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Alternative TitleEffects of the solar wind background field on the numerical simulation of the Solar Energetic Particle(SEP) transportation
魏稳稳; 沈芳; 左平兵; 秦刚; 杨子才
Source Publication地球物理学报
Keyword太阳高能粒子 磁场 太阳风 行星际输运
Other AbstractSolar energetic particles(SEPs) pose one of the most serious hazards to spacecraft systems and constrain human activities in space. Thus, it is of importance to forecast SEP events. Several theories and numerical models are applied to simulate SEP events. Each model makes some assumptions to simplify the complex acceleration and transportation processes within such events. In general, SEP will interact with ambient solar wind and background magnetic field during transportation. It is recognized that interplanetary transport effects must be taken into account at any analysis of SEP propagation. In the previous simulation, it always assumed Parker magnetic field and fixed solar wind speed as the input parameters. However, these assumptions are too simple when compared with the real conditions. In order to get better results, it is necessary to use more accurate background conditions. Recently, we change the fixed solar wind speed into spatial-dependent speed profile based on Parker's theory, and replace the Parker magnetic field with another Parker-like magnetic field based on in situ data at 1 AU. By solving the focused transport equation with simulation of time-backward stochastic processes method, our results show that:(1) Under fast solar wind speed assumption, it is clear that the omnidirectional flux decreases faster than that for the situation with slow solar wind speed in the decay phase. We suggest that it is due to the adiabatic cooling effect. Fast solar wind speed has a significant effect on the adiabatic cooling, which leads the SEPs to lose energy more quickly during transportation. However, slow solar wind speed has less impact on the time profiles of SEP flux and anisotropy. We also compare the time profiles of SEP event observed at different observatories and energies, the results remain the same as previous;(2) When applying in situ data of magnetic field observed by WIND during different Carrington Rotations, the omnidirectional flux time profiles vary greatly, and the main results are as followings:the peak flux appears to be delayed, multi-peak occur, anisotropy also has some differences.We think it results from the magnetic field polarity, which affects the pitch angle, and, furthermore, modulates the momentum. The characteristics are similar in solar minimum and solar maximum, while the peaks seem to be more when solar activity is active. We conclude that the real magnetic field polarity may exert a significant influence during the propagation of SEP. In the future, we will try to use the real-time background conditions which obtain from MHD models in our simulations, in order to make a thorough study of the SEP propagation.
Indexed BySCI ; EI ; CSCD
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Document Type期刊论文
Corresponding Author沈芳
Recommended Citation
GB/T 7714
魏稳稳,沈芳,左平兵,等. 太阳高能粒子(SEP)传播数值模拟中的太阳风背景场研究[J]. 地球物理学报,2016,59(3):767-777.
APA 魏稳稳,沈芳,左平兵,秦刚,&杨子才.(2016).太阳高能粒子(SEP)传播数值模拟中的太阳风背景场研究.地球物理学报,59(3),767-777.
MLA 魏稳稳,et al."太阳高能粒子(SEP)传播数值模拟中的太阳风背景场研究".地球物理学报 59.3(2016):767-777.
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