标题： 地球准垂直激波中的非平稳性出现 显示英文标题

标题： Occurrence of Non-Stationarity at Earth's Quasi-Perpendicular Bow Shock

摘要： 碰撞无激波在稳定上游条件下也可能表现出非稳态行为，形成复杂的过渡区域。 与激波自重构和表面波动相关的离子相空间洞是这种非稳态的特征。 我们使用地球准垂直弓激波的521次穿越进行统计分析。 相空间洞出现在65%的情况下，尽管实际发生率可能更高，因为在快速激波穿越过程中这些洞可能无法被分辨。 对于阿尔芬马赫数为$M_A>7$的激波，发生率达到70%。 这些发现表明，地球的准垂直弓激波主要是非稳态的。 显示英文摘要

摘要： Collisionless shocks can exhibit non-stationary behavior even under steady upstream conditions, forming a complex transition region. Ion phase-space holes, linked to shock self-reformation and surface ripples, are a signature of this non-stationarity. We statistically analyze their occurrence using 521 crossings of Earth's quasi-perpendicular bow shock. Phase-space holes appear in 65% of cases, though the actual rate may be higher as the holes may not be resolved during fast shock crossings. The occurrence rate peaks at 70% for shocks with Alfv\'en Mach numbers $M_A>7$. These findings suggest that Earth's quasi-perpendicular bow shock is predominantly non-stationary.