower than the measured coefficient predicts, because the waves are still growing. Confinement fails between 2.3 and 6 MeV, beginning a factor of two below what the age of the shock allows. The growth of the waves its own particles drive, rather than its age or its size, limits the energy an evolving shock confines.
发表机构
- University of Turku（图尔库大学）
- University of California, San Diego（加州大学圣迭戈分校）
- Eureka Sci.（尤里卡科学公司）
- KU Leuven（荷语鲁汶大学）
- Centre for mathematical Plasma Astrophysics, KU Leuven（荷语鲁汶大学数学等离子体天体物理学中心）
- Space Sciences Laboratory, University of California, Berkeley（加州大学伯克利分校空间科学实验室）
- National Taras Shevchenko University of Kyiv（基辅塔拉斯舍甫琴科国立大学）
- The Johns Hopkins University Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）
- California Institute of Technology（加州理工学院）
机构由 AI 辅助整理，请以论文原文为准。
