Early acceleration of electrons and protons at the nonrelativistic quasiparallel shocks with different obliquity angles  

作　　者：Jun Fang Chun-Yan Lu Jing-Wen Yan Huan Yu 

机构地区：[1]Department of Astronomy,Key Laboratory of Astroparticle Physics of Yunnan Province,Yunnan University,Kunming 650091,China [2]Department of Physical Science and Technology,Kunming University,Kunming 650214,China

出　　处：《Research in Astronomy and Astrophysics》2019年第12期298-304,共7页天文和天体物理学研究（英文版）

基　　金：partially supported by the National Key R&D Program of China (2018YFA0404204);the National Natural Science Foundation of China (11873042 and 11563009);the Yunnan Applied Basic Research Projects (2016FB001 and 2018FY001(-003));partially supported by the Yunnan Applied Basic Research Projects (2016FD105);the Candidate Talents Training Fund of Yunnan Province (2017HB003);the Program for Excellent Young Talents, Yunnan University (WX069051 and 2017YDYQ01);the foundations of Yunnan Province (2016ZZX180 and 2016DG006);Kunming University (YJL15004 and XJL15015)

摘　　要：The early acceleration of protons and electrons in the nonrelativistic collisionless shocks with three obliquities are investigated through 1D particle-in-cell simulations. In the simulations, the charged particles possessing a velocity of 0.2c flow towards a reflecting boundary, and the shocks with a sonic Mach number of 13.4 and an Alfven Mach number of 16.5 in the downstream shock frame are generated.In these quasi-parallel shocks with the obliquity angles θ = 15°, 30° and 45°, some of the protons and the electrons can be injected into the acceleration processes, and their downstream spectra in the momentum space show a power law tail at a time of 1.89 × 10^5ω^-1pe, where ωpe is the electron plasma frequency.Moreover, the charged particles reflected at the shock excite magnetic waves upstream of the shock. The shock drift acceleration is more prominent with a larger obliquity angle for the shocks, but the accelerated particles diffuse parallel to the shock propagation direction more easily to participate in the diffusive shock acceleration. In the early acceleration stage, more energetic protons and electrons appear in the downstream of the shock for θ = 15° compared with the other two obliquities. Moreover, in the upstream region, the spectrum of the accelerated electrons is the hardest for θnB = 45° among the three obliquities, whereas the proton spectra for θnB = 15° and 45° are similar as a result of the competition of the effectiveness of the shock drift acceleration and the diffusive shock acceleration.The early acceleration of protons and electrons in the nonrelativistic collisionless shocks with three obliquities are investigated through 1D particle-in-cell simulations. In the simulations, the charged particles possessing a velocity of 0.2c flow towards a reflecting boundary, and the shocks with a sonic Mach number of 13.4 and an Alfven Mach number of 16.5 in the downstream shock frame are generated.In these quasi-parallel shocks with the obliquity angles θ = 15°, 30° and 45°, some of the protons and the electrons can be injected into the acceleration processes, and their downstream spectra in the momentum space show a power law tail at a time of 1.89 × 105ωpe-1, where ωpe is the electron plasma frequency.Moreover, the charged particles reflected at the shock excite magnetic waves upstream of the shock. The shock drift acceleration is more prominent with a larger obliquity angle for the shocks, but the accelerated particles diffuse parallel to the shock propagation direction more easily to participate in the diffusive shock acceleration. In the early acceleration stage, more energetic protons and electrons appear in the downstream of the shock for θ = 15° compared with the other two obliquities. Moreover, in the upstream region, the spectrum of the accelerated electrons is the hardest for θnB = 45° among the three obliquities, whereas the proton spectra for θnB = 15° and 45° are similar as a result of the competition of the effectiveness of the shock drift acceleration and the diffusive shock acceleration.

关 键 词：acceleration of particles methods:numerical shock waves 

分 类 号：P172.4[天文地球—天文学] P145.3