A possible explanation for the enhancement of energetic particles downstream of the heliospheric termination shock
A possible explanation for the enhancement of energetic particles downstream of the heliospheric termination shock
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DOI：
10.1088/1742-6596/1332/1/012020
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
L. L. Zhao-L.;G. Zank;L. Adhikari
中科院分区：
文献类型：
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作者：
L. L. Zhao-L.;G. Zank;L. Adhikari
旅行者2号对能量从1.8 MeV到40 MeV的高能粒子“时间-强度”剖面的观测表明，通量峰值出现在日球终端激波（HTS）的下游，这与经典的扩散激波加速（DSA）的预测不一致。以往的研究表明，冲击是有效的产生下游磁通绳，岛或等离子体团。这些动态相互作用的小尺度结构可以通过与重连相关的过程在统计上加速带电粒子。我们提出了一个初步的研究磁场和等离子体的性质与高能粒子的数据在V2交叉的高温超导体。我们应用与太阳风磁岛动力学相关联的局部随机加速模型来解释在高温超导体附近观测到的高能粒子的异常行为。从Zank等人的统计输运理论推导出的粒子速度分布函数的解析解被用来拟合高温超导体下游观测到的粒子通量放大。结果表明，磁岛的随机加速可以成功地预测：（i）粒子强度峰值出现在高温超导体后面，而不是激波前沿;（ii）粒子通量放大因子随粒子能量的增加而增加;（iii）粒子强度峰值与高温超导体之间的距离随粒子能量的增加而增加;这项研究说明了由于磁岛的动力学相互作用，在内日鞘局部加速的可能性。
Voyager 2 observations of the energetic particle “time-intensity” profiles from ~1.8 to ~40 MeV show that the flux peaks downstream of the heliospheric termination shock (HTS), which is inconsistent with the predictions of classical diffusive shock acceleration (DSA). Previous studies suggest that shocks are effective in generating downstream magnetic flux ropes, islands or plasmoids. These dynamically interacting small-scale structures can accelerate charged particles statistically through reconnection-related processes. We present a preliminary study of the magnetic field and plasma properties together with the energetic particle data during the V2 crossing of the HTS. We apply a local stochastic acceleration model associated with solar wind magnetic island dynamics to explain the unusual behavior of energetic particles observed in the vicinity of the HTS. An analytic solution for the particle velocity distribution function derived from the Zank et al. statistical transport theory is used to fit the observed particle flux amplification downstream of the HTS. The results show that stochastic acceleration by interacting magnetic islands can successfully predict the observed (i) peaking of particle intensities behind the HTS, instead of at the shock front; (ii) increasing of the particle flux amplification factor with increasing particle energy; and (iii) increase in distance between the particle intensity peak and the HTS with increasing particle energy; This study illustrates the possibility of local acceleration in the inner heliosheath due to the dynamical interaction of magnetic islands.