Particle acceleration in explosive relativistic reconnection events and Crab Nebula gamma-ray flares
Particle acceleration in explosive relativistic reconnection events and Crab Nebula gamma-ray flares
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爆炸性相对论重联事件和蟹状星云伽马射线耀斑中的粒子加速
DOI：
10.1017/s0022377818000168
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
O. Porth
中科院分区：
文献类型：
--
作者：
M. Lyutikov;L. Sironi;S. Komissarov;O. Porth
我们发展了一个相对论磁控等离子体中爆炸重联事件中粒子加速的模型，并用它解释了蟹状星云的伽马射线耀斑。该模型依赖于宏观尺度上电流驱动不稳定性的发展(与等离子体皮肤深度无关)。利用解析和数值方法(流体和粒子模拟)，我们研究了相对论磁控等离子体中的一些模型问题：(I)我们将Syrovatsky的经典爆炸X点崩塌模型推广到磁控等离子体中；(Ii)我们考虑了二维无力磁通量管系统的不稳定性；(Iii)我们考虑了两个零总极向电流磁通量管的合并。在所有情况下，都研究了自发进化和驱动进化的机制。我们确定了粒子加速的两个阶段：(I)快速爆炸的快速X点坍塌和(Ii)随后的岛屿合并。最快的加速发生在最初灾难性的X点崩塌期间，重联电场的量级是磁场。重新连接的爆炸性阶段产生非热幂定律尾部，其斜率取决于平均磁化强度。X点崩塌阶段之后是磁岛合并，在强制重联的情况下，磁岛合并耗散了很大一部分初始磁能，进一步加速了粒子，但重联速度较慢。蟹状耀斑是由中极区星云主体中产生的磁通量管在磁岛合并的初始爆炸阶段产生的。在温和磁化的风扇区中，终止后激波等离子体流动自然产生大尺度的高磁化结构。内部扭结状的不稳定性导致宏观载流磁通管的形成，并以爆炸式的方式合并。
We develop a model of particle acceleration in explosive reconnection events in relativistic magnetically-dominated plasmas and apply it to explain gamma-ray flares from the Crab Nebula. The model relies on development of current-driven instabilities on macroscopic scales (not related to plasma skin depths). Using analytical and numerical methods (fluid and particle-in-cell simulations), we study a number of model problems in relativistic magnetically-dominated plasma: (i) we extend Syrovatsky's classical model of explosive X-point collapse to magnetically-dominated plasmas; (ii) we consider instability of two-dimensional force-free system of magnetic flux tubes; (iii) we consider merger of two zero total poloidal current magnetic flux tubes. In all cases regimes of spontaneous and driven evolution are investigated. We identify two stages of particle acceleration: (i) fast explosive prompt X-point collapse and (ii) ensuing island merger. The fastest acceleration occurs during the initial catastrophic X-point collapse, with the reconnection electric field of the order of the magnetic field. The explosive stage of reconnection produces non-thermal power-law tails with slopes that depend on the average magnetization. The X-point collapse stage is followed by magnetic island merger that dissipates a large fraction of the initial magnetic energy in a regime of forced reconnection, further accelerating the particles, but proceeds at a slower reconnection rate. Crab flares result from the initial explosive stages of magnetic island mergers of magnetic flux tubes produced in the bulk of nebula at intermediate polar regions. The post-termination shock plasma flow in the wind sectors with mild magnetization naturally generates large-scale highly magnetized structures. Internal kink-like instabilities lead to the formation of macroscopic current-carrying magnetic flux tubes that merge explosively.
影响因子：
4.8
作者：
S. Komissarov
通讯作者：
S. Komissarov