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arXiv 2203.04320astro-ph.HE
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电磁烟花:压缩磁星风中快速重联产生的快速射电暴

Electromagnetic fireworks: Fast radio bursts from rapid reconnection in the compressed magnetar wind

J. F. Mahlmann, A. A. Philippov, A. Levinson, A. Spitkovsky, H. Hakobyan

摘要:

产生快速射电暴(FRB)的一种情况是磁星风电流片中的磁重联。在磁星耀斑产生的强磁脉冲的压缩下,电流片分裂成自相似的磁岛链。在它们的分层聚结过程中,在它们的界面处的随时间变化的等离子体电流产生相干辐射。我们研究这种情况下,使用二维辐射相对论粒子在细胞模拟计算效率的相干发射,并获得频率定标。与预期一致的是,一小部分重新连接的磁场能量,$f\sim 0.002$,被转换为高频快磁声波包,可以从磁星风中逃逸为无线电发射。在协议与分析估计,我们发现,磁脉冲的$10^{47}\text{erg}\;\text{s}^{-1}$可以触发相对窄带GHz的发光度约为$10^{42}\text{erg}\;\text{s}^{-1}$,足以解释明亮的河外FRB。该机制为突发信号的向下频率漂移以及最近在FRB 20200120 E中检测到的$\sim 100\;\text{ns}$子结构提供了自然的解释。

英文摘要:

One scenario for the generation of fast radio bursts (FRBs) is magnetic reconnection in a current sheet of the magnetar wind. Compressed by a strong magnetic pulse induced by a magnetar flare, the current sheet fragments into a self-similar chain of magnetic islands. Time-dependent plasma currents at their interfaces produce coherent radiation during their hierarchical coalescence. We investigate this scenario using 2D radiative relativistic particle-in-cell simulations to compute the efficiency of the coherent emission and to obtain frequency scalings. Consistent with expectations, a fraction of the reconnected magnetic field energy, $f\sim 0.002$, is converted to packets of high-frequency fast magnetosonic waves which can escape from the magnetar wind as radio emission. In agreement with analytical estimates, we find that magnetic pulses of $10^{47}\text{erg}\;\text{s}^{-1}$ can trigger relatively narrowband GHz emission with luminosities of approximately $10^{42}\text{erg}\;\text{s}^{-1}$, sufficient to explain bright extragalactic FRBs. The mechanism provides a natural explanation for a downward frequency drift of burst signals, as well as the $\sim 100\;\text{ns}$ substructure recently detected in FRB 20200120E.

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