Bi-directional streaming of particles accelerated at the STEREO-A shock on 2008 March 9
Bi-directional streaming of particles accelerated at the STEREO-A shock on 2008 March 9
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DOI：
10.1093/mnras/staa3021
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发表时间：
2020-09
影响因子：
4.8
通讯作者：
F. Fraschetti;J. Giacalone
中科院分区：
文献类型：
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作者：
F. Fraschetti;J. Giacalone
本文对2008年3月9日由日地关系天文台（ST-A）观测到的快速准垂直反向激波附近超热离子的各向异性和强度进行了解释。测量的超热粒子的强度分布表现出增强，或“尖峰”，在冲击到达和俯仰角各向异性的冲击到达之前的时间是双峰，共同建议捕获近散射自由离子沿着磁场线相交的冲击在两个位置。我们运行测试粒子模拟与预先存在的上游静磁波动平流通过冲击。所测得的双峰上游各向异性，近场对齐的各向异性高达约15分钟的上游的冲击，以及“煎饼状”的各向异性高达约10分钟的下游的冲击很好地再现了模拟。这些结果，在协议与早期的工作，建议的主导作用的大尺度结构（100秒的超热质子gyroradii）的磁场在锻造早期的粒子加速冲击。
We present an interpretation of anisotropy and intensity of supra-thermal ions near a fast quasi-perpendicular reverse shock measured by Solar Terrestrial Relations Observatory Ahead (ST-A) on 2008 March 9th. The measured intensity profiles of the supra-thermal particles exhibit an enhancement, or "spike", at the time of the shock arrival and pitch-angle anisotropies before the shock arrival are bi-modal, jointly suggesting trapping of near-scatter-free ions along magnetic field lines that intersect the shock at two locations. We run test-particle simulations with pre-existing upstream magnetostatic fluctuations advected across the shock. The measured bi-modal upstream anisotropy, the nearly field-aligned anisotropies up to ~15 minutes upstream of the shock, as well as the "pancake-like" anisotropies up to ~10 minutes downstream of the shock are well reproduced by the simulations. These results, in agreement with earlier works, suggest a dominant role of the large-scale structure (100s of supra-thermal proton gyroradii) of the magnetic field in forging the early-on particle acceleration at shocks.