The prebreakup arc at the inner edge of the auroral boundary is intensified upon arrival of an auroral streamer—the ionospheric signature of the earthbound mesoscale plasma flows (MPF). Yet the cause of electron precipitation enhancement only in this region remains unclear. We suggest that the intensified precipitation comes from the turbulent plasmasphere boundary layer (TPBL) that forms due to short circuiting of MPFs over the presubstorm plasmapause and overlaps with the plasma sheet (PS) inner boundary. Resonance interaction of the PS electrons with intense low‐frequency plasma waves leads to enhanced precipitation from this narrow region. Indeed, the DMSP spacecraft observations near the substorm onset show intensified electron fluxes in a narrow region near the auroral boundary, which maps into the TPBL. The same pattern observed in conjunction with postonset auroral streamers points to the common mechanism, which is the short‐circuiting process. Therefore, we suggest that the enhanced precipitation into the prebreakup arc is causally related to the MPFs' short circuiting over the plasmapause.

中文翻译：

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血浆中等离子血浆流短路导致的破裂前电弧增强

当极光拖缆到达时，极光边界内边缘的预破裂弧增强了-地球上的中尺度等离子流（MPF）的电离层特征。然而，仅在该区域中电子沉淀增强的原因仍不清楚。我们认为降水的增加来自湍流的等离子层边界层（TPBL），这是由于亚暴前等离子区暂停前MPF的短路而形成的，并且与等离子层（PS）的内边界重叠。PS电子与强烈的低频等离子体波的共振相互作用导致该狭窄区域的降水增加。实际上，亚暴爆发附近的DMSP航天器观测结果表明，在极光边界附近的狭窄区域中电子通量增强，并映射到TPBL中。结合发病后极光彩带观察到的相同模式指出了共同的机制，这就是短路过程。因此，我们认为进入预破裂弧的降水增加与MPF在血浆暂停期间的短路有因果关系。