Du Senbei, Zank Gary P, Li Xiaocan, Guo Fan
Department of Space Science, University of Alabama in Huntsville, Huntsville, Alabama 35899, USA.
Department of Space Science, University of Alabama in Huntsville, Huntsville, Alabama 35899, USA and Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, Alabama 35805, USA.
Phys Rev E. 2020 Mar;101(3-1):033208. doi: 10.1103/PhysRevE.101.033208.
It is well known that collisionless systems are dissipation free from the perspective of particle collision and thus conserve entropy. However, processes such as magnetic reconnection and turbulence appear to convert large-scale magnetic energy into heat. In this paper, we investigate the energization and heating of collisionless plasma. The dissipation process is discussed in terms of fluid entropy in both isotropic and gyrotropic forms. Evolution equations for the entropy are derived and they reveal mechanisms that lead to changes in fluid entropy. These equations are verified by a collisionless particle-in-cell simulation of multiple reconnecting current sheets. In addition to previous findings regarding the pressure tensor, we emphasize the role of heat flux in the dissipation process.
众所周知，从粒子碰撞的角度来看，无碰撞系统是无耗散的，因此熵守恒。然而，诸如磁重联和湍流等过程似乎会将大规模磁能转化为热量。在本文中，我们研究无碰撞等离子体的能量激发和加热。从各向同性和旋转变换形式的流体熵的角度讨论了耗散过程。推导了熵的演化方程，这些方程揭示了导致流体熵变化的机制。通过对多个重联电流片的无碰撞粒子模拟验证了这些方程。除了之前关于压力张量的发现外，我们强调了热通量在耗散过程中的作用。
