Four cells or two? Are four convection cells really necessary?
Four cells or two? Are four convection cells really necessary?
复制标题
四格还是两格？
DOI：
10.1029/93ja01992
复制
发表时间：
1994
影响因子：
--
通讯作者：
R. Heelis
中科院分区：
文献类型：
--
作者：
P. Reiff;R. Heelis
本文讨论的问题是否需要在极冠电离层的四细胞对流模式的观测，或数据是否完全可以解释的（也许是高度扭曲的）两细胞对流模式。我们目前的对流数据从大气探测器C，其中，如果只有在向阳-反向阳方向的流动分量进行测量，可以解释为两个可能的扭曲的两个细胞模式或作为一个完整的四细胞模式之一。然而，无论是扭曲的两个细胞的模式，是一致的向阳-antisunward流组件可以在整个航天器的轨迹一致的黎明-黄昏流组件，而不假设一个严重的流扭结和额外的场对准电流向阳的航天器轨道。此外，零势点（在四胞模型中，这将标志着两个反向对流胞之间的划分）也正好对应于气流中东西向分量反转的位置，这是四胞模型预测的特征，但在扭曲的两胞模型中更难解释。由于这种模式在两次连续的经过中重复，时间变化可能被排除为向日气流的原因。在两个北方半球的向阳面通道之间，一个南半球的向阳面通道也显示了极冠中的向阳流区域。事实上，在这种情况下，向日流动并不局限于向阳面，这也有利于四胞解释。
This paper addresses the question whether a four-cell convection pattern in the polar cap ionosphere is required by observations, or whether the data are fully explainable by a (perhaps highly distorted) two-cell convection pattern. We present convection data from Atmosphere Explorer C, which, if only the flow component in the sunward-antisunward direction were measured, could be explained either as one of two possible distorted two-cell patterns or as a full four-cell pattern. However, neither of the distorted two-cell patterns that are consistent with the sunward-antisunward flow component can be made consistent with the dawn-dusk flow component over the entire spacecraft trajectory, without postulating a severe flow kink and extra field-aligned currents sunward of the spacecraft track. In addition, the zero potential point (which in a four-cell model would mark the division between the two reverse convection cells) also exactly corresponded to the location of the reversal of the east-west component in the flow, a feature predicted from the four-cell model but more difficult to explain in a distorted two-cell model. Because the pattern was repeated on two consecutive passes, time variations can probably be ruled out as a cause of the sunward flow. Between the two northern hemisphere dayside passes, a southern hemisphere nightside pass also showed a region of sunward flow in the polar cap. The fact that in this case the sunward flow was not confined to the dayside also favors a four-cell explanation.