基于SWARM双星观测的场向电流的经度变化

本文利用SWARM A和C双星高精度的矢量磁场数据研究了不同季节高纬地区场向电流(FACs)随地磁经度和地方时的变化情况.研究发现:在南北半球,FACs存在明显的经度变化,南半球FACs的变化强度大约是北半球的1.2～3.2倍.利用潮汐谱分析法我们发现FACs中占主导的非迁移潮汐分量为DW2和D0.在春秋和夏季半球,DW2波更为明显.D0波可用太阳光照的经度变化来解释,向阳侧靠近磁极的经度带比远离磁极的经度带有更强的太阳光照射.DW2波则与地磁场强度和地磁倾角等因素有关.全球电离层与热层模型计算的FACs中D0波占主导,且中性风和对流电场对D0波的贡献几乎相当.

SWARM dual satellite observations of longitudinal variations in field-aligned currents

In this study we investigate the longitudinal variations in the mean densities of field-aligned currents (FACs) at high latitudes in different seasons, by using high resolution magnetic field data from SWARM A and C satellites. Longitudinal variations are about a factor of 1.2~3.2 larger in the Southern Hemisphere than in the Northern Hemisphere. A tidal analysis is applied to FACs. D0 and DW2 are the dominant non-migrating components. DW2 is larger than D0 in summer and equinox. The longitudinal variations in solar illumination can explain D0 wave in FACs, with more solar illumination at near pole longitudes than at far-from-pole longitude. Factors like the geomagnetic field strength and dipole tilt angle might contribute to the observed DW2 features in FACs. The FACs simulated by the global ionosphere and thermosphere model only show D0 wave. The theoretical study reveals that the role of neutral wind is comparable to that of the electric field in the formation of D0 wave.