Although numerous works have concentrated on minifilament eruption in complex configurations, the detailed triggering mechanism is still an open question. Using the observational data from the New Vacuum Solar Telescope and Solar Dynamics Observatory, we studied a two-step magnetic reconnection process that triggered a minifilament that erupted intermittently within a fan-spine structure in the active region NOAA 13272. The first-step reconnection occurred between a set of low-lying small-scale magnetic loops and their nearby inner spine, resulting in the appearance of a brightening at the reconnection site and the reconfiguration of the inner spine. As the reconfigured inner spine approached the outer spine, reconnection occurred between them at the null point and led to the minifilament erupting partially. Subsequently, this two-step reconnection scenario occurred again and triggered the minifilament to erupt completely. The null point reconnection was supported by the changes in the topological structure of the inner spine and the outer spine, circular ribbon flares, remote brightenings, and the brightening of the outer spine. The null point reconnection related to the second eruption was also confirmed by some plasmoids expelled from the reconnection site. Further, the results of the magnetic field extrapolation reveal the existence of a fan-spine structure involving a three-dimensional null point. We suggest that the two-step reconnection triggers the two eruptions, in which the null point reconnection plays a direct role, but the dynamical evolution of the inner spine and the outer spine driven by the first-step reconnection might be a precursor of the subsequent null point reconnection.

中文翻译：

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由扇形脊结构中的两步磁重连接触发的两次微丝间歇性爆发


尽管许多工作都集中在复杂构型中的微丝喷发，但详细的触发机制仍然是一个悬而未决的问题。利用来自新真空太阳望远镜和太阳动力学天文台的观测数据，我们研究了一个两步磁重联过程，该过程触发了在活动区域 NOAA 13272 的扇脊结构内间歇性爆发的微丝。第一步重新连接发生在一组低洼的小规模磁环与其附近的内棘之间，导致重新连接部位出现变亮和内棘的重新配置。当重新配置的内棘接近外棘时，它们之间在零点发生重新连接，并导致微丝部分爆发。随后，这种两步重新连接的情况再次发生，并触发了微丝完全爆发。内棘和外棘拓扑结构的变化、圆形丝带耀斑、远程增亮和外棘的增亮都支持零点重连。与第二次喷发相关的零点重新连接也被一些从重新连接位点排出的等离子体证实。此外，磁场外推的结果揭示了涉及三维零点的扇脊结构的存在。我们认为两步重连触发了两次爆发，其中零点重连起直接作用，但第一步重连驱动的内脊和外脊的动态演变可能是后续零点重连的前兆。