Ionospheric convection response to changes of interplanetary magnetic field B z component during strong B y component
Ionospheric convection response to changes of interplanetary magnetic field B z component during strong B y component
复制标题
强B y 分量期间电离层对流对行星际磁场B z 分量变化的响应
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
T. Moretto
中科院分区：
文献类型：
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作者：
Chaosong Huang;D. Murr;G. Sofko;W. Hughes;T. Moretto
众所周知，电离层对流模式受到行星际磁场(IMF)的强烈控制。人们对电离层对流对货币基金组织变化的反应越来越感兴趣。一些研究发现，电离层流量在接近中午时先发生变化，然后在子午面附近发生变化，这被解释为新产生的对流单体在尖点区的传播或扩展。其他研究表明，对流模式对国际货币基金组织重新定位的响应在空间上是固定的。本文研究了强IMF By过程中电离层对流对IMF Bz变化的响应。1995年3月23日，Bx很小，By为强正(7-1nT)，1300UT后Bz的极性发生了多次变化。白天电离层对流主要由一个大的顺时针对流团主导。单元格中心(对流型的中心)向北位于正午区域，向南位于午后区域。结果表明，Bz向南转弯后，单体焦点由正午时段移至午后时段，而Bz方向向北转弯时，正午时段则相反。然而，对流单体的运动，或对流模式中最大的变化，大致限于前一个单体焦点和新单体焦点之间的区域。在这个区域之外，电离层流动可以大大增强或减弱，而对流模式的形状变化很小。当By足够强时，Bz重新定向会引起流动强度的变化，但不会改变对流图案的形状。结果表明，强By期间电离层对流响应的特征表明，对流重构不仅受Bz变化的影响，而且受稳定的大By的显著影响。
It is well established that ionospheric convection patterns are strongly controlled by the interplanetary magnetic field (IMF). There has been an increased interest in ionospheric convection response to IMF changes. Some studies found that ionospheric flows change first near noon and later near the dawn-dusk meridian plane, which is interpreted as propagation or expansion of newly generated convection cells in the cusp region. Other studies showed that the change in convection pattern in response to IMF reorientations is spatially fixed. In this paper, we investigate the ionospheric convection response to IMF B z changes during strong IMF B y . On March 23, 1995, B x was small, B y was strongly positive (7-1 nT), and the B z polarity changed several times after 1300 UT. The dayside ionospheric convection is dominated by a large clockwise convection cell. The cell focus (the eye of the convection pattern) is located in the prenoon sector for northward B z and in the postnoon sector for southward B z . It is found that the cell focus shifts from the prenoon sector to the postnoon sector following a southward B z turning and vice versa for a northward B z turning. However, the motion of the convection cell, or the largest change in the convection pattern, is limited roughly to the region between the previous cell focus and the new cell focus. Outside this region, the ionospheric flows could be greatly enhanced or weakened, while the convection pattern shape changes very little. When B y is strong enough, the B z reorientation causes changes in the flow intensity but not in the shape of the convection pattern. The results show the characteristics of ionospheric convection response during strong B y and suggest that the convection reconfiguration is not only determined by the changing B z but also significantly influenced by the stable and large B y .