行星际磁场时钟角与地球磁层开放磁通的关系

地球磁层开放磁通F_pc是研究磁层动力学过程的重要参数之一，其与日侧和夜侧磁尾的磁场重联具有密切关系. 日侧重联率控制稳定状态下磁层开放磁通的大小，主要受各种太阳风条件的影响. 其中，行星际磁场（IMF）的时钟角是影响日侧重联率的一个重要因素. 通过全球MHD模拟，研究了行星际磁场时钟角θ_c与地球磁层开放磁通F_pc 之间的关系. 结果表明，开放磁通F_pc随着行星际磁场时钟角 θ_c逐渐接近180°（纯南向）而逐渐增加，两者之间的关系近似为F_pc∝sin^3/2（θ_c/2）. 由于表征行星际磁场与地球磁场剪切程度的θ_c影响日侧重联率，从而控制F_pc，该关系反映了二者之间的物理联系.

Relationship between interplanetary magnetic field clock angle and magnetosphere open magnetic flux

The open magnetic flux (F_pc) is a key parameter to study magnetospheric dynamical process, which is closely related to magnetic reconnections in the dayside magnetopause and magnetotail. The dayside reconnection rate controls the amount of the open magnetic flux, which is affected by various solar wind parameters, among which the clock angle θ_c of the interplanetary magnetic field (IMF) is an important factor that influence the dayside reconnection rate. Using global MHD simulations, we analyze the relationship between θ_c and F_pc. The results show that the open flux F_pc increases as the clock angle θ_c approaches 180°(due southward), and the open flux F_pc is proportional to sin3/2 (θ_c/2). This reflects the physical connection between them, since θ_c describes the magnitude of the shear between IMF and terrestrial magnetic field, and affects the dayside reconnection rate, thus controlling the open flux F_pc.