Trajectory Analysis of Galactic Cosmic Rays Invading into the Heliosphere
Trajectory Analysis of Galactic Cosmic Rays Invading into the Heliosphere
复制标题
DOI：
10.3847/1538-4357/ac02c2
复制
发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Kotaro Yoshida;S. Matsukiyo;Kesuke Shimokawa;H. Washimi;T. Hada
中科院分区：
文献类型：
--
作者：
Kotaro Yoshida;S. Matsukiyo;Kesuke Shimokawa;H. Washimi;T. Hada
通过数值模拟研究了侵入日光层的银河宇宙线质子的轨迹。首先使用高分辨率 MHD 模拟再现时间静止的全球日光层。然后，对分布在虚拟日球层中的多个测试粒子（质子）的运动进行数值求解。当初始粒子洛伦兹因子为 10 (∼10 GeV) 时，粒子的运动受到反映粒子小陀螺半径的小尺度日光层结构的强烈影响。粒子可以从日光层顶的许多部分（鼻子、侧面和尾部）进入日光层。一旦它们进入，它们就会在磁场局部较弱的区域扩展，例如日球层顶和日光层电流片。另一方面，颗粒难以侵入终止激波的上游。我们发现了多种入侵粒子的轨迹模式，例如电流片漂移、极漂移、螺旋运动、激波漂移和类费米加速。在后两者中，粒子被加速。当初始粒子洛伦兹因子为 1000（∼1 TeV）时，由于粒子的陀螺半径较大，因此对日光层的小尺度结构不敏感。由于与日尾大尺度涡流的共振相互作用，一些粒子表现出偏心运动。其他一些经过日光层的粒子，由于日光层周围星际磁场的瓶颈结构，发生镜面反射，返回进入日光层。
The trajectories of galactic cosmic-ray protons invading the heliosphere are investigated by using numerical simulations. A time stationary global heliosphere is first reproduced by using a high-resolution MHD simulation. Then, motions of a number of test particles (protons) distributed in the virtual heliosphere are numerically solved. When the initial particle Lorentz factor is 10 (∼10 GeV), the motions of particles are strongly affected by small-scale heliospheric structures reflecting the small gyroradii of the particles. Particles can enter the heliosphere from many parts (nose, flank, and tail) of the heliopause. Once they have entered, they expand in the region where the magnetic field is locally weak, such as the heliopause and the heliospheric current sheet. On the other hand, particles have difficulty invading upstream of the termination shock. We found a variety of invading particle trajectory patterns such as current sheet drift, polar drift, spiral motion, shock drift, and Fermi-like acceleration. In the latter two, particles are accelerated. When the initial particle Lorentz factor is 1000 (∼1 TeV), the particles are insensitive to the small-scale structures of the heliosphere due to their large gyroradii. Some particles show eccentric motions due to resonant interaction with the large-scale eddy in the heliotail. Some other particles passing by the heliosphere are mirror reflected due to the bottleneck structure of interstellar magnetic field surrounding the heliosphere and return back to enter the heliosphere.