On magnetic field amplification and particle acceleration near non-relativistic astrophysical shocks: particles in MHD cells simulations
On magnetic field amplification and particle acceleration near non-relativistic astrophysical shocks: particles in MHD cells simulations
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DOI：
10.1093/mnras/stx2509
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发表时间：
2017-09
影响因子：
4.8
通讯作者：
A. J. Marle;F. Casse;A. Marcowith
中科院分区：
文献类型：
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作者：
A. J. Marle;F. Casse;A. Marcowith
我们提出了磁化天体物理冲击的模拟，考虑到热等离子体的冲击和超热粒子之间的相互作用。这种相互作用的描述相结合的网格为基础的磁流体动力学描述的热流体与粒子在细胞技术致力于超热粒子的动力学。这种方法结合了自适应网格细化功能的使用，可能是在空间尺度上模拟天体物理系统的关键，而空间尺度超出了纯粹的粒子模拟的范围。在这项研究中，我们考虑了非相对论冲击与各种Alfvenic马赫数和磁场强度。当磁场平行于激波法线时，我们恢复了以前研究中磁场放大和粒子加速的所有特征。与以前的粒子在细胞混合模拟相比，我们发现，粒子加速和磁场放大也发生时，磁场是倾斜的冲击，但在更大的时间尺度比平行的情况下。我们表明，在我们的模拟中，超热粒子正在经历加速由于粒子的预热过程类似于冲击漂移加速导致的冲击波前。冲击波阵面和磁场的这种振荡局部地帮助粒子进入上游区域，并引发非共振流不稳定性，并最终诱导扩散粒子加速。
We present simulations of magnetized astrophysical shocks taking into account the interplay between the thermal plasma of the shock and suprathermal particles. Such interaction is depicted by combining a grid-based magnetohydrodynamics description of the thermal fluid with particle in cell techniques devoted to the dynamics of suprathermal particles. This approach, which incorporates the use of adaptive mesh refinement features, is potentially a key to simulate astrophysical systems on spatial scales that are beyond the reach of pure particle-in-cell simulations. We consider in this study non-relativistic shocks with various Alfvenic Mach numbers and magnetic field obliquity. We recover all the features of both magnetic field amplification and particle acceleration from previous studies when the magnetic field is parallel to the normal to the shock. In contrast with previous particle-in-cell-hybrid simulations, we find that particle acceleration and magnetic field amplification also occur when the magnetic field is oblique to the normal to the shock but on larger time-scales than in the parallel case. We show that in our simulations, the suprathermal particles are experiencing acceleration thanks to a pre-heating process of the particle similar to a shock drift acceleration leading to the corrugation of the shock front. Such oscillations of the shock front and the magnetic field locally help the particles to enter the upstream region and to initiate a non-resonant streaming instability and finally to induce diffuse particle acceleration.