磁场重联离子扩散区中磁层冷等离子体的动理学研究

在日地耦合过程中，磁场重联是磁能和等离子体能量转换的关键机制，磁层中源于电离层的冷等离子体经常能参与日侧磁层顶和夜侧磁尾的重联过程。目前对重联离子扩散区中冷等离子体动理学的系统研究仍很匮乏。在本项目中，我们将利用磁层多尺度（MMS）卫星的高精度观测数据首次研究磁尾磁场重联中的冷离子扩散区，系统性探索不同等离子体和磁场环境中冷离子扩散区存在的普遍性，定量估算冷离子在广义欧姆定律中的相对贡献，分析冷等离子体和背景等离子体在重联扩散区附近激发的动理学波动，揭示波动对冷等离子体加热的作用。本项目将提升对冷等离子体影响磁场重联的机制认识。

Magnetic reconnection is the key mechanism to transform and transport the magnetic field energy and the plasma energy in the solar wind-magnetosphere coupling system. Cold plasmas of ionospheric origin were found in the magnetic reconnection process at the dayside magnetopause and nightside magnetotail. The effect of cold plasmas in reconnection ion diffusion region is seldom studied so far. In this project, we will use the high-resolution observations from NASA’s Magnetospheric Multiscale (MMS) mission to investigate the cold plasmas inside the ion diffusion region. We will survey all the MMS observations of the dayside magnetopause and nightside magnetotail for ion diffusion region crossings with cold plasmas. The frozen-in condition for cold ions will be analyzed in detail to reveal the existence of cold-ion diffusion region in different plasma and magnetic field environment. The convection electric field term of cold ions will be estimated to evaluate the contribution in the generalized Ohm’s law. We will study the kinetic waves generated by the interaction of cold and hot plasmas and the incidental wave-plasma interaction. This study will provide physical mechanisms of the effect of ionospheric cold plasmas in magnetic reconnection.