The synchrotron maser emission from relativistic shocks in Fast Radio Bursts: 1D PIC simulations of cold pair plasmas
The synchrotron maser emission from relativistic shocks in Fast Radio Bursts: 1D PIC simulations of cold pair plasmas
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DOI：
10.1093/mnras/stz640
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发表时间：
2019-01
影响因子：
4.8
通讯作者：
I. Plotnikov;L. Sironi
中科院分区：
文献类型：
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作者：
I. Plotnikov;L. Sironi
快速射电暴（frb）的发射过程仍然未知。我们研究了磁星风中相对论性激波的同步微波激射能否解释观测到的快速射电暴特性。我们执行粒子在细胞（PIC）模拟垂直冲击在冷对等离子体，检查我们的结果之间的一致性三个PIC代码。我们证实了线偏振x模波是由激波自一致产生的，并作为前驱波逆流传播。我们发现，在磁化σ≥1（即波印廷通量与预激波流的粒子能量通量之比）时，激波将总入射能量$f_\xi ^{\prime } \approx 7 \times 10^{-4}/\sigma ^2$的一小部分转化为前驱波，如激波框架中测量的那样。波谱是窄带的（分数宽度为1−3），具有明显但不主要的线状特征，因为许多共振同时起作用。预冲击（观测器）帧的峰值频率为$\omega ^{\prime \prime }_{\rm peak} \approx 3 \gamma _{\rm s | u} \omega _{\rm p}$，其中γs|u为上游帧的激波洛伦兹因子，ωp为等离子体频率。在σ≥1处，我们估计的$\omega ^{\prime \prime }_{\rm peak}$与先前的研究结果不同，激波结构表现为两个被空腔隔开的孤子，并且峰值频率对应于空腔的特征模态。我们的研究结果为磁星情景下的快速射电暴发射模型提供了物理接地输入。
The emission process of Fast Radio Bursts (FRBs) remains unknown. We investigate whether the synchrotron maser emission from relativistic shocks in a magnetar wind can explain the observed FRB properties. We perform particle-in-cell (PIC) simulations of perpendicular shocks in cold pair plasmas, checking our results for consistency among three PIC codes. We confirm that a linearly polarized X-mode wave is self-consistently generated by the shock and propagates back upstream as a precursor wave. We find that at magnetizations σ ≳ 1 (i.e. ratio of Poynting flux to particle energy flux of the pre-shock flow) the shock converts a fraction $f_\xi ^{\prime } \approx 7 \times 10^{-4}/\sigma ^2$ of the total incoming energy into the precursor wave, as measured in the shock frame. The wave spectrum is narrow-band (fractional width ≲1−3), with apparent but not dominant line-like features as many resonances concurrently contribute. The peak frequency in the pre-shock (observer) frame is $\omega ^{\prime \prime }_{\rm peak} \approx 3 \gamma _{\rm s | u} \omega _{\rm p}$, where γs|u is the shock Lorentz factor in the upstream frame and ωp the plasma frequency. At σ ≳ 1, where our estimated $\omega ^{\prime \prime }_{\rm peak}$ differs from previous works, the shock structure presents two solitons separated by a cavity, and the peak frequency corresponds to an eigenmode of the cavity. Our results provide physically grounded inputs for FRB emission models within the magnetar scenario.