The first multimessenger observation of a binary neutron star (BNS) merger in August 2017 demonstrated the huge scientific potential of these extraordinary events. This breakthrough led to a number of discoveries and provided the best evidence that BNS mergers can launch short gamma-ray burst (SGRB) jets and are responsible for a copious production of heavy r-process elements. On the other hand, the details of the merger and post-merger dynamics remain only poorly constrained, leaving behind important open questions. Numerical relativity simulations are a powerful tool to unveil the physical processes at work in a BNS merger and as such they offer the best chance to improve our ability to interpret the corresponding gravitational wave (GW) and electromagnetic emission. Here, we review the current theoretical investigation on BNS mergers based on general relativistic magnetohydrodynamics simulations, paying special attention to the magnetic field as a crucial ingredient. First, we discuss the evolution, amplification, and emerging structure of magnetic fields in BNS mergers. Then, we consider their impact on various critical aspects: (i) jet formation and the connection with SGRBs, (ii) matter ejection, r-process nucleosynthesis, and radioactively-powered kilonova transients, and (iii) post-merger GW emission.

中文翻译：

---

磁场在双中子星并合中的关键作用

2017 年 8 月对双中子星 (BNS) 合并的首次多信使观测证明了这些非凡事件的巨大科学潜力。这一突破导致了许多发现，并提供了最好的证据，证明 BNS 合并可以发射短伽马射线爆发 (SGRB) 射流，并负责大量生产重 r 过程元素。另一方面，合并和合并后动态的细节仍然很少受到限制，留下了重要的悬而未决的问题。数值相对论模拟是揭示 BNS 合并中起作用的物理过程的强大工具，因此它们为提高我们解释相应引力波 (GW) 和电磁辐射的能力提供了最佳机会。这里，我们回顾了基于一般相对论磁流体动力学模拟的 BNS 合并的当前理论研究，特别关注磁场作为关键因素。首先，我们讨论了 BNS 合并中磁场的演化、放大和新兴结构。然后，我们考虑它们对各个关键方面的影响：(i) 喷射形成和与短暴的连接，(ii) 物质喷射、r 过程核合成和放射性驱动的千新星瞬变，以及 (iii) 合并后的 GW 发射。