2 AU以内的“渐进型”太阳高能粒子事件模拟

Modeling a Realistic “Gradual” SEP Event within 2 AU

太阳高能粒子(Solar Energetic Particle,SEP)事件是影响地球空间以及深空辐射环境的主要因素之一。"渐进型"太阳高能粒子事件中的高能粒子主要来自于日冕物质抛射(Coronal Mass Ejection,CME)所驱动的激波扩散加速(Diffusive Shock Acceleration,DSA)过程。CME驱动的激波在行星际的传播过程中,其结构不断演化,进而影响到高能粒子的加速过程。本文利用二维太阳高能粒子加速和传播模型,对发生于2014年4月18日的太阳高能粒子事件实例进行了数值模拟。模型考察了黄道面上2 AU的距离以内包含地球所在位置的4个不同点,分别计算了每个点上高能粒子的通量。数值模拟的结果表明:黄道面内不同位置的观察点,与激波波前的磁力线连接不同,从而导致观察点处高能粒子的通量有着显著的差异。该模型的计算结果可以为深空探测计划开展辐射环境研究提供必要的输入。

Coronal Mass Ejection(CME)-driven shocks,as a primary source of Solar Energetic Particles(SEP),can evolve significantly while propagating away from the Sun. Their characteristics are crucial to understand the underlying particle acceleration mechanism,considered to be the Diffusive Shock Acceleration(DSA) process. Modeling the propagation of CMEdriven shocks and the consequent DSA process is important to both space weather research and forecasting. By utilizing an improved particle acceleration and transport model,a realistic "gradual"SEP event that happened on April 18 th,2014 was modelled. Four locations in the ecliptic plane within 2 Astronomical Units(AU)from the Sun,including the location of the Earth,are examined with the model. Our results show that shock geometry plays a very important role in determining the energetic particle fluxes.