In the dayside foreshock, many foreshock transients have been observed and simulated. Because of their strong dynamic pressure perturbations, foreshock transients can disturb the local bow shock, magnetosheath, magnetopause, and thus the magnetosphere‐ionosphere system. They can also accelerate particles contributing to shock acceleration. Recent observations and simulations showed that foreshock transients also exist in the midtail foreshock, which can continuously disturb the nightside bow shock, magnetosheath, and magnetopause while propagating tailward for tens of minutes. To further understand the characteristics of midtail foreshock transients, we studied them statistically using Acceleration Reconnection Turbulence & Electrodynamics of Moon’s Interaction with the Sun observations. We selected 111 events that have dynamic pressure decrease along the local bow shock normal by more than 50%. We show that the dynamic pressure decrease is contributed by both density decrease and speed decrease. Around 90% of the events have electron temperature increase by more than 10% with a temperature change ratio proportional to the solar wind speed. Midtail foreshock transients more likely occur at the dawnside than the duskside. They are more significant closer to the bow shock and rather stable along the tailward direction. They have similar formation conditions compared to the dayside foreshock transients, except the ones related to the bow shock geometry. Our study indicates that the characteristics of foreshock transients based on dayside observations need to be generalized. Our study also implies that foreshock transients can exist for tens of minutes (even longer for larger planar shocks), continuously disturbing the local shock and accelerating/heating particles.

中文翻译：

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中尾前突中前突瞬变的统计研究

在白天的前震中，已经观察到并模拟了许多前震瞬变。由于其强烈的动态压力扰动，前震瞬变会干扰局部弓激波，磁石震荡，磁更年期，进而扰乱磁层-电离层系统。它们还可以加速导致冲击加速的粒子。最近的观察和模拟显示，中尾前震中还存在前震瞬变，当向尾传播数十分钟时，前瞬变可连续干扰夜间的弓首冲击，磁石震荡和磁更年期。为了进一步了解中尾前震瞬变的特征，我们使用加速重连湍流和月球与太阳相互作用的电动力学对它们进行了统计研究。我们选择了111个事件，这些事件的动态压力沿局部船首冲击法线下降了50％以上。我们表明，动压下降是由密度下降和速度下降共同造成的。大约90％的事件的电子温度升高超过10％，且温度变化率与太阳风速成正比。中尾前额瞬变更可能发生在黎明侧而不是黄昏侧。它们在靠近弓首冲击时更显着，并且在向后方向上更稳定。与白天前震瞬变相比，它们具有相似的形成条件，除了与弓激波几何相关的条件。我们的研究表明，基于日间观测的前震瞬变特征需要加以概括。