用蒙特卡罗方法计算2004年7月电子暴事件对星上分系统的内部充电效应

在太阳的剧烈爆发事件期间，空间环境中的带电粒子能量和通量都得到显著增强，有时使卫星介质发生严重的内部充电而导致星上系统发生故障.但由于粒子与介质相互作用的过程较为复杂，以往一般采用粒子射入介质的经验公式对带电粒子在介质中的沉积进行模拟计算，而近年来蒙特卡洛方法逐渐成为能够进行更准确模拟的有效办法.本文以2004年7月底至8月初的空间天气事件为例，用基于蒙特卡罗方法的GEANT工具包模拟空间高能电子在卫星分系统的印刷电路板（PCB）中的沉积，计算由于内部充电效应造成的PCB内部电场的强度.利用该计算方法，并基于此次事件期间GOES卫星对空间高能粒子环境的监测数据，得到的计算结果表明这次事件期间的空间高能电子暴可能使星上介质发生显著的内部充电，并可能是此期间在轨航天器上发生的一些仪器运行异常的原因.本文采用的蒙特卡罗方法计算内部充电效应方法可以应用于对复杂位形和结构的星上系统的计算，结果可作为卫星抗辐射设计的参考，以有效应对灾害性的空间天气事件.

A Monte carlo study on internal charging of onboard subsystem during the July 2004 energetic electron event

Internal dielectric charging (IDC) is a significant hazard to satellites which are exposed to the space radiation environment,especially to those passing through the Earth's radiation belts. As known,solar events,such as flares,CMEs,SPEs and electron storms,are the primary causes of satellite anomalies. In ground simulations of IDC effect,the Monte Carlo method is more sophisticated to deal with dielectrics of complicated geometry and the complexity of interactions between particles and materials. It should work better than some empirical equations which are usually involved. In this paper,we present a case study to evaluate IDC effect,utilizing GEANT toolkit which is based on the Monte Carlo method. The space event of July 2004 is taken as an example,and the energetic electron flux measured by GOES SEM is used as the particles environment data. To examine the impact of IDC on some structure rather than simplified planar dielectric,a generalized cubic onboard subsystem is constructed,with shields on each side and 10 Printed Circuit Boards (PCB) inside. The GEANT toolkit is utilized to simulate the interaction of injecting elections with the shields and PCBs' dielectric and the electron deposition. The maximum electron field strength inside these PCBs is calculated,which helps evaluate quantitatively the effect of IDC and its relation to energetic particles environment. In this case,a strong field in the dielectric is derived,which is enough to cause a 'potential hazard' of breakdown. This may be related to some intense anomalies of satellite in orbit during this storm event. Accordingly,the method introduced here can facilitate the vulnerability assessment in the shield design,and reduce the risk of operational satellite systems from IDC damage.