基于ACE飞船观测的银河宇宙线与太阳风变化的统计研究  

Statistical Investigation on the Galactic Cosmic Rays and Solar Wind Variation Based on ACE Observations

作　　者：郭孝城 曹世豪 熊明 GUO Xiaocheng;CAO Shihao;XIONG Ming(State Key Laboratory of Space Weather,National Space Science Center,Chinese Academy of Sciences,Beijing 100190;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049)

机构地区：[1]中国科学院国家空间科学中心空间天气学国家重点实验室,北京100190 [2]中国科学院大学地球与行星科学学院,北京100049

出　　处：《空间科学学报》2020年第6期969-979,共11页Chinese Journal of Space Science

基　　金：中国科学院空间科学战略性先导科技专项(XDB41000000,XDA15052500,XDA1701030);国家自然科学基金项目(41874171,41674146,41574159);中国科学院前沿科学重点研究计划项目(QYZDJ-SSW-JSC028);民用航天技术预先研究项目(D030202,D020301)共同资助。

摘　　要：基于ACE飞船的资料,通过时序迭加方法统计分析了最近两个太阳活动极小年时期(2007.0-2009.0和2016.5-2019.0年)的宇宙线计数与太阳风参数的关系.结果表明,宇宙线的计数受太阳风共转流相互作用区的强烈影响,宇宙线计数变化与快慢太阳风流界面的位置密切相关,例如流界面的穿越通常伴随着宇宙线计数的下降.分析表明,第一时段的具有“雪犁”效应的宇宙线计数下降对应于流界面附近的扩散系数急剧下降,而第二时段的非“雪犁”效应的计数下降可能是由穿越流界面后的扩散系数增大引起的.日球层电流片也与宇宙线计数变化存在一定的相关性,宇宙线粒子在日球层电流片附近存在一定程度的堆积.太阳风对宇宙线的作用机制表明,宇宙线的漂移和扩散效应决定了其在1AU附近的分布变化.Galactic Cosmic Rays(GCRs)are originated from the interstellar medium and modulated by the heliospheric magnetic field when they enter the heliosphere.Based on the GCR and plasma observations from ACE spacecraft,the relation between the GCR counts and the solar wind parameters during the recent two periods of solar minimum(the years of 2007.0-2009.0 and 2016.5-2019.0)was analyzed by means of the Superposed Epoch Analysis(SEA)method.The results indicate that GCRs are strongly modulated by the Corotating Interaction Regions(CIR)in solar wind,the Stream Interfaces(SI)sandwiched between fast and slow solar wind are closely related with the depression of GCR counts.The mechanism of the GCR variation is investigated through the empirical diffusion coefficients.The so-called"snow-plough"effect of GCR variation prior to the SI crossing appears during the first period,then the GCR counts decrease after the crossing,which corresponds to the sudden drop of diffusion coefficient at the SI.However,this effect is not observed for the second period,the decrease of GCR counts are simply caused by the enhancement of the diffusion coefficient after the SI crossing.Moreover,Heliospheric Current Sheet(HCS)correlate with GCR counts well,the GCRs drift along the current sheet and then accumulate to a pileup structure,which is physically balanced between their diffusion and drift effects.Finally,based on the observation and Parker transport theory,we discuss the physical mechanism of the GCR variation for the crossings of SIs and HCS,and proposed that the interplay between drift and diffusion determines the GCR distribution and variation at a heliocentric distance of 1AU.

关 键 词：银河宇宙线 共转流相互作用区 流界面 日球层电流片 

分 类 号：P352[天文地球—空间物理学]