Pitch-Angle Anisotropy Controls Particle Acceleration and Cooling in Radiative Relativistic Plasma Turbulence
Pitch-Angle Anisotropy Controls Particle Acceleration and Cooling in Radiative Relativistic Plasma Turbulence
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俯仰角各向异性控制辐射相对论等离子体湍流中的粒子加速和冷却
DOI：
10.1103/physrevlett.127.255102
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发表时间：
2021
影响因子：
8.6
通讯作者：
Sironi, Lorenzo
中科院分区：
文献类型：
--
作者：
Comisso, Luca;Sironi, Lorenzo
自然界最强大的高能光源能够将粒子加速到高能量，并在极短的时间尺度上将其辐射出去，甚至比系统的光穿越时间还短。尽管存在大量的辐射损失，但目前尚不清楚什么物理过程可以产生如此有效的加速。通过对细胞内辐射粒子的模拟，我们发现在强同步加速器冷却下，磁主导的对等离子体湍流在几个涡流周转时间内产生具有硬幂律范围（斜率）的非热粒子谱。在突然冷却之前，低俯角粒子可以显著超过标称辐射反应极限。随着时间的推移，粒子光谱变得更加困难（），因为粒子冷却具有能量依赖的俯仰角各向异性。由此产生的同步加速器光谱很难（处理）。我们的发现对于理解来自高能天体物理源的非热发射具有重要意义，特别是来自蟹状星云的伽马射线暴和伽马射线耀斑的提示阶段。
Nature’s most powerful high-energy sources are capable of accelerating particles to high energy and radiating it away on extremely short timescales, even shorter than the light crossing time of the system. It is yet unclear what physical processes can produce such an efficient acceleration, despite the copious radiative losses. By means of radiative particle-in-cell simulations, we show that magnetically dominated turbulence in pair plasmas subject to strong synchrotron cooling generates a nonthermal particle spectrum with a hard power-law range (slope) within a few eddy turnover times. Low pitch-angle particles can significantly exceed the nominal radiation-reaction limit, before abruptly cooling down. The particle spectrum becomes even harder () over time owing to particle cooling with an energy-dependent pitch-angle anisotropy. The resulting synchrotron spectrum is hard (with). Our findings have important implications for understanding the nonthermal emission from high-energy astrophysical sources, most notably the prompt phase of gamma-ray bursts and gamma-ray flares from the Crab nebula.