Southward interplanetary magnetic field (IMF) causes the generation of penetration electric fields in the ionosphere at middle and low latitudes. Penetration efficiency, which is defined to be the ratio of the change of the equatorial ionospheric zonal electric field to the change of the dawn-dusk (E_y) component of the interplanetary electric field, is used to represent the quantitative relationship between interplanetary and ionospheric electric fields. We have searched equatorial vertical ion drift data measured by the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar over 19 years (2001–2019) for penetration electric fields when the correlation between interplanetary and ionospheric electric fields is greater than 0.8. In total, 450 penetration electric field events are identified. It is found that the penetration efficiency peaks near noon and decreases afterward. The penetration efficiency depends on the rate of change of E_y with time, the initial E_y when the IMF starts to turn southward, and the change in E_y between the beginning of the IMF southward turning and the subsequent northward turning. The initial E_y is well-correlated with the change in E_y. A positive initial E_y or a smaller change in E_y results in a higher penetration efficiency. The quantitative dependence of penetration efficiency on the structures of E_y is derived for the first time. The results of this study are expected to improve the accuracy of prediction of penetration electric fields.

中文翻译：

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穿透电场效率对行星际电场的依赖性

南向行星际磁场（IMF）导致中低纬度电离层产生穿透电场。穿透效率，定义为赤道电离层纬向电场变化与黎明-黄昏变化之比（E _y) 行星际电场分量，用于表示行星际电场和电离层电场之间的定量关系。当行星际和电离层电场之间的相关性大于 19 年（2001-2019 年）时，我们搜索了由 Jicamarca 无人值守电离层和大气长期调查 (JULIA) 雷达测量的赤道垂直离子漂移数据0.8. 总共识别出 450 个穿透电场事件。发现穿透效率在中午附近达到峰值，之后降低。渗透效率取决于E _y随时间的变化率、IMF 开始向南转向时的初始E _y以及E _y在IMF 南转开始和随后的北转之间。初始E _y与E _y的变化密切相关。正的初始é _ý或更小的变化ê _ÿ导致较高的渗透效率。首次推导出穿透效率对E _y结构的定量依赖性。该研究的结果有望提高穿透电场预测的准确性。