High-energy synchrotron flares powered by strongly radiative relativistic magnetic reconnection: 2D and 3D PIC simulations
High-energy synchrotron flares powered by strongly radiative relativistic magnetic reconnection: 2D and 3D PIC simulations
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DOI：
10.1093/mnras/stad1588
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发表时间：
2023-03
影响因子：
4.8
通讯作者：
K. Schoeffler;T. Grismayer;D. Uzdensky;L. Silva
中科院分区：
文献类型：
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作者：
K. Schoeffler;T. Grismayer;D. Uzdensky;L. Silva
用二维和三维(2D和3D)粒子单元(PIC)模拟研究了强磁场重联激励的相对论对等离子体中高能同步辐射的时间演化。用辐射PIC程序OSIRIS进行了2D/3D比较研究，该程序自洽地考虑了发射粒子上的同步辐射反应，并使我们能够探索同步辐射冷却的影响。磁重联导致磁岛(等离子体类)内部的等离子体和磁场被压缩，导致耀斑发射增强，这可能有助于解释一些天体物理伽马射线耀斑的观测。虽然辐射冷却减弱了等离子体核的发射，但它促进了那里的额外压缩，进一步放大了磁场B和等离子体密度n，从而部分地缓解了这种影响。开发了利用n-B空间中的2D直方图的新的模拟诊断方法，并用于可视化和量化压缩的影响。观察到n-B直方图以相对尖锐的幂定律边界为界，这标志着对压缩的明确限制。对其中一些压缩极限进行了理论解释，其根源在于辐射电阻率或3D扭结不稳定性。关于引导磁场、系统大小和上游磁化强度的系统参数空间研究表明，在具有更大重联区大小和更高磁化强度的环境中，特别是当磁场强度接近临界(Schwinger)场时，可能发生更强的压缩、更明亮的高能辐射，以及可能是显著的量子电动力学(QED)效应，如在磁磁层中发现的那样。
The time evolution of high-energy synchrotron radiation generated in a relativistic pair plasma energized by reconnection of strong magnetic fields is investigated with two- and three-dimensional (2D and 3D) particle-in-cell (PIC) simulations. The simulations in this 2D/3D comparison study are conducted with the radiative PIC code OSIRIS, which self-consistently accounts for the synchrotron radiation reaction on the emitting particles, and enables us to explore the effects of synchrotron cooling. Magnetic reconnection causes compression of the plasma and magnetic field deep inside magnetic islands (plasmoids), leading to an enhancement of the flaring emission, which may help explain some astrophysical gamma-ray flare observations. Although radiative cooling weakens the emission from plasmoid cores, it facilitates additional compression there, further amplifying the magnetic field B and plasma density n, and thus partially mitigating this effect. Novel simulation diagnostics utilizing 2D histograms in the n-B space are developed and used to visualize and quantify the effects of compression. The n-B histograms are observed to be bounded by relatively sharp power-law boundaries marking clear limits on compression. Theoretical explanations for some of these compression limits are developed, rooted in radiative resistivity or 3D kinking instabilities. Systematic parameter-space studies with respect to guide magnetic field, system size, and upstream magnetization are conducted and suggest that stronger compression, brighter high-energy radiation, and perhaps significant quantum electrodynamic (QED) effects such as pair production, may occur in environments with larger reconnection-region sizes and higher magnetization, particularly when magnetic field strengths approach the critical (Schwinger) field, as found in magnetar magnetospheres.