【作者】 张青梅；

【导师】 李传起；

【作者基本信息】 南京信息工程大学 ， 空间天气学， 2013， 博士

【摘要】 太阳风-磁层-电离层组成了地球空间的一个复杂的耦合体系,基于不同行星际条件或地磁条件下,等离子体层和电离层间物质输运机制仍未弄明。此外,地磁周期扰动,如地磁脉动、电离层等效电流体系对行星际扰动的响应也是空间天气学中值得研究的问题。本文利用中国子午工程(Chinesse Meridian Project)地磁台站观测数据、OMNI数据库中的卫星观测数据及全球磁流体力学(magnetohydrodynamics, MHD)数值模型对以上两个方面的问题进行研究。1、等离子体层-电离层的物质传输机制首先,用地面台站观测ULF波遥感磁层的方法,并结合偶极场模型和等离子体密度模型,我们统计分析了五个磁暴事件期间同时观测的等离子体层密度与电离层电子密度的变化特点。观测结果表明,等离子体层等离子体密度及电离层电子密度同暴前相比有所减少,并且电离层电子密度的减少先于等离子体层等离子体密度的减少,因而,表明等离子体层的削减很可能是由于电离层的等离子体供应减少引起的,进一步表明电离层是可能控制着等离子体层动力学行为的因素之一。其次,除磁暴事件之外,我们也分析了地磁平静期间太阳风动压脉冲条件下等离子体层密度和电离层电子密度的变化特点,发现地磁平静时期等离子体层在太阳风动压脉冲作用下出现削减,而电离层电子密度与磁暴期间变化相反。结果表明太阳风动压脉冲之后的行星际南向磁场和变化较大的晨昏电场可能是导致等离子体层密度减少的主要原因,变化的行星际条件和电离层可能共同控制着等离子体层的密度变化。2、地磁场的周期扰动对行星际条件的响应我们从地面观测和模拟两方面研究地磁场的周期扰动对行星际条件的响应。地磁脉动用于表示短周期的地磁扰动。我们研究了中国子午工程子午链上分布的一些地面台站观测到的Pc3-4地磁脉动的时空分布特征及其产生源机制。结果表明中低纬度的Pc3-4地磁脉动分布存在明显的晨昏不对称性,在昼侧出现的Pc3-4地磁脉动与行星际上游波动密切相关,高速太阳风更易导致地磁脉动的增强；而在近赤道低纬区域,均未能观测到Pc3-4地磁脉动表明存在明显的纬度效应。其次,行星际激波是导致地球磁层-电离层系统发生扰动的重要原因之一,它可以通过对磁层-电离层系统电流体系的改变来影响地磁变化。电离层等效电流体系(Equivalent Current Systems, ECS)是一种表征地面磁场的复杂、大尺度时空响应的简便方法,它假定地面地磁场的变化是由流动在电离层薄层的电流引起的。我们用全球三维磁流体模型(PPMLR-MHD)分析了行星际激波作用下电离层等效电流体系的即时响应。结果表明激波过后等效电流体系图像逐渐演化为激波下游行星际条件控制的典型图像。这个响应过程与行星际激波强度有关。更多还原

【Abstract】 A complex coupling system is formed by the solar wind, magnetosphere and ionosphere in geospace. And an important process in geospace that is still not fully understood is the plasma transport between the plasmasphere and the ionosphere during different interplanetary disturbance and geomagnetic condition. Additionally, the response of the periodic disturbance of the geomagnetic field, for example, geomagnetic pulsation and ECS, to the interplanetary disturbance, is paid attention on studying the problem in space weather. In the paper, we use the observation data of Chinese Meridian Project and OMNI database by satellites and global3-D MHD model to answer above two mentioned questions.1、Transport process of the plasmasphere and ionosphereFirstly, using the method of remote sensing magnetosphere using ground-based observations of ULF waves, combined with the dipole magnetic field model and plasma density model, we analysis statistically the changing of simultaneous observations of the plasmaspheric and ionospheric densities during five moderate magnetic storms. The observations show that the plasmaspheric density drops significantly more than the prestorm value. The ionospheric electron density reductions take place before the plasmaspheric density reaches its minimum. These findings suggest that the plasmaspheric depletion is very likely due to the reduced plasma supply from the ionosphere. Therefore, the plasmasphere dynamics seems to be controlled by the ionosphere during magnetic storms.Secondly, besides magnetic storms, we study the changing of the plasmaspheric and ionospheric densities in response to solar wind dynamic pressure pulsation during the geomagnetic quite period. The result suggests the plasmasphere in response to the solar wind dynamic pressure pulsation shows a significant depletion. However, the ionospheric electron density first increases and then decreases to the origin level, which is opposite to the behavior during magnetic storms. Preliminary analysis shows that the plasmaspheric depletion may be mainly caused by the interplanetary southward magnetic field and changing dawn-dusk electric field. The plasmaspheric density variations seem to be controlled by both the IMF and ionospheric conditions.2、The response of the periodic disturbance of the geomagnetic field to interplanetary conditionWe study the periodic perturbation of the geomagnetic field in response to the interplanetary disturbance from observation and numerical simulation. The geomagnetic pulsation is defined as the short periodic geomagnetic disturbance.We analysis the source and the characteristics of Pc3-4geomagnetic pulsation in spatial and temporal distribution. Preliminary results show there is the significant dawn-dusk asymmetric distribution of the Pc3-4geomagnetic pulsations in the middle-low latitudes, with Pc3-4pulsations activity observed mainly in the pre-noon sector, during both time periods. They are closely related to the interplanetary conditions, with high-speed solar wind leading to the enhancement of the Pc3-4geomagnetic pulsations. However, Pc3-4pulsations activity is not observed near the equatorial low latitudes due to latitudinal effect.Additionally, interplanetary (IP) shocks could affect the geomagnetic field by changing the current systems in the magnetosphere-ionosphere region. Equivalent current systems (ECS) are defined as a simply proxy for the temporal and spatial evolution of the large-scale complex geomagnetic perturbation that it is assumed to be caused by the current in the thin ionosphere layer. We utilize the global3-D MHD model to analysis the instantaneous response of the ionospheric ECS to interplanetary shock. The simulation results suggest ECS images gradually evolve to the shock downstream images by control of the interplanetary condition, which is relevant to the interplanetary shock intensity.更多还原