磁尾磁偶极化锋面及其极光电集流效应研究

Understanding the formation and development of the auroral electrojet is crucial for studying substorms. Substorm current wedge is formed by the connection of the magnetospheric current system with auroral electrojet that is caused by both the ionospheric conductivity enhancement from the deposition of auroral particles and field-aligned currents. However, the physical mechanism by which the magnetospheric dynamics affect auroral electrojet is poorly understood. The dipolarization fronts in the magnetotail have a current system with similar polarity of substorm current wedge, however, how this current system contributes to the auroral electrojet is highly controversial. The simultaneous accurate observations of the magnetotail micro-mesoscale dynamics and auroral electrojet provided by recent magnetospheric probes such as MMS and Cluster and the low-altitude satellite Swarm, give us an unprecedented opportunity to approach this question. The project plans to use the observations from MMS, Cluster and Swarm to study: (1) the fine structure of field-aligned currents and their formation mechanisms; (2) the relationship between the field-aligned currents near the magnetotail dipolarization fronts and the auroral electrojet and magnetotail current system’s contribution to the auroral electrojet; (3) the effects of the dipolarization front currents on the auroral electrojet and substorm current wedge under different levels of geomagnetic activity. With the numerical study of the global magnetosphere model and local particle model, we will be able to provide more profound understanding how the magnetotail dynamics affect the formation and evolution of the auroral electrojet.

地球电离层中极光电集流的形成和演化是亚暴研究的核心问题。极光电集流主要由极光粒子沉降导致的电导率增大和场向电流共同造成，与磁层电流体系形成亚暴电流楔。但磁层动力学过程影响极光电集流的物理机制仍不清楚。磁尾磁偶极化锋面在传播过程中形成与亚暴电流楔相似的电流体系，而这一电流体系对极光电集流的贡献具有较大的争议。近期MMS、Cluster等磁层卫星结合近地Swarm卫星可以实现对磁尾中小尺度动力学过程和极光电集流的联合同步观测，为解决这一问题提供了良好的机会。本项目拟利用MMS、Cluster、Swarm等卫星，研究（1）磁尾磁偶极化锋面电流体系的精细结构和形成机制；（2）磁尾磁偶极化锋面场向电流与极光电集流的对应关系及其对极光电集流的贡献；（3）不同地磁活动下磁偶极化锋面电流对极光电集流及亚暴电流楔的影响。结合数值模拟研究，我们可较为深入地了解磁尾动力学过程影响极光电集流形成和演化的物理机制。