DIFFUSIVE SHOCK ACCELERATION AT COSMOLOGICAL SHOCK WAVES
DIFFUSIVE SHOCK ACCELERATION AT COSMOLOGICAL SHOCK WAVES
复制标题
DOI：
10.1088/0004-637x/764/1/95
复制
发表时间：
2012-12
期刊：
影响因子：
--
通讯作者：
Hyesung Kang;D. Ryu
中科院分区：
文献类型：
--
作者：
Hyesung Kang;D. Ryu
我们重新审视非线性扩散冲击加速（DSA）在宇宙的大尺度结构的宇宙学冲击，将波粒子相互作用，预计在无碰撞冲击。采用简单的唯象模型的磁场放大（MFA）的宇宙射线（CR）流不稳定性和Alfvénic漂移，我们进行动力学DSA模拟的范围很广的音速和Alfvénic马赫数，并评估CR注入分数和加速效率。在我们的DSA模型中，CR加速效率主要取决于音速马赫数Ms，而MFA因子则取决于Alfvénic马赫数和CR对激波的修正程度。我们表明，在强CR修改冲击，如果散射中心漂移与有效的阿尔文速度在放大磁场，CR能谱变陡，加速效率显着降低，相比，没有这样的效果的情况下。因此，对于Ms = 10的强地震，震后CR压力大约在地震冲压压力的20%处饱和。在试验粒子区域（Ms = 3），预计磁场不会被放大，Alfvénic漂移效应是微不足道的，尽管在低马赫数冲击下的相关等离子体物理过程仍然很大程度上不确定。
We reexamine nonlinear diffusive shock acceleration (DSA) at cosmological shocks in the large-scale structure of the universe, incorporating wave–particle interactions that are expected to operate in collisionless shocks. Adopting simple phenomenological models for magnetic field amplification (MFA) by cosmic-ray (CR) streaming instabilities and Alfvénic drift, we perform kinetic DSA simulations for a wide range of sonic and Alfvénic Mach numbers and evaluate the CR injection fraction and acceleration efficiency. In our DSA model, the CR acceleration efficiency is determined mainly by the sonic Mach number Ms, while the MFA factor depends on the Alfvénic Mach number and the degree of shock modification by CRs. We show that at strong CR modified shocks, if scattering centers drift with an effective Alfvén speed in the amplified magnetic field, the CR energy spectrum is steepened and the acceleration efficiency is reduced significantly, compared to the cases without such effects. As a result, the postshock CR pressure saturates roughly at ∼20% of the shock ram pressure for strong shocks with Ms ≳ 10. In the test-particle regime (Ms ≲ 3), it is expected that the magnetic field is not amplified and the Alfvénic drift effects are insignificant, although relevant plasma physical processes at low Mach number shocks remain largely uncertain.