Magnetospheric convection from Cluster EDI measurements compared with the ground-based ionospheric convection model IZMEM
Magnetospheric convection from Cluster EDI measurements compared with the ground-based ionospheric convection model IZMEM
复制标题
Cluster EDI 测量的磁层对流与地基电离层对流模型 IZMEM 的比较
DOI：
10.5194/angeo-27-3077-2009
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发表时间：
2009
影响因子：
1.9
通讯作者：
A. Levitin
中科院分区：
文献类型：
--
作者：
M. Förster;Y. Feldstein;S. Haaland;L. Dremukhina;L. Gromova;A. Levitin
摘要。在超过7年半的时间里（2001-2008年），对南北极帽区进行了群聚/EDI电子漂移观测，得出了夏季条件下高纬度电势分布的统计模型。基于行星际磁场（IMF）在GSM y-z平面上不同方向的势图，导出了基本对流势图（BCP），它代表了行星际磁场依赖于IMF的主要电势分布特征。bcp包括与imf无关的势分布和模式，描述了对正和负IMFBz和IMFBy变化的依赖。整套bcp可以在合理的范围内描述地球磁层顶附近任何太阳风IMF条件下高纬度电势（电离层对流）的时空变化。利用地面磁力计观测得到的IZMEM电离层对流模式与Cluster/EDI模式的比较表明，该模式的基本模式及其变化与IMF模式吻合较好。统计模型表明，当向北IMFBz+≤2 nT时，极帽内存在双胞体反向太阳对流，而当向北IMFBz+≈4-5 nT时，高纬日间扇区内出现一个向太阳对流区，该对流区表现为两个附加胞体之间的向太阳对流，形成高纬对流的四胞体对流格局。在足够强的北向IMFBz条件下，在±IMFBy贡献的依赖下，发生了向三单元对流模式的转变。
Abstract. Cluster/EDI electron drift observations above the Northern and Southern polar cap areas for more than seven and a half years (2001–2008) have been used to derive a statistical model of the high-latitude electric potential distribution for summer conditions. Based on potential pattern for different orientations of the interplanetary magnetic field (IMF) in the GSM y-z-plane, basic convection pattern (BCP) were derived, that represent the main characteristics of the electric potential distribution in dependence on the IMF. The BCPs comprise the IMF-independent potential distribution as well as patterns, which describe the dependence on positive and negative IMFBz and IMFBy variations. The full set of BCPs allows to describe the spatial and temporal variation of the high-latitude electric potential (ionospheric convection) for any solar wind IMF condition near the Earth's magnetopause within reasonable ranges. The comparison of the Cluster/EDI model with the IZMEM ionospheric convection model, which was derived from ground-based magnetometer observations, shows a good agreement of the basic patterns and its variation with the IMF. According to the statistical models, there is a two-cell antisunward convection within the polar cap for northward IMFBz+≤2 nT, while for increasing northward IMFBz+ there appears a region of sunward convection within the high-latitude daytime sector, which assumes the form of two additional cells with sunward convection between them for IMFBz+≈4–5 nT. This results in a four-cell convection pattern of the high-latitude convection. In dependence of the ±IMFBy contribution during sufficiently strong northward IMFBz conditions, a transformation to three-cell convection patterns takes place.