极区顶部电离层离子上行-DMSP卫星观测

本文利用DMSP卫星离子漂移速度测量数据,对高纬顶部电离层离子整体上行进行研究,主要考察平静时和磁暴期间离子上行强度与发生率随MLT(晨昏两侧)分布规律的变化；以及磁暴期间强的离子上行与等离子体对流及其剪切之间的关系。研究发现,磁暴期间强上行事件的发生率比平静期高近2倍,发生率的晨昏不对称性出现逆转,由平静时昏侧发生率较大变为磁暴期间晨侧发生率较大；磁暴期间晨侧离子上行速度的分布向速度高端加权,平均速度大于昏侧,最大上行速度远大于昏侧；强的离子上行往往与强对流剪切或强对流本身相伴随。

ION UPFLOW IN THE TOPSIDE POLAR IONOSPHERE-OBSERVATIONS BY THE DMSP SATELLITE

Based on a large dataset of ion drift velocity measurements hoard on DMSP satellite,a study is made on the plasma bulk upflowing in the topside polar ionosphere.The emphasis is put on the storm-time changes in distribution of upflow occurrence and intensity versus MLT (mainly dawn and dusk)in comparison with that during quiet period,as well as the relation- ship between the ion upflow with the plasma convection and its shear.The results show that the storm-time occurrence frequency of upflow events is nearly two times higher than that during quiet period;the dawn-dusk asymmetry for occurrence frequency inversed from favoring dusk- side to favoring dawn-side.On an average,the storm-time velocity of the ion upflow in the dawn sector is larger than that in the dusk,with maximum upflowing velocity much larger than that in dusk sector.The ion upflow is closely related to the plasma convection and its shear, with strong upflow accompanied usually by large convection shear or abnormally large convec- tion itself.