Interplanetary magnetic field control of the ionospheric field-aligned current and convection distributions
Interplanetary magnetic field control of the ionospheric field-aligned current and convection distributions
复制标题
DOI：
10.1002/2013ja019455
复制
发表时间：
2014-04-01
影响因子：
2.8
通讯作者：
Imber, S. M.
中科院分区：
文献类型：
--
作者：
Juusola, L.;Milan, S. E.;Imber, S. M.
高纬度电离层对流和场向电流(FAC)是太阳风-磁层-电离层耦合的一种表现形式。通过观察它们，我们可以获得关于磁层顶重新连接的信息，这是一个太阳风能进入磁层的过程。我们分别使用CHAMP卫星和超级双极光雷达网雷达10多年的磁场和对流数据，显示了不同行星际磁场方向和幅度下FAC和对流的联合分布。在IMF向南移动期间，对流遵循已建立的两单体模式，相关区域1和区域2 FAC，表明太阳以下重联。当IMF向北移动时，叠加在一个弱的双单元格型上，有一个反向的双单元格型，相关的0区和1区FAC在白天，表明叶重新连接。对于占主导地位的IMF B-x，B-z的符号决定了是否观测到叶或次太阳重联信号，但与纯粹向北或向南的IMF相比，B-x将减弱信号。当国际货币基金组织从北向旋转到黄昏或黎明时，截然不同的反转和正向双胞格模式开始合并为扭曲的双胞格模式。这与国际货币基金组织B-y将重新连接的位置从开放的波瓣场线移动到关闭的黎明或黄昏场线是一致的，即使国际货币基金组织B-z&>0。随着国际货币基金组织继续向南旋转，扭曲的模式平稳地转变为对称的两单元模式。虽然IMF方向决定了FAC和对流的位形，但IMF的振幅影响它们的强度。
Patterns of the high-latitude ionospheric convection and field-aligned current (FAC) are a manifestation of the solar wind-magnetosphere-ionosphere coupling. By observing them we can acquire information on magnetopause reconnection, a process through which solar wind energy enters the magnetosphere. We use over 10 years of magnetic field and convection data from the CHAMP satellite and Super Dual Auroral Radar Network radars, respectively, to display combined distributions of the FACs and convection for different interplanetary magnetic field (IMF) orientations and amplitudes. During southward IMF, convection follows the established two-cell pattern with associated Region 1 and Region 2 FACs, indicating subsolar reconnection. During northward IMF, superposed on a weak two-cell pattern there is a reversed two-cell pattern with associated Region 0 and Region 1 FACs on the dayside, indicating lobe reconnection. For dominant IMF B-x, the sign of B-z determines whether lobe or subsolar reconnection signatures will be observed, but B-x will weaken the signatures compared to pure northward or southward IMF. When the IMF rotates from northward to duskward or dawnward, the distinct reversed and forward two-cell patterns start to merge into a distorted two-cell pattern. This is in agreement with the IMF B-y displacing the reconnection location from the open lobe field lines to closed dawn or dusk field lines, even though IMF B-z>0. As the IMF continues to rotate southward, the distorted pattern transforms smoothly to that of the symmetric two-cell pattern. While the IMF direction determines the configuration of the FACs and convection, the IMF amplitude affects their intensity.