A kinetic-scale magnetic hole in the magnetopause reconnection separatrix region

Magnetic holes are ubiquitous in Earth's magnetosphere plasma system. Understanding their formation mechanisms and influence to background plasma is crucial for insight into energy conversion in near-earth space environments. Here, we present unambiguous evidence that a kinetic-scale magnetic hole occurs in the separatrix region of asymmetry reconnection at the Earth's magnetopause, implying that the connection between magnetic holes and reconnection should be more extensive. By taking advantage of high-resolution measurements, we show that electrons along the separatrix region are trapped and significantly thermalized by magnetic hole. Observations suggest that separatrix region with significant shear flow can provide favourable conditions for stable magnetic holes, which can further continuously generate high-energy electrons.