Effect of Acceleration and Escape of Energetic Particles on Spectral Steepening at Shocks
Effect of Acceleration and Escape of Energetic Particles on Spectral Steepening at Shocks
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DOI：
10.3847/1538-4357/abd699
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发表时间：
2020-12
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影响因子：
--
通讯作者：
F. Fraschetti
中科院分区：
文献类型：
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作者：
F. Fraschetti
行星际激波的高能粒子谱通常在较窄的动量范围内表现出幂定律，在较高的能量范围内软化。我们引入了一个考虑粒子加速和逃逸的输运方程，扩散是由靠近激波的自生湍流和远在上游的预先存在的湍流贡献的。与扩散激波加速滚动相比，上游粒子强度在距激波一个扩散长度范围内变陡。动量谱受激波压缩、速度、远上游扩散系数和激波逃逸时间等宏观参数的控制，可以简化为对数抛物线，也可以简化为破缺的幂定律。在上游均匀扩散系数的情况下，求出了常用的幂/指数截止解。
Energetic particles spectra at interplanetary shocks often exhibit a power law within a narrow momentum range softening at higher energy. We introduce a transport equation accounting for particle acceleration and escape with diffusion contributed by self-generated turbulence close to the shock and by preexisting turbulence far upstream. The upstream particle intensity steepens within one diffusion length from the shock as compared with diffusive shock acceleration rollover. The momentum spectrum, controlled by macroscopic parameters such as shock compression, speed, far-upstream diffusion coefficient, and escape time at the shock, can be reduced to a log-parabola and also to a broken power law. In the case of upstream uniform diffusion coefficient, the largely used power-law/exponential cutoff solution is retrieved.